These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

L-Leucine and L-isoleucine enhance growth of BBN-induced urothelial tumors in the rat bladder by modulating expression of amino acid transporters and tumorigenesis-associated genes.  

PubMed

We investigated the underlying mechanisms of L-leucine and L-isoleucine mediated promotion of bladder carcinogenesis using an initiation-promotion model. Rats were administered N-butyl-N-(4-hydroxybutyl) nitrosamine for 4 weeks and then fed AIN-93G basal diet or diet supplemented with L-leucine or L-isoleucine for 8 weeks followed by the basal diet for another 8 weeks. At the end of the experiment, week 20, there was a significant elevation of papillary and nodular (PN) hyperplasia multiplicity in the amino acid groups. L-Leucine and L-isoleucine transporters were up-regulated in PN hyperplasias and/or bladder tumors compared with concomitant normal-appearing bladder urothelium at weeks 12 and/or 20 in all groups. In addition, in normal-appearing bladder urothelium, significantly increased mRNA levels of y+LAT1, LAT2, LAT4, and 4F2hc were observed in the amino acid groups compared with the BBN control group at both weeks 12 and 20, and increased mRNA levels of LAT1 were observed at week 20. Furthermore, up-regulation of TNF-?, c-fos, ?-catenin, p53, p21(Cip1/WAF1), cdk4, cyclin D1 and caspase 3 in the amino acid groups was detected in normal-appearing bladder urothelium. Overall, our results indicate that supplementation with l-leucine or l-isoleucine enhanced growth of bladder urothelial tumors by triggering expression of amino acid transporters and tumorigenesis-associated genes. PMID:23747718

Xie, Xiao-Li; Kakehashi, Anna; Wei, Min; Yamano, Shotaro; Takeshita, Masanori; Yunoki, Takayuki; Wanibuchi, Hideki

2013-09-01

2

Improvement of an l-Leucine-Producing Mutant of Brevibacterium lactofermentum 2256 by Genetically Desensitizing It to ?-Acetohydroxy Acid Synthetase  

PubMed Central

Genetic improvement of l-leucine productivity in strain 218, an ile? 2-thiazolealanine-resistant mutant of Brevibacterium lactofermentum 2256, was attempted. In strain 218, which produced 28 mg of l-leucine per ml from 13% glucose, ?-isopropylmalate synthetase was genetically desensitized and derepressed to the effect of l-leucine, whereas ?-acetohydroxy acid synthetase remained unaltered, although it could be derepressed phenotypically by limiting the isoleucine concentration in the culture. From strain 218 we isolated 103 mutants resistant to ?-hydroxyleucine (4 mg/ml). Among these, three were found to produce mere l-leucine than the parent. The ?-acetohydroxy acid synthetase of all three mutant strains was found to be genetically desensitized to all of the branched-chain amino acids l-isoleucine, l-valine, and l-leucine. The repression mechanism in ?-acetohydroxy acid synthetase formation was the same as in the parent strain. The improved strains typically produced 34 mg of l-leucine per ml, the highest productivity ever reported. PMID:16347048

Tsuchida, Takayasu; Momose, Haruo

1986-01-01

3

Characterization of Bacillus thuringiensis l-Isoleucine Dioxygenase for Production of Useful Amino Acids?†  

PubMed Central

We determined the enzymatic characteristics of an industrially important biocatalyst, ?-ketoglutarate-dependent l-isoleucine dioxygenase (IDO), which was found to be the enzyme responsible for the generation of (2S,3R,4S)-4-hydroxyisoleucine in Bacillus thuringiensis 2e2. Depending on the amino acid used as the substrate, IDO catalyzed three different types of oxidation reactions: hydroxylation, dehydrogenation, and sulfoxidation. IDO stereoselectively hydroxylated several hydrophobic aliphatic l-amino acids, as well as l-isoleucine, and produced (S)-3-hydroxy-l-allo-isoleucine, 4-hydroxy-l-leucine, (S)-4-hydroxy-l-norvaline, 4-hydroxy-l-norleucine, and 5-hydroxy-l-norleucine. The IDO reaction product of l-isoleucine, (2S,3R,4S)-4-hydroxyisoleucine, was again reacted with IDO and dehydrogenated into (2S,3R)-2-amino-3-methyl-4-ketopentanoate, which is also a metabolite found in B. thuringiensis 2e2. Interestingly, IDO catalyzed the sulfoxidation of some sulfur-containing l-amino acids and generated l-methionine sulfoxide and l-ethionine sulfoxide. Consequently, the effective production of various modified amino acids would be possible using IDO as the biocatalyst. PMID:21821743

Hibi, Makoto; Kawashima, Takashi; Kodera, Tomohiro; Smirnov, Sergey V.; Sokolov, Pavel M.; Sugiyama, Masakazu; Shimizu, Sakayu; Yokozeki, Kenzo; Ogawa, Jun

2011-01-01

4

Molecular Structure of L-Isoleucine  

NSDL National Science Digital Library

L-Isoleucine is an essential, branched-chain, aliphatic amino acid that is found in many proteins. It is an important compound for hemoglobin synthesis and regulates energy and blood sugar levels. Together with leucine and valine, it metabolizes in muscle tissue and promotes muscle recovery, wound healing, including the growth of new tissue and increases growth hormone production. Only the L-form occurs in mammalian protein.

2002-08-20

5

Nucleating characteristics of Pseudomonas aeruginosa above 0 °C and the role of L-leucine  

NASA Astrophysics Data System (ADS)

It has been reported earlier that the bacteria Pseudomonas aeruginosa have the ability to nucleate ice over a long temperature range below 0 °C. In the present work, the same bacteria are shown to have nucleating ability even above 0 °C. It is found to reach a peak at 4 °C and then gradually falls off as the temperature is raised, vanishing altogether at 12 °C. When the bacteria are irradiated by UV-rays, the nucleating ability above 0 °C has the same variational pattern with change of temperature, though the ability is significantly less. When the bacterial medium is boiled for 20 min, the bacteria loose their nucleating ability completely. Since ice cannot exist above 0 °C, some supporting experiments are performed to establish the identity of the nucleated crystals: Crystals grown around a small sample of cultured P. aeruginosa in an incubator were shown to be identical with the nucleated crystals in the Cold Room experiments. X-ray diffraction (XRD) spectrum of the grown crystals is found to be consistent with the presence of amino acids like L-leucine, isoleucine and L-isoleucine, amongst which L-leucine is the most abundant. When droplets of an aqueous solution of L-leucine are seeded, their nucleation characteristics are similar to those with P. aeruginosa. From XRD, nuclear magnetic resonance (NMR) and thermal analysis, one can conclude that the crystals formed by P. aeruginosa above 0 °C are hydrate crystals with water phase caging around the seeded agent; the amino acid L-leucine present in the protein of the bacteria plays the dominant role in the nucleation.

Hazra, Anupam; De, U. K.; Goswami, K.

2006-01-01

6

L-Valine Ester of Cyclopropavir - a New Antiviral Prodrug  

PubMed Central

The L-Valine ester of antiviral agent cyclopropavir, valcyclopropavir (6), was synthesized and evaluated for antiviral properties. Prodrug (6) inhibited replication of HCMV virus (Towne and AD169 strain) in HFF cells to approximately the same extent as the parent drug cyclopropavir (5). Stability of 6 toward hydrolysis at pH 7.0 roughly corresponds to that of valganciclovir (2). Pharmacokinetic studies in mice established that the oral bioavailability of valcyclopropavir (6) was 95%. PMID:19794230

Wu, Zhimeng; Drach, John C.; Prichard, Mark N.; Yanachkova, Milka; Yanachkov, Ivan; Bowlin, Terry L.; Zemlicka, Jiri

2010-01-01

7

Absence d'effets de l'injection de surcharges de L-valine et L-leucine sur les teneurs plasmatiques en insuline  

E-print Network

en insuline et en glucagon de l'agneau préruminant D. ATTAIX Isabelle PAPET J. GRIZARD M. ARNAL.) had no effect on insulin and glucagon levels in plasma from fed or 10-hour starved preruminant lambs-leucine sur les teneurs plasmatiques en insuline et en glucagon de l'agneau préruminant. De telles injections

Boyer, Edmond

8

Possibility of wound dressing using poly( l-leucine)\\/poly(ethylene glycol)\\/poly( l-leucine) triblock copolymer  

Microsoft Academic Search

ABA-type block copolymers (abbreviated as LEL) composed of poly(l-leucine) (PLL) as the A component and poly(ethylene glycol) (PEG) as the B component were synthesized by ring-opening polymerization of l-leucine N-carboxyanhydride initiated by primary amino group located at both ends of PEG chain. A silver sulfadiazine (AgSD)-impregnated wound dressing of sponge type was prepared by the lyophilization method. Morphological structure of

Hyun-Jung Kim; Eun-Young Choi; Jong-Suk Oh; Hyun-Chul Lee; Sung-Sik Park; Chong-Su Cho

2000-01-01

9

Improvement of the Redox Balance Increases l-Valine Production by Corynebacterium glutamicum under Oxygen Deprivation Conditions  

PubMed Central

Production of l-valine under oxygen deprivation conditions by Corynebacterium glutamicum lacking the lactate dehydrogenase gene ldhA and overexpressing the l-valine biosynthesis genes ilvBNCDE was repressed. This was attributed to imbalanced cofactor production and consumption in the overall l-valine synthesis pathway: two moles of NADH was generated and two moles of NADPH was consumed per mole of l-valine produced from one mole of glucose. In order to solve this cofactor imbalance, the coenzyme requirement for l-valine synthesis was converted from NADPH to NADH via modification of acetohydroxy acid isomeroreductase encoded by ilvC and introduction of Lysinibacillus sphaericus leucine dehydrogenase in place of endogenous transaminase B, encoded by ilvE. The intracellular NADH/NAD+ ratio significantly decreased, and glucose consumption and l-valine production drastically improved. Moreover, l-valine yield increased and succinate formation decreased concomitantly with the decreased intracellular redox state. These observations suggest that the intracellular NADH/NAD+ ratio, i.e., reoxidation of NADH, is the primary rate-limiting factor for l-valine production under oxygen deprivation conditions. The l-valine productivity and yield were even better and by-products derived from pyruvate further decreased as a result of a feedback resistance-inducing mutation in the acetohydroxy acid synthase encoded by ilvBN. The resultant strain produced 1,470 mM l-valine after 24 h with a yield of 0.63 mol mol of glucose?1, and the l-valine productivity reached 1,940 mM after 48 h. PMID:22138982

Hasegawa, Satoshi; Uematsu, Kimio; Natsuma, Yumi; Suda, Masako; Hiraga, Kazumi; Jojima, Toru; Inui, Masayuki

2012-01-01

10

L-Leucine and NO-mediated cardiovascular function.  

PubMed

Reduced availability of nitric oxide (NO) in the vasculature is a major factor contributing to the impaired action of insulin on blood flow and, therefore, insulin resistance in obese and diabetic subjects. Available evidence shows that vascular insulin resistance plays an important role in the pathogenesis of cardiovascular disease, the leading cause of death in developed nations. Interestingly, increased concentrations of L-leucine in the plasma occur in obese humans and other animals with vascular dysfunction. Among branched-chain amino acids, L-leucine is unique in inhibiting NO synthesis from L-arginine in endothelial cells and may modulate cardiovascular homeostasis in insulin resistance. Results of recent studies indicate that L-leucine is an activator of glutamine:fructose-6-phosphate aminotransferase (GFAT), which is the first and a rate-controlling enzyme in the synthesis of glucosamine (an inhibitor of endothelial NO synthesis). Through stimulating the mammalian target of rapamycin signaling pathway and thus protein synthesis, L-leucine may enhance GFAT protein expression, thereby inhibiting NO synthesis in endothelial cells. We propose that reducing circulating levels of L-leucine or endothelial GFAT activity may provide a potentially novel strategy for preventing and/or treating cardiovascular disease in obese and diabetic subjects. Such means may include dietary supplementation with either ?-ketoglutarate to enhance the catabolism of L-leucine in the small intestine and other tissues or with N-ethyl-L-glutamine to inhibit GFAT activity in endothelial cells. Preventing leucine-induced activation of GFAT by nutritional supplements or pharmaceutical drugs may contribute to improved cardiovascular function by enhancing vascular NO synthesis. PMID:25552397

Yang, Ying; Wu, Zhenlong; Meininger, Cynthia J; Wu, Guoyao

2015-03-01

11

Growth and characterization of l-valine doped tgs single crystals  

Microsoft Academic Search

Dielectric and pyroelectric properties were investigated for L-valine (LV) doped triglycine sulphate (LVTGS) single crystals grown by a slow cooling technique from LV (10 mol% and 20 mol%) doped TGS aqueous solution. Extremely high permittivity maxima (e.g. Kmax = 376,531 at 100 Hz) were observed at the secondary phase transition temperature (Tc = 49°C), presumably related to specific hydrogen bonds

S. Erdei; B. M. Jin; A. S. Bhalla; F. W. Ainger

1995-01-01

12

The effects of phospholipids on the activation of glutamate dehydrogenase by L-leucine.  

PubMed Central

Glutamate dehydrogenase in disrupted mitochondrial preparations is activated by L-leucine to a much greater extent than is the purified enzyme. A factor, or factors, responsible for modulating the sensitivity of L-leucine is lost during the purification of the enzyme. Although both cardiolipin and phosphatidylserine are inhibitors of the enzyme, only the inhibition by the former phospholipid is reversed by L-leucine. The inhibition of glutamate dehydrogenase by its binding to cardiolipin in the disrupted mitochondrial preparations and its relief by L-leucine could account for the greater sensitivity of such preparations to activation by that amino acid. PMID:2803251

Couée, I; Tipton, K F

1989-01-01

13

Reductive amination by recombinant Escherichia coli: whole cell biotransformation of 2-keto-3-methylvalerate to L-isoleucine.  

PubMed

A whole cell biotransformation system for reductive amination has been studied in recombinant Escherichia coli cells. Reductive amination of 2-keto-3-methylvalerate to L-isoleucine by a two-enzyme-cascade was achieved by overproduction of endogenous L-alanine dependent transaminase AvtA and heterologous L-alanine dehydrogenase from Bacillus subtilis in recombinant E. coli. Up to 100 mM L-isoleucine were produced from 100 mM 2-keto-3-methylvalerate and 100 mM ammonium sulfate. Regeneration of NADH as cofactor in the whole cell system was driven by glucose catabolism. The effects of defined gene deletions in the central carbon metabolism on biotransformation were tested. Strains lacking the NuoG subunit of NADH:ubiquinone oxidoreductase (complex I) or aceA encoding the glyoxylate cycle enzyme isocitrate lyase exhibited increased biotransformation rates. PMID:23831557

Lorenz, Elisabeth; Klatte, Stephanie; Wendisch, Volker F

2013-11-01

14

Effect of L-Valine on the growth and characterization of Sodium Acid Phthalate (SAP) single crystals  

NASA Astrophysics Data System (ADS)

Undoped and amino acid doped good quality single crystals of Sodium Acid Phthalate crystals (SAP) were grown by slow evaporation solution growth technique which are semiorganic in nature. The effect of amino acid (L-Valine) dopant on the growth and the properties of SAP single crystal was investigated. The single crystal X-ray diffraction studies and FT-IR studies were carried out to identify the crystal structure and the presence of functional groups in undoped and L-Valine doped SAP crystals. The transparent nature of the grown crystal was observed using UV-Visible spectrum. The thermal decomposition of the doped SAP crystals was investigated by thermo gravimetric analysis (TGA) and differential thermal analysis (DTA). The enhancement in the NLO property of the undoped and L-Valine doped SAP crystals using KDP crystal as a reference was studied using SHG measurements. Vickers micro hardness measurements are used for the study of mechanical strength of the grown crystals.

Nirmala, L. Ruby; Prakash, J. Thomas Joseph

2013-06-01

15

Possibility of wound dressing using poly(L-leucine)/poly(ethylene glycol)/poly(L-leucine) triblock copolymer.  

PubMed

ABA-type block copolymers (abbreviated as LEL) composed of poly(L-leucine) (PLL) as the A component and poly(ethylene glycol) (PEG) as the B component were synthesized by ring-opening polymerization of L-leucine N-carboxyanhydride initiated by primary amino group located at both ends of PEG chain. A silver sulfadiazine (AgSD)-impregnated wound dressing of sponge type was prepared by the lyophilization method. Morphological structure of this wound dressing by scanning electron microscopy was observed to be composed of a dense skin layer and a porous inner layer. Equilibrium water content of LEL wound dressing increased with an increase in PEG content in the block copolymer due to the hydrophilicity of PEG. AgSD release from AgSD-impregnated wound dressing in PBS buffer (pH = 7.4) was dependent on PEG content in the block copolymer. Release of AgSD was increased in proportion to the PEG content in the copolymer. Antibacterial capacity of AgSD-impregnated wound dressing was examined in agar plate against Pseudomonas aeruginosa and Staphylococcus aureus. It was found that the suppression of bacterial proliferation in the wound dressing was dependent upon the PEG content. In cytotoxicity test, cell damage did not occur by the release of AgSD from the LEL sponge matrix of AgSD-medicated wound dressing. In in vivo test, granulous tissue formation and wound contraction for the AgSD- and dehydroepiandrosterone-impregnated LEL-2 wound dressing were faster than for any other groups. PMID:10632395

Kim, H J; Choi, E Y; Oh, J S; Lee, H C; Park, S S; Cho, C S

2000-01-01

16

Study on optical properties of l-valine doped ADP crystal.  

PubMed

Single crystal of l-valine doped ammonium dihydrogen phosphate has been grown by slow evaporation method at room temperature. The crystalline nature of the grown crystal was confirmed using powder X-ray diffraction technique. The different functional groups of the grown crystal were identified using Fourier transform infrared analysis. The UV-visible studies were employed to examine the high optical transparency and influential optical constants for tailoring materials suitability for optoelectronics applications. The cutoff wavelength of the title crystal was found to be 280nm with wide optical band gap of 4.7eV. The dielectric measurements were carried to determine the dielectric constant and dielectric loss at room temperature. The grown crystal has been characterized by thermogravimetric analysis. The second harmonic generation efficiency of the grown crystal was determined by the classical Kurtz powder technique and it is found to be 1.92 times that of potassium dihydrogen phosphate. The grown crystal was identified as third order nonlinear optical material employing Z-scan technique using He-Ne laser operating at 632.8nm. PMID:25456665

Shaikh, R N; Anis, Mohd; Shirsat, M D; Hussaini, S S

2014-10-20

17

Study on optical properties of L-valine doped ADP crystal  

NASA Astrophysics Data System (ADS)

Single crystal of L-valine doped ammonium dihydrogen phosphate has been grown by slow evaporation method at room temperature. The crystalline nature of the grown crystal was confirmed using powder X-ray diffraction technique. The different functional groups of the grown crystal were identified using Fourier transform infrared analysis. The UV-visible studies were employed to examine the high optical transparency and influential optical constants for tailoring materials suitability for optoelectronics applications. The cutoff wavelength of the title crystal was found to be 280 nm with wide optical band gap of 4.7 eV. The dielectric measurements were carried to determine the dielectric constant and dielectric loss at room temperature. The grown crystal has been characterized by thermogravimetric analysis. The second harmonic generation efficiency of the grown crystal was determined by the classical Kurtz powder technique and it is found to be 1.92 times that of potassium dihydrogen phosphate. The grown crystal was identified as third order nonlinear optical material employing Z-scan technique using He-Ne laser operating at 632.8 nm.

Shaikh, R. N.; Anis, Mohd.; Shirsat, M. D.; Hussaini, S. S.

2015-02-01

18

Isolation and characterization of awamori yeast mutants with l-leucine accumulation that overproduce isoamyl alcohol.  

PubMed

Awamori shochu is a traditional distilled alcoholic beverage made from steamed rice in Okinawa, Japan. Although it has a unique aroma that is distinguishable from that of other types of shochu, no studies have been reported on the breeding of awamori yeasts. In yeast, isoamyl alcohol (i-AmOH), known as the key flavor of bread, is mainly produced from ?-ketoisocaproate in the pathway of l-leucine biosynthesis, which is regulated by end-product inhibition of ?-isopropylmalate synthase (IPMS). Here, we isolated mutants resistant to the l-leucine analog 5,5,5-trifluoro-dl-leucine (TFL) derived from diploid awamori yeast of Saccharomyces cerevisiae. Some of the mutants accumulated a greater amount of intracellular l-leucine, and among them, one mutant overproduced i-AmOH in awamori brewing. This mutant carried an allele of the LEU4 gene encoding the Ser542Phe/Ala551Val variant IPMS, which is less sensitive to feedback inhibition by l-leucine. Interestingly, we found that either of the constituent mutations (LEU4(S542F) and LEU4(A551V)) resulted in the TFL tolerance of yeast cells and desensitization to l-leucine feedback inhibition of IPMS, leading to intracellular l-leucine accumulation. Homology modeling also suggested that l-leucine binding was drastically inhibited in the Ser542Phe, Ala551Val, and Ser542Phe/Ala551Val variants due to steric hindrance in the cavity of IPMS. As we expected, awamori yeast cells expressing LEU4(S542F), LEU4(A551V), and LEU4(S542F/A551V) showed a prominent increase in extracellular i-AmOH production, compared with that of cells carrying the vector only. The approach described here could be a practical method for the breeding of novel awamori yeasts to expand the diversity of awamori taste and flavor. PMID:25060730

Takagi, Hiroshi; Hashida, Keisuke; Watanabe, Daisuke; Nasuno, Ryo; Ohashi, Masataka; Iha, Tomoya; Nezuo, Maiko; Tsukahara, Masatoshi

2015-02-01

19

3H-L-leucine transport by the promiscuous crustacean dipeptide-like cotransporter.  

PubMed

The crustacean intestine and hepatopancreas display a variety of solute transport mechanisms for transmembrane transfer of dietary contents from lumen to epithelial cytosol. An in vitro intestinal perfusion apparatus was used to characterize mucosal to serosoal (MS) and serosal to mucosal (SM) Zn(2+) -dependent (3)H-L-leucine transport by the intestine of the American lobster, Homarus americanus. Transmural 20?µM MS (3)H-L-leucine fluxes across lobster intestine were a hyperbolic function of luminal zinc concentration (1-50?µM) following Michaelis-Menten kinetics (K(m) = 2.67 ± 0.74?µM; J(max) = 19.56 ± 2.22?pmol/cm(2) ×min). Transmural 20?µM SM (3)H-L-leucine fluxes were not affected by serosal zinc, resulting in a highly significant stimulation of net amino acid transfer to the blood by luminal metal. MS fluxes of 20?µM (3)H-L-leucine were also hyperbolic functions of luminal [Cu(2+)], [Mn(2+)], [Na(+)], and [H(+)]. MS flux of (3)H-L-leucine was a sigmoidal function of luminal [L-leucine] and was stimulated by the addition of 20?µM luminal zinc at both pH 7.0 and 5.5. A greater enhanced amino acid transport occurred at the lower pH 5.5. MS flux of 20?µM (3)H-L-leucine in the presence of 20?µM zinc was significantly inhibited by addition of 100?µM luminal glycylsarcosine, and MS flux of 20?µM (3)H-glycylsarcosine was inhibited by 100?µM L-leucine in the presence of 20?µM zinc. Results suggest that (3)H-L-leucine and metals form a complex (e.g., Leu-Zn-Leu] that may functionally mimic dipeptides and use a dipeptide-like transporter during MS fluxes as suggested for fish and mammals. PMID:21732547

Obi, I; Wells, A L; Ortega, P; Patel, D; Farah, L; Zanotto, F P; Ahearn, G A

2011-10-01

20

Pushing product formation to its limit: metabolic engineering of Corynebacterium glutamicum for L-leucine overproduction.  

PubMed

Using metabolic engineering, an efficient L-leucine production strain of Corynebacterium glutamicum was developed. In the wild type of C. glutamicum, the leuA-encoded 2-isopropylmalate synthase (IPMS) is inhibited by low L-leucine concentrations with a K(i) of 0.4 mM. We identified a feedback-resistant IMPS variant, which carries two amino acid exchanges (R529H, G532D). The corresponding leuA(fbr) gene devoid of the attenuator region and under control of a strong promoter was integrated in one, two or three copies into the genome and combined with additional genomic modifications aimed at increasing L-leucine production. These modifications involved (i) deletion of the gene encoding the repressor LtbR to increase expression of leuBCD, (ii) deletion of the gene encoding the transcriptional regulator IolR to increase glucose uptake, (iii) reduction of citrate synthase activity to increase precursor supply, and (iv) introduction of a gene encoding a feedback-resistant acetohydroxyacid synthase. The production performance of the resulting strains was characterized in bioreactor cultivations. Under fed-batch conditions, the best producer strain accumulated L-leucine to levels exceeding the solubility limit of about 24 g/l. The molar product yield was 0.30 mol L-leucine per mol glucose and the volumetric productivity was 4.3 mmol l?¹ h?¹. These values were obtained in a defined minimal medium with a prototrophic and plasmid-free strain, making this process highly interesting for industrial application. PMID:24333966

Vogt, Michael; Haas, Sabine; Klaffl, Simon; Polen, Tino; Eggeling, Lothar; van Ooyen, Jan; Bott, Michael

2014-03-01

21

A novel l -isoleucine metabolism in Bacillus thuringiensis generating (2 S ,3 R ,4 S )-4-hydroxyisoleucine, a potential insulinotropic and anti-obesity amino acid  

Microsoft Academic Search

4-Hydroxyisoleucine (HIL) found in fenugreek seeds has insulinotropic and anti-obesity effects and is expected to be a novel\\u000a orally active drug for insulin-independent diabetes. Here, we show that the newly isolated strain Bacillus thuringiensis 2e2 and the closely related strain B. thuringiensis ATCC 35646 operate a novel metabolic pathway for l-isoleucine (l-Ile) via HIL and 2-amino-3-methyl-4-ketopentanoic acid (AMKP). The HIL

Jun Ogawa; Tomohiro Kodera; Sergey V. Smirnov; Makoto Hibi; Natalia N. Samsonova; Ryoukichi Koyama; Hiroyuki Yamanaka; Junichi Mano; Takashi Kawashima; Kenzo Yokozeki; Sakayu Shimizu

2011-01-01

22

Nano spray-dried pyrazinamide-l-leucine dry powders, physical properties and feasibility used as dry powder aerosols.  

PubMed

Abstract Objective: The aim of this study was to investigate the effect of adding l-leucine and using an ethanolic solvent on the physicochemical properties and aerodynamic behavior of nano spray-dried pyrazinamide (PZA)-l-leucine powders. Materials and methods: A nano spray dryer was employed to prepare PZA-l-leucine powders. The physicochemical properties were evaluated using a scanning electron microscope (SEM), differential scanning calorimetry and X-ray diffraction. The Andersen cascade impactor was used to evaluate the in vitro aerosolization performance of the sprayed powders. Results and discussion: The incorporation of l-leucine at 10% improved the percentage fine particle fraction (%FPF) in all ethanolic solvent formulations by up to nearly twofold (20.0-23.4%) compared to the normal spray-dried PZA of (8.8-13.0%). Changes in the particle density and morphology were also observed. The dense solid particles of PZA were completely converted to bulk hollow particles with a thin shell by increasing the l-leucine content up to 50%. Higher ethanol concentration resulted in larger dimensions of the hollow particle but did not directly affect the aerosolization performance. The co-spray dried PZA with 20% l-leucine in a 10% ethanol feed solvent gave the best aerosolization performance (FPF?=?33.0%). Conclusions: The co-spray dried PZA with a suitable l-leucine content using a nano spray drying technique could be applied to formulate the PZA DPI. PMID:25331092

Kaewjan, Kanogwan; Srichana, Teerapol

2014-10-21

23

Mechanism of specific influence of L-Glutamic acid on the shape of L-Valine crystals  

NASA Astrophysics Data System (ADS)

The specific interaction between L-valine (L-Val) and L-glutamic acid (L-Glu) in the process of evaporative crystallization from an aqueous solution has been investigated. It was found that only 2.0% (wt/wt) of L-Glu against the total amount of L-Val was required to induce significant agglomeration of L-Val. Interestingly, the agglomeration was only induced under acidic conditions, suggesting that the electrostatic interaction was an effective factor for the agglomeration process. As well as the electrostatic interaction, the length of the amino acid side chain was identified as another important factor. In addition, we confirmed that the incorporation rate of L-Glu into L-Val crystals was different during the nucleation and crystal growth stages. Based on these results, a mechanism has been proposed for the interaction of L-Glu and L-Val during the agglomeration process.

Yoshiura, Hiromu; Nagano, Hiroshi; Hirasawa, Izumi

2013-01-01

24

l-Leucine Supplementation Worsens the Adiposity of Already Obese Rats by Promoting a Hypothalamic Pattern of Gene Expression that Favors Fat Accumulation  

PubMed Central

Several studies showed that l-leucine supplementation reduces adiposity when provided before the onset of obesity. We studied rats that were exposed to a high-fat diet (HFD) for 10 weeks before they started to receive l-leucine supplementation. Fat mass was increased in l-leucine-supplemented rats consuming the HFD. Accordingly, l-leucine produced a hypothalamic pattern of gene expression that favors fat accumulation. In conclusion, l-leucine supplementation worsened the adiposity of rats previously exposed to HFD possibly by central mechanisms. PMID:24699194

Zampieri, Thais T.; Torres-Leal, Francisco L.; Campaña, Amanda B.; Lima, Fabio B.; Donato, Jose

2014-01-01

25

l-Valine derived chiral N-sulfinamides as effective organocatalysts for the asymmetric hydrosilylation of N-alkyl and N-aryl protected ketimines.  

PubMed

l-Valine derived N-sulfinamides have been developed as efficient enantioselective Lewis basic organocatalysts for the asymmetric reduction of N-aryl and N-alkyl ketimines with trichlorosilane. Catalyst 3c afforded up to 99% yield and 96% ee in the reduction of N-alkyl ketimines and up to 98% yield and 98% ee in the reduction of N-aryl ketimines. PMID:25380100

Wang, Chao; Wu, Xinjun; Zhou, Li; Sun, Jian

2015-01-14

26

l-Leucine transport in human breast cancer cells (MCF7 and MDA-MB-231): kinetics, regulation by estrogen and molecular identity of the transporter  

Microsoft Academic Search

The transport of l-leucine by two human breast cancer cell lines has been examined. l-Leucine uptake by MDA-MB-231 and MCF-7 cells was via a BCH-sensitive, Na+-independent pathway. l-Leucine uptake by both cell lines was inhibited by l-alanine, d-leucine and to a lesser extent by l-lysine but not by l-proline. Estrogen (17?-estradiol) stimulated l-leucine uptake by MCF-7 but not by MDA-MB-231

D. B. Shennan; J. Thomson; I. F. Gow; M. T. Travers; M. C. Barber

2004-01-01

27

Supplementing L-leucine to a low-protein diet increases tissue protein synthesis in weanling pigs.  

PubMed

Recent work with young pigs shows that reducing dietary protein intake can improve gut function after weaning but results in inadequate provision of essential amino acids for muscle growth. Because acute administration of L-leucine stimulates protein synthesis in piglet muscle, the present study tested the hypothesis that supplementing L-leucine to a low-protein diet may maintain the activation of translation initiation factors and adequate protein synthesis in multiple organs of post-weaning pigs. Eighteen 21-day pigs (Duroc×Landrace×Yorkshire) were fed low-protein diets (16.9% crude protein) supplemented with 0, 0.27 or 0.55% L-leucine (total leucine contents in the diets being 1.34, 1.61 or 1.88%, respectively). At 35 days of age, protein synthesis was determined using the [2H] phenylalanine flooding-dose technique. Additionally, total and phosphorylated levels of mammalian target of rapamycin (mTOR), ribosomal protein S6 kinase 1 (S6K1), and eIF4E-binding protein-1 (4E-BP1) were measured in longissimus muscle and liver. Compared with the control group, dietary supplementation with 0.55% L-leucine for 2 weeks increased (P<0.05): (1) the phosphorylated levels of S6K1 and 4E-BP1; (2) protein synthesis in skeletal muscle, liver, the heart, kidney, pancreas, spleen, and stomach; and (3) daily weight gain by 61%. Dietary supplementation with 0.27% L-leucine enhanced (P<0.05) protein synthesis in proximal small intestine, kidney and pancreas. These novel findings provide a molecular basis for designing effective nutritional means to increase the efficiency of nutrient utilization for protein accretion in neonates. PMID:20473536

Yin, Yulong; Yao, Kang; Liu, Zhaojin; Gong, Min; Ruan, Zheng; Deng, Dun; Tan, Bie; Liu, Zhiqiang; Wu, Guoyao

2010-11-01

28

Platform Engineering of Corynebacterium glutamicum with Reduced Pyruvate Dehydrogenase Complex Activity for Improved Production of l-Lysine, l-Valine, and 2-Ketoisovalerate  

PubMed Central

Exchange of the native Corynebacterium glutamicum promoter of the aceE gene, encoding the E1p subunit of the pyruvate dehydrogenase complex (PDHC), with mutated dapA promoter variants led to a series of C. glutamicum strains with gradually reduced growth rates and PDHC activities. Upon overexpression of the l-valine biosynthetic genes ilvBNCE, all strains produced l-valine. Among these strains, C. glutamicum aceE A16 (pJC4 ilvBNCE) showed the highest biomass and product yields, and thus it was further improved by additional deletion of the pqo and ppc genes, encoding pyruvate:quinone oxidoreductase and phosphoenolpyruvate carboxylase, respectively. In fed-batch fermentations at high cell densities, C. glutamicum aceE A16 ?pqo ?ppc (pJC4 ilvBNCE) produced up to 738 mM (i.e., 86.5 g/liter) l-valine with an overall yield (YP/S) of 0.36 mol per mol of glucose and a volumetric productivity (QP) of 13.6 mM per h [1.6 g/(liter × h)]. Additional inactivation of the transaminase B gene (ilvE) and overexpression of ilvBNCD instead of ilvBNCE transformed the l-valine-producing strain into a 2-ketoisovalerate producer, excreting up to 303 mM (35 g/liter) 2-ketoisovalerate with a YP/S of 0.24 mol per mol of glucose and a QP of 6.9 mM per h [0.8 g/(liter × h)]. The replacement of the aceE promoter by the dapA-A16 promoter in the two C. glutamicum l-lysine producers DM1800 and DM1933 improved the production by 100% and 44%, respectively. These results demonstrate that C. glutamicum strains with reduced PDHC activity are an excellent platform for the production of pyruvate-derived products. PMID:23835179

Buchholz, Jens; Schwentner, Andreas; Brunnenkan, Britta; Gabris, Christina; Grimm, Simon; Gerstmeir, Robert; Takors, Ralf; Eikmanns, Bernhard J.

2013-01-01

29

l-leucine partially rescues translational and developmental defects associated with zebrafish models of Cornelia de Lange syndrome.  

PubMed

Cohesinopathies are human genetic disorders that include Cornelia de Lange syndrome (CdLS) and Roberts syndrome (RBS) and are characterized by defects in limb and craniofacial development as well as mental retardation. The developmental phenotypes of CdLS and other cohesinopathies suggest that mutations in the structure and regulation of the cohesin complex during embryogenesis interfere with gene regulation. In a previous project, we showed that RBS was associated with highly fragmented nucleoli and defects in both ribosome biogenesis and protein translation. l-leucine stimulation of the mTOR pathway partially rescued translation in human RBS cells and development in zebrafish models of RBS. In this study, we investigate protein translation in zebrafish models of CdLS. Our results show that phosphorylation of RPS6 as well as 4E-binding protein 1 (4EBP1) was reduced in nipbla/b, rad21 and smc3-morphant embryos, a pattern indicating reduced translation. Moreover, protein biosynthesis and rRNA production were decreased in the cohesin morphant embryo cells. l-leucine partly rescued protein synthesis and rRNA production in the cohesin morphants and partially restored phosphorylation of RPS6 and 4EBP1. Concomitantly, l-leucine treatment partially improved cohesinopathy embryo development including the formation of craniofacial cartilage. Interestingly, we observed that alpha-ketoisocaproate (?-KIC), which is a keto derivative of leucine, also partially rescued the development of rad21 and nipbla/b morphants by boosting mTOR-dependent translation. In summary, our results suggest that cohesinopathies are caused in part by defective protein synthesis, and stimulation of the mTOR pathway through l-leucine or its metabolite ?-KIC can partially rescue development in zebrafish models for CdLS. PMID:25378554

Xu, Baoshan; Sowa, Nenja; Cardenas, Maria E; Gerton, Jennifer L

2014-11-01

30

L-Type Amino Acid Transporter 1-Mediated L-Leucine Transport at the Inner Blood-Retinal Barrier  

Microsoft Academic Search

PURPOSE. L-type amino acid transporters (LATs) prefer branched-chain and aromatic amino acids, including neuro- transmitter precursors. The objective of this study was to clarify the expression and function of LAT at the inner blood- retinal barrier (BRB). METHODS. (3H)L-Leucine transport at the inner BRB was char- acterized by using in vivo integration plot analysis and a con- ditionally immortalized rat

Masatoshi Tomi; Masahiko Mori; Masanori Tachikawa; Kazunori Katayama; Tetsuya Terasaki; Ken-ichi Hosoya

2005-01-01

31

Quantification of trimethylsilyl derivatives of amino acid disease biomarkers in neonatal blood samples by gas chromatography-mass spectrometry.  

PubMed

A novel analytical procedure was developed for the rapid determination of disease biomarkers of maple syrup urine disease (MSUD), L-valine, L-leucine, L-isoleucine, and L-phenylalanine in dried blood spots. Amino acids extracted from neonatal dried blood spots were rapidly derivatized with bis-(trimethylsilyl)trifluoroacetamide (BSTFA) and then analyzed by gas chromatography-mass spectrometry (GC-MS). Derivatization conditions and the method validation were studied: optimal derivatization conditions were acetonitrile as reaction solvent, a temperature of 100 degrees C, and a reaction time of 30 min. The proposed method provided a detection limit lower than 2.0 microM, recovery between 92% and 106%, and relative standard deviation less than 8.0%. The method was further tested in screening for neonatal MSUD by determination of L-valine, L-leucine, L-isoleucine, and L-phenylalanine in blood samples. The experimental results show that GC-MS following BSTFA derivatization is a rapid, simple, and sensitive method for the determination of amino acid disease biomarkers in blood samples, and is a potential tool for fast screening of MSUD. PMID:16385411

Shen, Xizhong; Deng, Chunhui; Wang, Ben; Dong, Ling

2006-02-01

32

A study of l-leucine, l-phenylalanine and l-alanine transport in the perfused rat mammary gland: possible involvement of LAT1 and LAT2  

Microsoft Academic Search

The transport of l-leucine, l-phenylalanine and l-alanine by the perfused lactating rat mammary gland has been examined using a rapid, paired-tracer dilution technique. The clearances of all three amino acids by the mammary gland consisted of a rising phase followed by a rapid fall-off, respectively, reflecting influx and efflux of the radiotracers. The peak clearance of l-leucine was inhibited by

D. B Shennan; D. T Calvert; M. T Travers; Y Kudo; C. A. R Boyd

2002-01-01

33

Thermal, Dielectric Studies on Pure and Amino Acid L-Glutamic Acid, L-Histidine L-Valine Doped Potassium Dihydrogen Phosphate Single Crystals  

NASA Astrophysics Data System (ADS)

Amino acids (L-Glutamic acid, L-Histidine, L-Valine) doped potassium dihydrogen phosphate crystals were grown by the solution growth technique. Slow cooling as well as slow evaporation methods were employed to grow these crystals. The concentration of dopants in the mother solution was varied from 0.1 mole % to 10 mole %. The solubility data for all dopant concentrations were determined. The variation in pH and the corresponding habit modification of the grown crystals were characterized with UV - VIS, FT-IR and SHG trace elements, and dielectric studies reveal slight distortion of lattice parameter for the heavily doped KDP crystals. TGA-DTA studies reveal good thermal stability. The dopants increase the hardness value of the material, which also depends on the concentration of the dopants. Amino acids doping improved the NLO properties. The detailed results on the spectral parameters, habit modifications and constant values will be presented.

Kumaresan, P.; Babu, S. Moorthy; Anbarasan, P. M.

34

Application of a Genetically Encoded Biosensor for Live Cell Imaging of L-Valine Production in Pyruvate Dehydrogenase Complex-Deficient Corynebacterium glutamicum Strains  

PubMed Central

The majority of biotechnologically relevant metabolites do not impart a conspicuous phenotype to the producing cell. Consequently, the analysis of microbial metabolite production is still dominated by bulk techniques, which may obscure significant variation at the single-cell level. In this study, we have applied the recently developed Lrp-biosensor for monitoring of amino acid production in single cells of gradually engineered L-valine producing Corynebacterium glutamicum strains based on the pyruvate dehydrogenase complex-deficient (PDHC) strain C. glutamicum ?aceE. Online monitoring of the sensor output (eYFP fluorescence) during batch cultivation proved the sensor's suitability for visualizing different production levels. In the following, we conducted live cell imaging studies on C. glutamicum sensor strains using microfluidic chip devices. As expected, the sensor output was higher in microcolonies of high-yield producers in comparison to the basic strain C. glutamicum ?aceE. Microfluidic cultivation in minimal medium revealed a typical Gaussian distribution of single cell fluorescence during the production phase. Remarkably, low amounts of complex nutrients completely changed the observed phenotypic pattern of all strains, resulting in a phenotypic split of the population. Whereas some cells stopped growing and initiated L-valine production, others continued to grow or showed a delayed transition to production. Depending on the cultivation conditions, a considerable fraction of non-fluorescent cells was observed, suggesting a loss of metabolic activity. These studies demonstrate that genetically encoded biosensors are a valuable tool for monitoring single cell productivity and to study the phenotypic pattern of microbial production strains. PMID:24465669

Mahr, Regina; Helfrich, Stefan; Nöh, Katharina; Blombach, Bastian; Kohlheyer, Dietrich; Frunzke, Julia

2014-01-01

35

Application of a genetically encoded biosensor for live cell imaging of L-valine production in pyruvate dehydrogenase complex-deficient Corynebacterium glutamicum strains.  

PubMed

The majority of biotechnologically relevant metabolites do not impart a conspicuous phenotype to the producing cell. Consequently, the analysis of microbial metabolite production is still dominated by bulk techniques, which may obscure significant variation at the single-cell level. In this study, we have applied the recently developed Lrp-biosensor for monitoring of amino acid production in single cells of gradually engineered L-valine producing Corynebacterium glutamicum strains based on the pyruvate dehydrogenase complex-deficient (PDHC) strain C. glutamicum ?aceE. Online monitoring of the sensor output (eYFP fluorescence) during batch cultivation proved the sensor's suitability for visualizing different production levels. In the following, we conducted live cell imaging studies on C. glutamicum sensor strains using microfluidic chip devices. As expected, the sensor output was higher in microcolonies of high-yield producers in comparison to the basic strain C. glutamicum ?aceE. Microfluidic cultivation in minimal medium revealed a typical Gaussian distribution of single cell fluorescence during the production phase. Remarkably, low amounts of complex nutrients completely changed the observed phenotypic pattern of all strains, resulting in a phenotypic split of the population. Whereas some cells stopped growing and initiated L-valine production, others continued to grow or showed a delayed transition to production. Depending on the cultivation conditions, a considerable fraction of non-fluorescent cells was observed, suggesting a loss of metabolic activity. These studies demonstrate that genetically encoded biosensors are a valuable tool for monitoring single cell productivity and to study the phenotypic pattern of microbial production strains. PMID:24465669

Mustafi, Nurije; Grünberger, Alexander; Mahr, Regina; Helfrich, Stefan; Nöh, Katharina; Blombach, Bastian; Kohlheyer, Dietrich; Frunzke, Julia

2014-01-01

36

Decreased pancreatic islet response to L-leucine in the spontaneously diabetic GK rat: enzymatic, metabolic and secretory data  

Microsoft Academic Search

\\u000a \\u000a Abstract\\u000a \\u000a   \\u000a \\u000a Aims\\/hypothesis. Pancreatic islets from hereditarily non-insulin-dependent diabetic Goto-Kakizaki (GK) rats have a deficient insulin response\\u000a not only to d-glucose but also to l-leucine. Our aim was to explain the cellular mechanism(s) underlying the beta-cell unresponsiveness to this amino acid. Methods. Freshly collagenase isolated islets from GK rats and healthy Wistar control rats matched with them for sex and

M.-H. Giroix; C. Saulnier; B. Portha

1999-01-01

37

Crystal Engineering of l-Alanine with l-Leucine Additive using Metal-Assisted and Microwave-Accelerated Evaporative Crystallization.  

PubMed

In this work, we demonstrated that the change in the morphology of l-alanine crystals can be controlled with the addition of l-leucine using the metal-assisted and microwave accelerated evaporative crystallization (MA-MAEC) technique. Crystallization experiments, where an increasing stoichiometric amount of l-leucine is added to initial l-alanine solutions, were carried out on circular poly(methyl methacrylate) (PMMA) disks modified with a 21-well capacity silicon isolator and silver nanoparticle films using microwave heating (MA-MAEC) and at room temperature (control experiments). The use of the MA-MAEC technique afforded for the growth of l-alanine crystals with different morphologies up to ?10-fold faster than those grown at room temperature. In addition, the length of l-alanine crystals was systematically increased from ?380 to ?2000 ?m using the MA-MAEC technique. Optical microscope images revealed that the shape of l-alanine crystals was changed from tetragonal shape (without l-leucine additive) to more elongated and wire-like structures with the addition of the l-leucine additive. Further characterization of l-alanine crystals was undertaken by Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy and powder X-ray diffraction (PXRD) measurements. In order to elucidate the growth mechanism of l-alanine crystals, theoretical simulations of l-alanine's morphology with and without l-leucine additive were carried out using Materials Studio software in conjunction with our experimental data. Theoretical simulations revealed that the growth of l-alanine's {011} and {120} crystal faces were inhibited due to the incorporation of l-leucine into these crystal faces in selected positions. PMID:24839404

Mojibola, Adeolu; Dongmo-Momo, Gilles; Mohammed, Muzaffer; Aslan, Kadir

2014-05-01

38

Thermal, dielectric studies on pure and amino acid ( L-glutamic acid, L-histidine, L-valine) doped KDP single crystals  

NASA Astrophysics Data System (ADS)

Amino acids ( L-glutamic acid, L-histidine, L-valine) doped potassium dihydrogen phospate crystals are grown by solution growth technique. Slow cooling as well as slow evaporation methods were employed to grow these crystals. The concentration of dopants in the mother solution was varied from 0.1 mol% to 10 mol%. The solubility data for all dopants concentration were determined. There is variation in pH value and hence, there is habit modification of the grown crystals were characterized with UV-VIS, FT-IR studies, SHG trace elements and dielectric studies reveal slight distortion of lattice parameter for the heavily doped KDP crystals. UV-Visible spectra confirm the improvement in the transparency of these crystals on doping metal ions. FT-IR spectra reveal strong absorption band between 1400 and 1600 cm -1 for metal ion doped crystals. TGA-DTA studies reveal good thermal stability. The dopants increase the hardness value of the material and it also depends on the concentration of the dopants. Amino acids doping improved the NLO properties. The detailed results on the spectral parameters, habit modifications and constant values will be presented.

Kumaresan, P.; Moorthy Babu, S.; Anbarasan, P. M.

2008-05-01

39

New poly(ester urea) derived from l-leucine: Electrospun scaffolds loaded with antibacterial drugs and enzymes.  

PubMed

Electrospun scaffolds from an amino acid containing poly(ester urea) (PEU) were developed as promising materials in the biomedical field and specifically in tissue engineering applications. The selected poly(ester urea) was obtained with a high yield and molecular weight by reaction of phosgene with a bis(?-aminoacyl)-?,?-diol-diester monomer. The polymer having l-leucine, 1,6-hexanediol and carbonic acid units had a semicrystalline character and relatively high glass transition and melting temperatures. Furthermore it was highly soluble in most organic solvents, an interesting feature that facilitated the electrospinning process and the effective incorporation of drugs with bactericidal activity (e.g. biguanide derivatives such as clorhexidine and polyhexamethylenebiguanide) and enzymes (e.g. ?-chymotrypsin) that accelerated the degradation process. Continuous micro/nanofibers were obtained under a wide range of processing conditions, being diameters of electrospun fibers dependent on the drug and solvent used. Poly(ester urea) samples were degradable in media containing lipases and proteinases but the degradation rate was highly dependent on the surface area, being specifically greater for scaffolds with respect to films. The high hydrophobicity of new scaffolds had repercussions on enzymatic degradability since different weight loss rates were found depending on how samples were exposed to the medium (e.g. forced or non-forced immersion). New scaffolds were biocompatible, as demonstrated by adhesion and proliferation assays performed with fibroblast and epithelial cells. PMID:25492010

Díaz, Angélica; Del Valle, Luis J; Tugushi, David; Katsarava, Ramaz; Puiggalí, Jordi

2015-01-01

40

Study of the Miscibility of Hard and Soft Segments of Optically Active Poly(amide-imide-ether-urethane) Copolymers based-L-Leucine with Different Soft Segments  

Microsoft Academic Search

Three series of new optically active poly(amide-imide-ether-urethane) (PAIEU) copolymers with different soft segments including polyethylene glycol (PEG), polypropylene glycol (PPG) or polytetramethylene glycol (PTMG) of molecular weight (MW) of 1000 were successfully synthesized. These copolymers were prepared via direct polycondensation reaction of an aromatic diacid based on L-leucine (1), 4,4’-methylene-bis-(4-phenylisocyanate) (MDI) (2) and different polyether polyols. FTIR spectroscopy shows the

Shadpour Mallakpour; Fatemeh Rafiemanzelat

2006-01-01

41

Involvement of LAT1 and LAT2 in the high- and low-affinity transport of L-leucine in human retinal pigment epithelial cells (ARPE-19 cells).  

PubMed

System L, which is encoded by LAT1 and LAT2, is an amino acid transport system that transports neutral amino acids, including several essential amino acids in an Na+-independent manner. Due to its broad substrate selectivity, system L has been proposed to mediate the transport of amino-acid-related drugs across the blood-tissue barriers. We characterized L-leucine transport and its corresponding transporter in a human retinal pigment epithelial cell line (ARPE-19 cells) as an in vitro model of the outer blood-retinal barrier. [3H]L-leucine uptake by ARPE-19 cells took place in an Na+-, Cl(-)-independent and saturable manner with K(m) values of 8.71 and 220 microM. This process was more potently cis-inhibited by substrates of LAT1 than those of LAT2. [3H]L-leucine efflux from ARPE-19 cells was trans-stimulated by substrates of LAT1 and LAT2 through the obligatory exchange mechanism of system L. Although RT-PCR analysis demonstrated that LAT1 and LAT2 mRNA are expressed in ARPE-19 cells, the LAT1 mRNA concentration is 42-fold higher than that of LAT2. Moreover, immunoblot analysis demonstrated that LAT1 is expressed in ARPE-19 cells. In conclusion, although the transport function of LAT1 is greater than that of LAT2, LAT1 and LAT2 are involved in L-leucine transport in ARPE-19 cells. PMID:19890975

Yamamoto, Atsushi; Akanuma, Shin-Ichi; Tachikawa, Masanori; Hosoya, Ken-Ichi

2010-05-01

42

Authentication of pure L-leucine products manufactured in China by discriminating between plant and animal sources using nitrogen stable isotope technique.  

PubMed

?L-leucine products among other branched chain amino acid supplements are highly susceptible to economically motivated adulteration. Curbing this menace is critical and timely. Hence, the ?(15) N composition of the L-leucine derived from plants and animals sources was estimated. The trophic enrichment phenomenon of ?(15) N composition was utilized to elucidate the sources. We finally established the distinction between the respective sources. Samples of plant sources (maize and soybean) and that of animal sources (pig fur and duck feather) were analyzed for ?(15) N isotopic signatures. An elemental analyzer which was connected to an isotope ratio mass spectrometer operated in the continuous flow mode was utilized. The raw materials were obtained from China. Statistical analysis was performed using descriptive statistics and one-way analysis of variance. The results indicated lower ?(15) N values of range -0.7344‰ to 2.384‰ and 1.032‰ to 2.064‰ for maize and soybean samples, respectively. Whereas, a range of 3.860‰ to 6.011‰ and 5.875‰ to 6.011‰ was, respectively, detected in pig fur and duck feather samples. The ?(15) N difference in plants and animals samples was significant (F = 165.0; P = 1.675 E-10 for maize and pig fur samples; F = 212.8; P = 0.0001284 for soybean and duck feather samples). It was observed that ?(15) N trophic enrichment is helpful in elucidating the respective sources. The authors can emphatically assert that the range of ?(15) N composition of L-leucine derived from plants sources within the study area is -1.000‰ to 3.000‰ whereas the range in animal sources is 4.000‰ to 9.000‰. Practical Application?This study provides a reliable approach in verifying the authenticity of not only L-leucine products but also other branched chain amino acid supplements and thereby would help in fraud detection of any economically motivated adulteration and mislabeling of these products. When coupled with H and O stable isotope techniques, the region-of-origin of the detected adulteration can also be traced successfully. It therefore serves as a guide to food regulatory bodies, food scientists, retailers of these products, consumers, and the general public at large. PMID:23458748

Huang, Jingyu; Nkrumah, Philip N; Appiah-Sefah, Gloria; Tang, Shijiang

2013-03-01

43

Intestinal absorption of D-galactose and L-leucine and intestinal disaccharidase activities in growing chickens fed different raw legume diets.  

PubMed

A significant (P less than .01) impairment in the rate of growth, along with a significant (P less than .01) inhibition in the rate of in vivo intestinal absorption of D-galactose and L-leucine, and in the in vitro intestinal absorption of D-galactose, was found in growing chickens fed ad libitum over a 60-day period, diets containing the raw legumes Vicia faba, Glycine soja, Vicia ervilia, and Phaseolus vulgaris as the main source of protein. Furthermore, a significant (P less than .01) reduction in the intestinal disaccharidase activity was found in the legume-fed chickens. The possible nature of these effects was discussed. PMID:7301750

Santidrian, S; Lasheras, B; Cenarruzabeitia, M N; Bolufer, J; Larralde, J

1981-04-01

44

Optimization of an effervescent tablet formulation using a central composite design optimization of an effervescent tablet formulation containing spray dried l-leucine and polyethylene glycol 6000 as lubricants using a central composite design  

Microsoft Academic Search

A rotatable central composite design is used to evaluate the effects of lubricants and compression force on the physical characteristics of effervescent tablets. Effervescent tablets lubricated with a combination of spray dried l-leucine and polyethylene glycol 6000 are prepared by direct compression and examined. Residual force, crushing strength and disintegration time are considered as response variables and related to the

Bärbel Rotthäuser; Gerolf Kraus; Peter C Schmidt

1998-01-01

45

A silver-sulfadiazine-impregnated synthetic wound dressing composed of poly-L-leucine spongy matrix: an evaluation of clinical cases.  

PubMed

The management of severe burns requires the suppression of bacterial growth, particularly when eschar and damaged tissue are present. For such cases, silver sulfadiazine (AgSD) cream has been traditionally applied. This antibacterial cream, however, cannot be used in conjunction with a temporary wound dressing that is needed to promote healing. The authors developed a synthetic wound dressing with drug delivery capability for clinical use by impregnating a poly-L-leucine spongy matrix with AgSD, which is released in a controlled, sustained fashion. In general, the dressing adhered firmly to the wound in the case of superficial second-degree burns, and during the healing process it separated spontaneously from the re-epithelialized surface. In the management of deep second-degree burns where eschar and damaged tissue were present, the dressing had to be changed at intervals of 3 to 5 days until it adhered firmly to the wound. Once the dressing had firmly attached to the wound, it was left in place until it separated spontaneously from the re-epithelialized surface. Dressing changes were fewer than with other treatments and the pain was effectively reduced. Cleansed wounds were effectively protected from bacterial contamination. Of 52 cases treated with this wound dressing, 93% (14/15) of superficial second-degree burns, 75% (3/4) of deep second-degree burns, 85% (6/7) of superficial and deep second-degree burns, and 75% (12/16) of split-thickness skin donor sites were evaluated as achieving good or excellent results. PMID:10147712

Kuroyanagi, Y; Kim, E; Kenmochi, M; Ui, K; Kageyama, H; Nakamura, M; Takeda, A; Shioya, N

1992-01-01

46

Folding and translocation of the undecamer of poly-L-leucine across the water-hexane interface. A molecular dynamics study  

NASA Technical Reports Server (NTRS)

The undecamer of poly-L-leucine at the water-hexane interface is studied by molecular dynamics simulations. This represents a simple model relevant to folding and insertion of hydrophobic peptides into membranes. The peptide, initially placed in a random coil conformation on the aqueous side of the system, rapidly translocates toward the hexane phase and undergoes interfacial folding into an alpha-helix in the subsequent 36 ns. Folding is nonsequential and highly dynamic. The initially formed helical segment at the N-terminus of the undecamer becomes transiently broken and, subsequently, reforms before the remainder of the peptide folds from the C-terminus. The formation of intramolecular hydrogen bonds during the folding of the peptide is preceded by a dehydration of the participating polar groups, as they become immersed in hexane. Folding proceeds through a short-lived intermediate, a 3(10)-helix, which rapidly interconverts to an alpha-helix. Both helices contribute to the equilibrium ensemble of folded structures. The helical peptide is largely buried in hexane, yet remains adsorbed at the interface. Its preferred orientation is parallel to the interface, although the perpendicular arrangement with the N-terminus immersed in hexane is only slightly less favorable. In contrast, the reversed orientation is highly unfavorable, because it would require dehydration of C-terminus carbonyl groups that do not participate in intramolecular hydrogen bonding. For the same reason, the transfer of the undecamer from the interface to the bulk hexane is also unfavorable. The results suggest that hydrophobic peptides fold in the interfacial region and, simultaneously, translocate into the nonpolar side of the interface. It is further implied that peptide insertion into the membrane is accomplished by rotating from the parallel to the perpendicular orientation, most likely in such a way that the N-terminus penetrates the bilayer.

Chipot, C.; Pohorille, A.

1998-01-01

47

Interactions in L-phenylalanine/L-leucine/L-glutamic Acid/L-proline + 2 M aqueous NaCl/2 M NaNO3 systems at different temperatures  

NASA Astrophysics Data System (ADS)

Density (?) and speed of sound ( u) in 2 M aqueous NaCl and 2 M NaNO3 solutions of amino acids: L-phenylalanine, L-leucine, L-glutamic acid, and L-proline have been measured for several molal concentrations of amino acids at different temperatures. The ? and u data have been used to calculate the values of isothermal compressibility and internal pressure at different temperatures. The trends of variations of ? T and P i with an increase in molal concentration of amino acid and temperature have been discussed in terms of solute-solvent and solute-solute interactions in the systems.

Riyazuddeen, Imran Khan; Afrin, Sadaf

2012-12-01

48

Synthesis and allosteric modulation of the dopamine receptor by peptide analogs of L-prolyl-L-leucyl-glycinamide (PLG) modified in the L-proline or L-proline and L-leucine scaffolds.  

PubMed

Novel analogs of L-prolyl-L-leucylglycinamide (PLG) were synthesized wherein the prolyl residue was replaced with other amino acids based on a 3,5-disubstituted proline scaffold. In some examples, the L-leucyl residue was also replaced by L-valine. These analogs were tested for their ability to enhance the binding of [(3)H]-N-propylnorapomorphine to short isoform of human dopamine D? receptors. Compounds 18b and 19b, increased [(3)H] NPA binding at concentrations between 10(-12) and 10(-9) M, which is similar to the effect of PLG in this assay and, provides evidences that these compounds are acting as allosteric modulators of dopamine D? receptors. PMID:24013414

Ferreira da Costa, Joana; Caamaño, Olga; Fernández, Franco; García-Mera, Xerardo; Sampaio-Dias, Ivo E; Brea, José Manuel; Cadavid, María Isabel

2013-11-01

49

Identification of N-{[6-chloro-4-(2,6-dimethoxyphenyl)quinazolin-2-yl]carbonyl}-l-leucine (NTRC-808), a novel nonpeptide chemotype selective for the neurotensin receptor type 2.  

PubMed

Compounds acting via the GPCR neurotensin receptor type 2 (NTS2) display analgesic effects in relevant animal models. Using a pharmacophore model based on known NT receptor nonpeptide compounds, we screened commercial databases to identify compounds that might possess activity at NTS2 receptor sites. Modification of our screening hit to include structural features known to be recognized by NTS1 and NTS2, led to the identification of the novel NTS2 selective nonpeptide, N-{[6-chloro-4-(2,6-dimethoxyphenyl)quinazolin-2-yl]carbonyl}-l-leucine (9). This compound is a potent partial agonist in the FLIPR assay with a profile of activity similar to that of the reference NTS2 analgesic nonpeptide levocabastine (5). PMID:25499438

Thomas, James B; Giddings, Angela M; Olepu, Srinivas; Wiethe, Robert W; Harris, Danni L; Narayanan, Sanju; Warner, Keith R; Sarret, Philippe; Longpre, Jean-Michel; Runyon, Scott P; Gilmour, Brian P

2015-01-15

50

Expanded target and cofactor repertoire for the transcriptional activator LysM from Sulfolobus.  

PubMed

Previously, Lrp-like transcriptional regulator LysM from the hyperthermoacidophilic crenarchaeon Sulfolobus solfataricus was proposed to have a single target, the lysWXJK operon of lysine biosynthesis, and a single effector molecule, l-lysine. Here we identify ?70 novel binding sites for LysM in the S. solfataricus genome with a LysM-specific nanobody-based chromatin immunoprecipitation assay coupled to microarray hybridization (ChIP-chip) and in silico target site prediction using an energy-based position weight matrix, and validate these findings with in vitro binding. LysM binds to intergenic and coding regions, including promoters of various amino acid biosynthesis and transport genes. We confirm that l-lysine is the most potent effector molecule that reduces, but does not completely abolish, LysM binding, and show that several other amino acids and derivatives, including d-lysine, l-arginine, l-homoarginine, l-glutamine and l-methionine and branched-chain amino acids l-leucine, l-isoleucine and l-valine, significantly affect DNA-binding properties of LysM. Therefore, it appears from this study that LysM is a much more versatile regulator than previously thought, and that it uses a variety of amino acids to sense nutritional quality of the environment and to modulate expression of the metabolic machinery of Sulfolobus accordingly. PMID:23355617

Song, Ningning; Nguyen Duc, Trong; van Oeffelen, Liesbeth; Muyldermans, Serge; Peeters, Eveline; Charlier, Daniel

2013-03-01

51

Current knowledge on isobutanol production with Escherichia coli, Bacillus subtilis and Corynebacterium glutamicum.  

PubMed

Due to steadily rising crude oil prices great efforts have been made to develop designer bugs for the fermentative production of higher alcohols, such as 2-methyl-1-butanol, 3-methyl-1-butanol and 2-Methyl-1-propanol (isobutanol), which all possess quality characteristics comparable to traditional oil based fuels. The common metabolic engineering approach uses the last two steps of the Ehrlich pathway, catalyzed by 2-ketoacid decarboxylase and an alcohol dehydrogenase converting the branched chain 2-ketoacids of L-isoleucine, L-leucine, and L-valine into the respective alcohols. This strategy was successfully used to engineer well suited and industrially employed bacteria, such as Escherichia coli, Bacillus subtilis and Corynebacterium glutamicum for the production of higher alcohols. Among these alcohols, isobutanol is currently the most promising one regarding final titer and yield. This article summarizes the current knowledge and achievements on isobutanol production with E. coli, B. subtilis and C. glutamicum regarding the metabolic engineering approaches and process conditions. PMID:22008938

Blombach, Bastian; Eikmanns, Bernhard J

2011-01-01

52

Behavioral responses of crayfish (Orconectes virilis andOrconectes rusticus) to chemical feeding stimulants.  

PubMed

We conducted two experiments to assess how chemical stimuli affect feeding behavior, grooming, and walking in the crayfishesOrconectes virilis andOrconectes rusticus. In the first experiment,O. virilis was tested with 29 amino acids; in the second experiment,0. rusticus was tested with 12 amino acids, 13 additional single compounds, and two six-compound mixtures. InO. virilis, the following amino acids, in order of potency, elicited feeding movements:L-isoleucine, glycine, hydroxy-L-proline,L-glutamate,L-valine, and B-alanine. Grooming increased in response toL-phenylalanine,L-tryptophan,L-tyrosine,L-leucine,L-methionine, and D-aspartate. InO. rusticus, both mixtures and the following single compounds, in order of potency, elicited feeding movements: cellobiose, sucrose, glycine, maltose, glycogen, nicotinic acid methyl ester, putrescine, andL-glutamate. Grooming increased in response to putrescine only, and walking increased in response to glycogen only. The responsiveness of these crayfishes to a wide variety of chemicals may reflect the omnivorous foraging habits of these crustaceans. PMID:24276999

Tierney, A J; Atema, J

1988-01-01

53

Far infrared spectra of solid state aliphatic amino acids in different protonation states.  

PubMed

Far infrared spectra of zwitterionic, cationic, and anionic forms of aliphatic amino acids in solid state have been studied experimentally. Measurements were done on glycine, L-alanine, L-valine, L-leucine, and L-isoleucine powder samples and film samples obtained from dried solutions prepared at pH ranging from 1 to 13. Solid state density functional theory calculations were also performed, and detailed potential energy distributions were obtained from normal mode results. A good correspondence between experimental and simulated spectra was achieved and this allowed us to propose an almost complete band assignment for the far infrared spectra of zwitterionic forms. In the 700-50 cm(-1) range, three regions were identified, each corresponding to a characteristic set of normal modes. A first region between 700 and 450 cm(-1) mainly contained the carboxylate bending, rocking, and wagging modes as well as the ammonium torsional mode. The 450-250 cm(-1) region was representative of backbone and sidechain skeletal bending modes. At last, the low wavenumber zone, below 250 cm(-1), was characteristic of carboxylate and skeletal torsional modes and of lattice modes. Assignments are also proposed for glycine cationic and anionic forms, but could not be obtained for all aliphatic amino acids due to the lack of structural data. This work is intended to provide fundamental information for the understanding of peptides vibrational properties. PMID:20331320

Trivella, Aurélien; Gaillard, Thomas; Stote, Roland H; Hellwig, Petra

2010-03-21

54

Two-metal ion mechanism of bovine lens leucine aminopeptidase: active site solvent structure and binding mode of L-leucinal, a gem-diolate transition state analogue, by X-ray crystallography.  

PubMed

The three-dimensional structures of bovine lens leucine aminopeptidase (blLAP) complexed with L-leucinal and of the unliganded enzyme have been determined at crystallographic resolutions of 1.9 and 1.6 A, respectively. Leucinal binds as a hydrated gem-diol to the active site of b1LAP), resembling the presumed gem-diolated intermediate in the catalytic pathway. One hydroxyl group bridges the two active site metal ions, and the other OH group is coordinated to Zn1. The high-resolution structure of the unliganded enzyme reveals one metal-bound water ligand, which is bridging both zinc ions. Together, these structures support a mechanism in which the bridging water ligand is the attacking hydroxide ion nucleophile. The gem-diolate intermediate is probably stabilized by four coordinating bonds to the dizinc center and by interaction with Lys-262 and Arg-336. In the mechanism, Lys-262 polarizes the peptide carbonyl group, which is also coordinated to Zn1. The Arg-336 side chain interacts with the substrate and the gem-diolate intermediate via water molecules. Near Arg-336 in the b1LAP-leucinal structure, an unusually short hydrogen bond is found between two active site water molecules. PMID:7578088

Sträter, N; Lipscomb, W N

1995-11-14

55

Trapping Phyllophaga spp. (Coleoptera: Scarabaeidae: Melolonthinae) in the United States and Canada using sex attractants.  

PubMed Central

The sex pheromone of the scarab beetle, Phyllophaga anxia, is a blend of the methyl esters of two amino acids, L-valine and L-isoleucine. A field trapping study was conducted, deploying different blends of the two compounds at 59 locations in the United States and Canada. More than 57,000 males of 61 Phyllophaga species (Coleoptera: Scarabaeidae: Melolonthinae) were captured and identified. Three major findings included: (1) widespread use of the two compounds [of the 147 Phyllophaga (sensu stricto) species found in the United States and Canada, males of nearly 40% were captured]; (2) in most species intraspecific male response to the pheromone blends was stable between years and over geography; and (3) an unusual pheromone polymorphism was described from P. anxia. Populations at some locations were captured with L-valine methyl ester alone, whereas populations at other locations were captured with L-isoleucine methyl ester alone. At additional locations, the L-valine methyl ester-responding populations and the L-isoleucine methyl ester-responding populations were both present, producing a bimodal capture curve. In southeastern Massachusetts and in Rhode Island, in the United States, P. anxia males were captured with blends of L-valine methyl ester and L-isoleucine methyl ester. PMID:19537965

Robbins, Paul S.; Alm, Steven R.; Armstrong, Charles. D.; Averill, Anne L.; Baker, Thomas C.; Bauernfiend, Robert J.; Baxendale, Frederick P.; Braman, S. Kris; Brandenburg, Rick L.; Cash, Daniel B.; Couch, Gary J.; Cowles, Richard S.; Crocker, Robert L.; DeLamar, Zandra D.; Dittl, Timothy G.; Fitzpatrick, Sheila M.; Flanders, Kathy L.; Forgatsch, Tom; Gibb, Timothy J.; Gill, Bruce D.; Gilrein, Daniel O.; Gorsuch, Clyde S.; Hammond, Abner M.; Hastings, Patricia D.; Held, David W.; Heller, Paul R.; Hiskes, Rose T.; Holliman, James L.; Hudson, William G.; Klein, Michael G.; Krischik, Vera L.; Lee, David J.; Linn, Charles E.; Luce, Nancy J.; MacKenzie, Kenna E.; Mannion, Catherine M.; Polavarapu, Sridhar; Potter, Daniel A.; Roelofs, Wendell L.; Royals, Brian M.; Salsbury, Glenn A.; Schiff, Nathan M.; Shetlar, David J.; Skinner, Margaret; Sparks, Beverly L.; Sutschek, Jessica A.; Sutschek, Timothy P.; Swier, Stanley R.; Sylvia, Martha M.; Vickers, Neil J.; Vittum, Patricia J.; Weidman, Richard; Weber, Donald C.; Williamson, R. Chris; Villani, Michael G

2006-01-01

56

Ruthenium-Nitrosyl Complexes with Glycine, l-Alanine, l-Valine, l-Proline, d-Proline, l-Serine, l-Threonine, and l-Tyrosine: Synthesis, X-ray Diffraction Structures, Spectroscopic and Electrochemical Properties, and Antiproliferative Activity  

PubMed Central

The reactions of [Ru(NO)Cl5]2– with glycine (Gly), l-alanine (l-Ala), l-valine (l-Val), l-proline (l-Pro), d-proline (d-Pro), l-serine (l-Ser), l-threonine (l-Thr), and l-tyrosine (l-Tyr) in n-butanol or n-propanol afforded eight new complexes (1–8) of the general formula [RuCl3(AA–H)(NO)]?, where AA = Gly, l-Ala, l-Val, l-Pro, d-Pro, l-Ser, l-Thr, and l-Tyr, respectively. The compounds were characterized by elemental analysis, electrospray ionization mass spectrometry (ESI-MS), 1H NMR, UV–visible and ATR IR spectroscopy, cyclic voltammetry, and X-ray crystallography. X-ray crystallography studies have revealed that in all cases the same isomer type (from three theoretically possible) was isolated, namely mer(Cl),trans(NO,O)-[RuCl3(AA–H)(NO)], as was also recently reported for osmium analogues with Gly, l-Pro, and d-Pro (see Z. Anorg. Allg. Chem.2013, 639, 1590–1597). Compounds 1, 4, 5, and 8 were investigated by ESI-MS with regard to their stability in aqueous solution and reactivity toward sodium ascorbate. In addition, cell culture experiments in three human cancer cell lines, namely, A549 (nonsmall cell lung carcinoma), CH1 (ovarian carcinoma), and SW480 (colon carcinoma), were performed, and the results are discussed in conjunction with the lipophilicity of compounds. PMID:24555845

2014-01-01

57

Branched-chain and aromatic amino acid catabolism into aroma volatiles in Cucumis melo L. fruit  

PubMed Central

The unique aroma of melons (Cucumis melo L., Cucurbitaceae) is composed of many volatile compounds biosynthetically derived from fatty acids, carotenoids, amino acids, and terpenes. Although amino acids are known precursors of aroma compounds in the plant kingdom, the initial steps in the catabolism of amino acids into aroma volatiles have received little attention. Incubation of melon fruit cubes with amino acids and ?-keto acids led to the enhanced formation of aroma compounds bearing the side chain of the exogenous amino or keto acid supplied. Moreover, L-[13C6]phenylalanine was also incorporated into aromatic volatile compounds. Amino acid transaminase activities extracted from the flesh of mature melon fruits converted L-isoleucine, L-leucine, L-valine, L-methionine, or L-phenylalanine into their respective ?-keto acids, utilizing ?-ketoglutarate as the amine acceptor. Two novel genes were isolated and characterized (CmArAT1 and CmBCAT1) encoding 45.6?kDa and 42.7?kDa proteins, respectively, that displayed aromatic and branched-chain amino acid transaminase activities, respectively, when expressed in Escherichia coli. The expression of CmBCAT1 and CmArAT1 was low in vegetative tissues, but increased in flesh and rind tissues during fruit ripening. In addition, ripe fruits of climacteric aromatic cultivars generally showed high expression of CmBCAT1 and CmArAT1 in contrast to non-climacteric non-aromatic fruits. The results presented here indicate that in melon fruit tissues, the catabolism of amino acids into aroma volatiles can initiate through a transamination mechanism, rather than decarboxylation or direct aldehyde synthesis, as has been demonstrated in other plants. PMID:20065117

Gonda, Itay; Bar, Einat; Portnoy, Vitaly; Lev, Shery; Burger, Joseph; Schaffer, Arthur A.; Tadmor, Ya'akov; Gepstein, Shimon; Giovannoni, James J.; Katzir, Nurit; Lewinsohn, Efraim

2010-01-01

58

Essential Amino Acid Methyl Esters: Major Sex Pheromone Components of the Cranberry White Grub, Phyllophaga anxia (Coleoptera: Scarabaeidae)  

Microsoft Academic Search

Chiral capillary gas chromatographic–electroantennographic detection (GC-EAD) analysis indicates that L-valine and L-isoleucine methyl esters are the major sex pheromone components released by females of the cranberry white grub, Phyllophaga anxia (LeConte). The GC retention times and GC-mass spectrometry of the two natural compounds were identical to those of authentic standards. Of five reproducible GC-EAD active components revealed with female volatiles,

Aijun Zhang; Paul S. Robbins; Walter S. Leal; Michael G. Villani; Wendell L. Roelofs

1997-01-01

59

Biosynthesis of Kitasamycin(Leucomycin) by Leucine Analog-Resistant Mutants of Streptomyces kitasatoensis  

PubMed Central

The biosynthesis of kitasamycin in Streptomyces kitasatoensis B-896 was profoundly influenced by the addition of precursors to complex and defined media: l-valine and l-leucine directed biosynthesis towards the pairs A4/A5 (R2 = butyryl) and A1/A3 (R2 = isovaleryl), respectively, and total kitasamycin titers were doubled and quadrupled, respectively. S. kitasatoensis B-896 was very resistant (>20 mg/ml) to ?-aminobutyric acid, an analog of l-valine, but very susceptible to l-leucine analogs 5?, 5?, 5?-trifluoroleucine and 4-azaleucine (5 to 10 ?g/ml). The inhibition by 4-azaleucine could be reversed by l-leucine, but by none of the other amino acids of the pyruvate family or the amino acids of the aspartate pathway. 4-Azaleucine-resistant mutants were isolated which in the absence of any precursors overproduced l-leucine and a kitasamycin complex mainly consisting of the pair A1/A3. These 4-azaleucine-resistant mutants are presumed to be regulatory mutants in which ?-isopropylmalate synthase, the first enzyme of the l-leucine pathway, has become either derepressed or desensitized to leucine feedback inhibition. l-Leucine-regulatory mutants have economic value: in the absence of expensive precursors, they produce a kitasamycin complex in which the most potent pair A1/A3 is dominant and the least active components are absent. Images PMID:525992

Vézina, Claude; Bolduc, Cécile; Kudelsk, Alicia; Audet, Pierre

1979-01-01

60

Emission of methylbutyric acid from Gypsophila paniculata L. during bud opening: Changes in amino acid catabolism  

Microsoft Academic Search

To elucidate the mechanism of methylbutyric acid emission which is responsible for the unpleasant odor of gypsophila inflorescences (Gypsophila paniculata L. ‘Bristol Fairy’ and ‘Golan’), we investigated the activities of enzymes in the catabolic pathway of branched-chain amino acids. The continuous application of either 10mM l-leucine, 10mM l-isoleucine or 4.5mM isovaleraldehyde increased the production of methylbutyric acids. When gypsophila inflorescences

Hataitip Nimitkeatkai; Yoshinori Ueda; Hajime Furukawa; Katsuhiko Inamoto; Motoaki Doi

2005-01-01

61

Characterization and modification of enzymes in the 2-ketoisovalerate biosynthesis pathway of Ralstonia eutropha H16.  

PubMed

2-Ketoisovalerate is an important cellular intermediate for the synthesis of branched-chain amino acids as well as other important molecules, such as pantothenate, coenzyme A, and glucosinolate. This ketoacid can also serve as a precursor molecule for the production of biofuels, pharmaceutical agents, and flavor agents in engineered organisms, such as the betaproteobacterium Ralstonia eutropha. The biosynthesis of 2-ketoisovalerate from pyruvate is carried out by three enzymes: acetohydroxyacid synthase (AHAS, encoded by ilvBH), acetohydroxyacid isomeroreductase (AHAIR, encoded by ilvC), and dihydroxyacid dehydratase (DHAD, encoded by ilvD). In this study, enzymatic activities and kinetic parameters were determined for each of the three R. eutropha enzymes as heterologously purified proteins. AHAS, which serves as a gatekeeper for the biosynthesis of all three branched-chain amino acids, demonstrated the tightest regulation through feedback inhibition by L-valine (IC50?=?1.2 mM), L-isoleucine (IC50?=?2.3 mM), and L-leucine (IC50?=?5.4 mM). Intermediates in the valine biosynthesis pathway also exhibit feedback inhibitory control of the AHAS enzyme. In addition, AHAS has a very weak affinity for pyruvate (KM?=?10.5 ?M) and is highly selective towards 2-ketobutyrate (R?=?140) as a second substrate. AHAIR and DHAD are also inhibited by the branched-chain amino acids, although to a lesser extent when compared to AHAS. Experimental evolution and rational site-directed mutagenesis revealed mutants of the regulatory subunit of AHAS (IlvH) (N11S, T34I, A36V, T104S, N11F, G14E, and N29H), which, when reconstituted with wild-type IlvB, lead to AHAS having reduced valine, leucine, and isoleucine sensitivity. The study of the kinetics and inhibition mechanisms of R. eutropha AHAS, AHAIR, and DHAD has shed light on interactions between these enzymes and the products they produce; it, therefore, can be used to engineer R. eutropha strains with optimal production of 2-ketoisovalerate for value-added materials. PMID:25081555

Lu, Jingnan; Brigham, Christopher J; Plassmeier, Jens K; Sinskey, Anthony J

2015-01-01

62

Polymeric sulfated amino acid surfactants: a class of versatile chiral selectors for micellar electrokinetic chromatography (MEKC) and MEKC-MS.  

PubMed

In this work, three amino acid-derived (l-leucinol, l-isoleucinol, l-valinol) sulfated chiral surfactants are synthesized and polymerized. These chiral sulfated surfactants are thoroughly characterized to determine critical micelle concentration, aggregation number, polarity, optical rotation, and partial specific volume. For the first time the morphological behavior of polymeric sulfated surfactants is revealed using cryogenic high-resolution electron microscopy. The polysodium N-undecenoyl-l-leucine sulfate shows distinct tubular structure, while polysodium N-undecenoyl-l-valine sulfate also shows tubular morphology but without any distinct order of the tubes. On the other hand, polysodium N-undecenoyl-l-isoleucine sulfate (poly-l-SUCILS) displays random distribution of coiled/curved filaments with heavy association of tightly and loosely bound water. All three polymeric sulfated surfactants are compared for enantioseparation of a broad range of structurally diverse racemic compounds at very acidic, neutral, and basic pH conditions in micellar electrokinetic chromatography (MEKC). A small combinatorial library of 10 structurally related phenylethylamines (PEAs) is investigated for chiral separation under acidic and moderately acidic to neutral pH conditions using an experimental design. In contrast to neutral pH conditions, at acidic pH, significantly enhanced chiral resolution is obtained for class I and class II PEAs due to the compact structure of polymeric sulfated surfactants. It is observed that the presence of a hydroxy group on the benzene ring of PEAs resulted in deterioration of enantioseparation. A sensitive MEKC-mass spectrometry (MS) method is developed for one of the PEAs (e.g., (+/-)-pseudoephedrine) in human urine. Very low limit of detection (LOD) is obtained at pH 2.0 (LOD 325 ng/mL), which is approximately 16 times better compared to pH 8.0 (LOD 5.2 microg/mL). Another broad range of chiral analytes (beta-blockers, phenoxypropionic acid, benzoin derivatives, PTH-amino acids, benzodiazepinones) studied also provided improved chiral separation at low pH compared to high-pH conditions. Among the three polymeric sulfated surfactants, poly-l-SUCILS with two chiral centers on the polymer head group provided overall higher enantioresolution for the investigated acidic, basic, and neutral compounds. This work clearly demonstrates for the first time the superiority of chiral separation and sensitive MS detection at low pH over conventional high-pH chiral separation and detection employing anionic chiral polymeric surfactants in MEKC and MEKC-MS. PMID:17263313

Rizvi, Syed Asad Ali; Zheng, Jie; Apkarian, Robert P; Dublin, Steven N; Shamsi, Shahab A

2007-02-01

63

Synthesis and biological evaluation of L-valine-amidoximeesters as double prodrugs of amidines.  

PubMed

In general, drugs containing amidines suffer from poor oral bioavailability and are often converted into amidoxime prodrugs to overcome low uptake from the gastrointestinal tract. The esterification of amidoximes with amino acids represents a newly developed double prodrug principle creating derivatives of amidines with both improved oral availability and water solubility. N-valoxybenzamidine (1) is a model compound for this principle, which has been transferred to the antiprotozoic drug pentamidine (8). Prodrug activation depends on esterases and mARC and is thus independent from activation by P450 enzymes. Therefore, drug-drug interactions or side effects will be minimized. The synthesis of these two compounds was established, and their biotransformation was studied in vitro and in vivo. Bioactivation of N-valoxybenzamidine (1) and N,N'-bis(valoxy)pentamidine (7) via hydrolysis and reduction has been demonstrated in vitro with porcine and human subcellular enzyme preparations and the mitochondrial Amidoxime Reducing Component (mARC). Moreover, activation of N-valoxybenzamidine (1) by porcine hepatocytes was studied. In vivo, the bioavailability in rats after oral application of N-valoxybenzamidine (1) was about 88%. Similarly, N,N'-bis(valoxy)pentamidine (7) showed oral bioavailability. Analysis of tissue samples revealed high concentrations of pentamidine (8) in liver and kidney. PMID:21345682

Kotthaus, Joscha; Hungeling, Helen; Reeh, Christiane; Kotthaus, Jürke; Schade, Dennis; Wein, Silvia; Wolffram, Siegfried; Clement, Bernd

2011-03-15

64

Synthesis and biological evaluation of l-valine-amidoximeesters as double prodrugs of amidines  

Microsoft Academic Search

In general, drugs containing amidines suffer from poor oral bioavailability and are often converted into amidoxime prodrugs to overcome low uptake from the gastrointestinal tract. The esterification of amidoximes with amino acids represents a newly developed double prodrug principle creating derivatives of amidines with both improved oral availability and water solubility. N-valoxybenzamidine (1) is a model compound for this principle,

Joscha Kotthaus; Helen Hungeling; Christiane Reeh; Jürke Kotthaus; Dennis Schade; Silvia Wein; Siegfried Wolffram; Bernd Clement

2011-01-01

65

Leucine dehydrogenase from Corynebacterium pseudodiphtheriticum: purification and characterization.  

PubMed

Leucine dehydrogenase [EC 1.4.1.9] was purified to homogeneity from Corynebacterium pseudodiphtheriticum ICR 2210. The enzyme consisted of a single polypeptide with a molecular weight of about 34,000. Stepwise Edman degradation provided the N-terminal sequence of the first 24 amino acids, and carboxypeptidase Y digestion provided the C-terminal sequence of the last 2 amino acids. Although the enzyme catalyzed the reversible deamination of various branched-chain L-amino acids, L-valine was the best substrate for oxidative deamination at pH 10.9 and the saturated concentration. The enzyme, however, had higher reactivity for L-leucine, and the kcat/Km value for L-leucine was higher than that for L-valine. The enzyme required NAD+ as a natural coenzyme. The NAD+ analogs 3-acetylpyridine-NAD+ and deamino-NAD+ were much better coenzymes than NAD+. The enzyme activity was significantly reduced by sulfhydryl reagents and pyridoxal 5'-phosphate. D-Enantiomers of the substrate amino acids competitively inhibited the oxidation of L-valine. PMID:1368565

Misono, H; Sugihara, K; Kuwamoto, Y; Nagata, S; Nagasaki, S

1990-06-01

66

Bioconversion of 2-amino acids to 2-hydroxy acids by Clostridium butyricum  

Microsoft Academic Search

Analysis by gas chromatography-mass spectrometry (GC-MS) of 24-h cultures of Clostridium butyricum type strain in synthetic BMG medium supplemented with various 2-amino acids (10 mM) revealed the presence of the corresponding 2-hydroxy acids. C. butyricum was able to bioconvert l-valine, dl-norvaline, l-leucine, dl-norleucine, l-methionine and l-phenylalanine as well as unusual 2-amino acids, i.e., l-2-aminobutyric acid, l-2-amino-4-pentenoic acid, dl-2-aminooctanoic acid, and

Nasser Khelifa; Annabelle Dugay; Annie-Claude Tessedre; François Guyon; Alain Rimbault

1998-01-01

67

Thermodynamic study of solvation of some amino acids, diglycine and lysozyme in aqueous and mixed aqueous solutions  

Microsoft Academic Search

Apparent molar adiabatic compressibilities and viscosities of glycine, dl-?-alanine, dl-?-amino-n-butyric acid, l-valine, l-leucine and diglycine have been determined in aqueous and mixed aqueous solutions of mB=1.0, 2.0, 3.0, 4.0 and 5.0 aqueous n-propanol solutions at 298.15K. From these data the partial molar adiabatic compressibilities and viscosity B-coefficients have been evaluated to calculate the corresponding transfer functions. The partial molar adiabatic

Tarlok S. Banipal; Gagandeep Singh

2004-01-01

68

Potential antiproteolytic effects of L-leucine: observations of in vitro and in vivo studies  

PubMed Central

The purpose of present review is to describe the effect of leucine supplementation on skeletal muscle proteolysis suppression in both in vivo and in vitro studies. Most studies, using in vitro methodology, incubated skeletal muscles with leucine with different doses and the results suggests that there is a dose-dependent effect. The same responses can be observed in in vivo studies. Importantly, the leucine effects on skeletal muscle protein synthesis are not always connected to the inhibition of skeletal muscle proteolysis. As a matter of fact, high doses of leucine incubation can promote suppression of muscle proteolysis without additional effects on protein synthesis, and low leucine doses improve skeletal muscle protein ynthesis but have no effect on skeletal muscle proteolysis. These research findings may have an important clinical relevancy, because muscle loss in atrophic states would be reversed by specific leucine supplementation doses. Additionally, it has been clearly demonstrated that leucine administration suppresses skeletal muscle proteolysis in various catabolic states. Thus, if protein metabolism changes during different atrophic conditions, it is not surprising that the leucine dose-effect relationship must also change, according to atrophy or pathological state and catabolism magnitude. In conclusion, leucine has a potential role on attenuate skeletal muscle proteolysis. Future studies will help to sharpen the leucine efficacy on skeletal muscle protein degradation during several atrophic states. PMID:18637185

Zanchi, Nelo E; Nicastro, Humberto; Lancha, Antonio H

2008-01-01

69

Synthesis and biological activity of novel thiourea derivatives as carbonic anhydrase inhibitors.  

PubMed

Abstract A new series of chiral thiourea derivatives (5a-5c) and thiourea containing benzimidazole moieties (9b-9e) were synthesized from different amino acids (l-valine, l-isoleucine, l-methionine, l-phenylalanine, and d-phenylglycine). The compounds were characterized and tested against the two most studied members of the pH regulatory enzyme family, carbonic anhydrase (CA, EC 4.2.1.1). KI values of the novel compounds were measured in the range of 3.4-73.6??M for hCA I isozyme and 8.7-1.44.2??M for hCA II isozyme, respectively. Phenol was also tested as standard in order to understand the structure activity relationship and the clinically used sulfonamide acetazolamide was tested for comparison reasons. All of the compounds exhibited competitive inhibition with 4-nitrophenylacetate as substrate. PMID:24666304

Korkmaz, Neslihan; Obaidi, Oday A; Senturk, Murat; Astley, Demet; Ekinci, Deniz; Supuran, Claudiu T

2015-02-01

70

Postnatal amino acid uptake by the rat small intestine. Changes in membrane transport systems for amino acids associated with maturation of jejunal morphology.  

PubMed

The uptake of a number of amino acids by the developing small intestine of the rat was investigated in vitro. L-valine, L-leucine, L-methionine, L-phenylalanine, L-arginine and L-lysine were all taken up by active transport and concentrated within the jejunal mucosa. GABA was not actively transported by the jejunum. The kinetics of carrier transport of amino acids was determined from birth to maturity. The Michaelis constant (Km) of the L-leucine, L-methionine, L-arginine and l-lysine transport systems was found to be low postnatally and increased with age, particularly after the time of weaning. The rate of l-leucine, L-methionine, L-phenylalanine and L-lysine transport (Vmax) was high postnatally but decreased after weaning. Neutral amino acids were transported at higher rates than basic amino acids. l-arginine was poorly transported by the jejunum. The specificity of transport systems for amino acids was investigated in inhibition studies. Amino acid transport systems appeared to be polyfunctional in the postnatal period but were more specific in post-weaned animals. The changes in kinetics and specificity of amino acid transport in the small intestine are discussed with reference to their possible functional significance and to the maturational changes in the jejunum, particularly with the appearance of a functionally distinct absorptive cell lining the intestinal villi during the third postnatal week (the time of weaning). PMID:121999

Murphy, S; Daniels, V G

1979-04-01

71

Intestinal nutrient absorption - A biomarker for deleterious heavy metals in aquatic environments  

SciTech Connect

The deleterious effects of heavy metals on absorptive processes at the membrane surface will be summarized. Among the deleterious heavy metal chlorides (HgCl{sub 2}, CH{sub 3}HgCl, CdCl{sub 2}, CoCl{sub 2}, SrCl{sub 2}) tested HgCl{sub 2}, CH{sub 3}HgCl, and CdCl{sub 2} inhibit the absorption of several amino acids and sugars (L-leucine, L-methionine, L-isoleucine, L-lysine, cyclolencine, D-glucose, and D-galactose). The dose dependent inhibition of L-leucine uptake by HgCl{sub 2} is shown in a number of fish from different collection sites representing nektonic plankton feeders as well as demersal carnivores. The same type of data is shown for both HgCl{sub 2} and HC{sub 3}HgCl in the case of the commercially important summer flounder. Since the overall rate of intestinal absorption of amino acids and sugars involves the three processes of simple diffusion, protein-mediated facilitated diffusions, and protein-mediated sodium dependent active transport, the inhibition of the overall rate may not be sensitive enough as a biomarker. However, the active component, which alone accumulates essential amino acids in the tissue, appears to be very sensitive and can be used as a biomarker. The terminal tissue-to-medium (T/M) ratio of L-leucine concentration shows a 2-3 fold accumulation in the absence of mercury. Since the diffusional components can at best equilibrate L-leucine across the membrane % inhibition of the active component can be calculated after subtracting 1 from the experimental T/M values. The resulting inhibition is very sever ranging from approximately 50-100% for HgCl{sub 2} and 20-70% for CH{sub 3}HgCl over a range of 5-20 ppm of mercury.

Farmanfarmaian, A. (Rutgers, The State Univ. of New Jersey, Piscataway (USA))

1988-09-01

72

Vibrational analysis of amino acids and short peptides in hydrated media. I. L-glycine and L-leucine.  

PubMed

Raman scattering and Fourier-transform infrared (FT-IR) attenuated transmission reflectance (ATR) spectra of two alpha-amino acids (alpha-AAs), i.e., glycine and leucine, were measured in H2O and D2O (at neutral pH and pD). This series of observed vibrational data gave us the opportunity to analyze vibrational features of both AAs in hydrated media by density functional theory (DFT) calculations at the B3LYP/6-31++G* level. Harmonic vibrational modes calculated after geometry optimization on the clusters containing each AA and 12 surrounding water molecules, which represent primary models for hydration scheme of amino acids, allowed us to assign the main observed peaks. PMID:17243664

Derbel, Najoua; Hernández, Belén; Pflüger, Fernando; Liquier, Jean; Geinguenaud, Frédéric; Jaïdane, Nejmeddine; Lakhdar, Zohra Ben; Ghomi, Mahmoud

2007-02-15

73

Gustatory responsiveness to the 20 proteinogenic amino acids in the spider monkey (Ateles geoffroyi).  

PubMed

The gustatory responsiveness of four adult spider monkeys to the 20 proteinogenic amino acids was assessed in two-bottle preference tests of brief duration (1min). We found that Ateles geoffroyi responded with significant preferences for seven amino acids (glycine, l-proline, l-alanine, l-serine, l-glutamic acid, l-aspartic acid, and l-lysine) when presented at a concentration of 100mM and/or 200mM and tested against water. At the same concentrations, the animals significantly rejected five amino acids (l-tryptophan, l-tyrosine, l-valine, l-cysteine, and l-isoleucine) and were indifferent to the remaining tastants. Further, the results show that the spider monkeys discriminated concentrations as low as 0.2mM l-lysine, 2mM l-glutamic acid, 10mM l-proline, 20mM l-valine, 40mM glycine, l-serine, and l-aspartic acid, and 80mM l-alanine from the alternative stimulus, with individual animals even scoring lower threshold values. A comparison between the taste qualities of the proteinogenic amino acids as described by humans and the preferences and aversions observed in the spider monkeys suggests a fairly high degree of agreement in the taste quality perception of these tastants between the two species. A comparison between the taste preference thresholds obtained with the spider monkeys and taste detection thresholds reported in human subjects suggests that the taste sensitivity of A. geoffroyi for the amino acids tested here might match that of Homo sapiens. The results support the assumption that the taste responses of spider monkeys to proteinogenic amino acids might reflect an evolutionary adaptation to their frugivorous and thus protein-poor diet. PMID:24480073

Larsson, Jenny; Maitz, Anna; Hernandez Salazar, Laura Teresa; Laska, Matthias

2014-03-29

74

Industrial production of amino acids by coryneform bacteria.  

PubMed

In the 1950s Corynebacterium glutamicum was found to be a very efficient producer of L-glutamic acid. Since this time biotechnological processes with bacteria of the species Corynebacterium developed to be among the most important in terms of tonnage and economical value. L-Glutamic acid and L-lysine are bulk products nowadays. L-Valine, L-isoleucine, L-threonine, L-aspartic acid and L-alanine are among other amino acids produced by Corynebacteria. Applications range from feed to food and pharmaceutical products. The growing market for amino acids produced with Corynebacteria led to significant improvements in bioprocess and downstream technology as well as in molecular biology. During the last decade big efforts were made to increase the productivity and to decrease the production costs. This review gives an overview of the world market for amino acids produced by Corynebacteria. Significant improvements in bioprocess technology, i.e. repeated fed batch or continuous production are summarised. Bioprocess technology itself was improved furthermore by application of more sophisticated feeding and automatisation strategies. Even though several amino acids developed towards commodities in the last decade, side aspects of the production process like sterility or detection of contaminants still have increasing relevance. Finally one focus of this review is on recent developments in downstream technology. PMID:12948636

Hermann, Thomas

2003-09-01

75

A serum metabolomic investigation on hepatocellular carcinoma patients by chemical derivatization followed by gas chromatography/mass spectrometry.  

PubMed

The purpose of this study was to investigate the serum metabolic difference between hepatocellular carcinoma (HCC, n = 20) male patients and normal male subjects (n = 20). Serum metabolome was detected through chemical derivatization followed by gas chromatography/mass spectrometry (GC/MS). The acquired GC/MS data was analyzed by stepwise discriminant analysis (SDA) and support vector machine (SVM). The metabolites including butanoic acid, ethanimidic acid, glycerol, L-isoleucine, L-valine, aminomalonic acid, D-erythrose, hexadecanoic acid, octadecanoic acid, and 9,12-octadecadienoic acid in combination with each other gave the strongest segregation between the two groups. By applying these variables, our method provided a diagnostic model that could well discriminate between HCC patients and normal subjects. More importantly, the error count estimate for each group was 0%. The total classifying accuracy of the discriminant function tested by SVM 20-fold cross validation was 75%. This technique is different from traditional ones and appears to be a useful tool in the area of HCC diagnosis. PMID:18767022

Xue, Ruyi; Lin, Zhenxin; Deng, Chunhui; Dong, Ling; Liu, Taotao; Wang, Jiyao; Shen, Xizhong

2008-10-01

76

Glutamate formation via the leucine-to-glutamate pathway of rat pancreas.  

PubMed

The leucine-to-glutamate (Leu?Glu) pathway, which metabolizes the carbon atoms of l-leucine to form l-glutamate, was studied by incubation of rat tissue segments with l-[U-(14)C]leucine and estimation of the [(14)C]glutamate formed. Metabolism of the leucine carbon chain occurs in most rat tissues, but maximal activity of the Leu?Glu pathway for glutamate formation is limited to the thoracic aorta and pancreas. In rat aorta, the Leu?Glu pathway functions to relax the underlying smooth muscle; its functions in the pancreas are unknown. This report characterizes the Leu?Glu pathway of rat pancreas and develops methods to examine its functions. Pancreatic segments effect net formation of glutamate on incubation with l-leucine, l-glutamine, or a mix of 18 other plasma amino acids at their concentrations in normal rat plasma. Glutamate formed from leucine remains mainly in the tissue, whereas that from glutamine enters the medium. The pancreatic Leu?Glu pathway uses the leucine carbons for net glutamate formation; the ?-amino group is not used; the stoichiometry is as follows: 1 mol of leucine yields 2 mol of glutamate (2 leucine carbons per glutamate) plus 2 mol of CO2. Comparison of the Leu?Glu pathway in preparations of whole pancreatic segments, isolated acini, and islets of Langerhans localizes it in the acini; relatively high activity is found in cultures of the AR42J cell line and very little in the INS-1 832/13 cell line. Pancreatic tissue glutamate concentration is homeostatically regulated in the range of ?1-3 ?mol/g wet wt. l-Valine and leucine ethyl, benzyl, and tert-butyl esters inhibit the Leu?Glu pathway without decreasing tissue total glutamate. PMID:24699330

Schachter, David; Buteau, Jean

2014-06-01

77

A Hydrolase from Lactobacillus sakei Moonlights as a Transaminase  

PubMed Central

Enzymatic transamination of amino acids yields ?-keto acids and is the initial step for the production of volatile compounds that contribute to the sensory perception of fermented foods such as salami. Lactobacillus sakei is one of the lactic acid bacterial strains commonly used in starter cultures. Although the genome sequence of L. sakei 23K lacks genes encoding typical branched-chain amino acid transaminases, transamination activity and the formation of amino acid-derived volatile metabolites could be demonstrated. A protein purified from L. sakei is held responsible for the transamination activity. By heterologous expression of the corresponding gene in Escherichia coli, we were able to characterize the transamination side activity of an enzyme annotated as a putative acylphosphatase (AcP). A transamination side activity of hen egg white lysozyme (HEWL) was also discovered. Both enzymes showed substrate specificity toward branched-chain and aromatic amino acids. AcP also accepted l-methionine. Activity was optimal at neutral pH for both enzymes, whereas AcP showed a significantly higher temperature optimum (55°C) than that of HEWL (37°C). Kinetic parameters revealed high affinity toward l-leucine for AcP (Km = 1.85 mM) and toward l-isoleucine for HEWL (Km = 3.79 mM). AcP seems to play a major role in the metabolism of amino acids in L. sakei. PMID:23354716

Sinz, Quirin; Freiding, Simone; Vogel, Rudi F.

2013-01-01

78

A Molecular Dynamics Simulation Study of Two Dipeptide Based Molecular Micelles: Effect of Amino Acid Order.  

PubMed

Molecular dynamics (MD) simulations were used to compare the structures of the chiral molecular micelles (MM) poly-(sodium undecyl-(L,L)-leucine-valine) (poly(SULV)) and poly-(sodium undecyl-(L,L)-valine-leucine) (poly (SUVL)). Both MM contained polymerized surfactant monomers tenninated by chiral dipeptide headgroups. The study was undertaken to investigate why poly(SULV) is generally a better chiral selector compared to poly(SUVL) in electrokinetic chromatography separations. When comparing poly(SULV) to poly(SUVL), poly(SULV) had the more conformational flexible dipeptide headgroup and hydrogen bond analyses revealed that the poly(SULV) headgroup conformation allowed a larger number of intramolecular hydrogen bonds to form between monomer chains. In addition, a larger number of water molecules surrounded the chiral centers of the poly(SULV) molecular micelle. Poly(SULV) was also found to have a larger solvent accessible surface area (SASA) than poly(SUVL) and fluctuations in the poly(SULV) SASA during the MD simulation allowed dynamic monomer chain motions expected to be important in chiral recognition to be identified. Finally, approximately 50% of the Na(+) counterions were found in the first three solvation shells surrounding both MM, with the remainder located in the bulk. Overall the MD simulations point to both greater headgroup flexibility and solvent and analyte access to the chiral centers of the dipeptide headgroup as factors contributing to the enhanced chiral selectivity observed with poly(SULV). PMID:23951550

Morris, Kevin F; Billiot, Eugene J; Billiot, Fereshteh H; Lipkowitz, Kenny B; Southerland, William M; Fang, Yayin

2013-02-01

79

Preferential Treatment: Interaction Between Amino Acids and Minerals  

NASA Astrophysics Data System (ADS)

Amino acids are the building blocks of proteins and are important for some models of the origin of life. Polymerization of amino acids from dilute solution is unlikely without a scaffold or catalyst. The surfaces of early Earth minerals are the most likely candidates for this role. The surface adsorption behavior of 12 amino acids (L-alanine, L-serine, L-aspartic acid, L-proline, L- phenylalanine, L-valine, L-arginine, d-amino valeric acid, glycine, L-lysine, L-isoleucine, and B-alanine) on 21 minerals (quartz, calcite, enstatite, illite, olivine, pyrrhotite, pyrite, alkali basalt, albite, analcime, chlorite, barite, hydroxyl apatite, hematite, magnetite, aluminum hydroxide, kaolin, silica gel, corundum, rutile, and montmorillonite) was determined via batch adsorption experiments. Absorption was determined for concentrations between 10-4M and 10-6M in the presence of 0.1M NaCl, and between pH values of 3 and 9 at 25 degrees C. The equilibrated solutions were centrifuged, filtered, derivatized using a fluorescent amino group tag (dansyl-chloride) and analyzed by HPLC. Adsorption was standardized using BET surface area measurements for each mineral to give the number of mols of each amino acid adsorbed per square meter for each mineral. The results indicate an enormous difference in the adsorption of amino acids between minerals, along with major differences in the adsorption of individual amino acids on the same mineral surface. There is also a change in the absorbance of amino acids as the pH changes. Many previous studies of amino acid concentration and catalysis by minerals have used clay minerals because of their high surface areas, however, this data suggests that the surfaces of minerals such as calcite, quartz and pyrite have even higher affinities for amino acids. The results suggest mineral surfaces that could be optimal locations for the polymerization of molecules linked to the origin of life.

Crapster-Pregont, E. J.; Cleaves, H. J.; Hazen, R. M.

2008-12-01

80

Diversity of L-leucine catabolism in various microorganisms involved in dairy fermentations, and identification of the rate-controlling step in the formation of the potent flavour component 3-methylbutanal.  

PubMed

Various microorganisms, belonging to the genera Lactococcus, Lactobacillus, Streptococcus, Leuconostoc, Bifidobacterium, Propionibacterium, Brevibacterium, Corynebacterium and Arthrobacter, used in dairy fermentations such as cheese making, were analysed for their potential to convert leucine into flavour components, most notably 3-methylbutanal. A large variation between and within species was observed for various enzyme activities involved in the conversion pathway, e.g. transaminases, alpha-hydroxy acid dehydrogenase and alpha-keto acid decarboxylase. In particular, alpha-keto acid decarboxylase activity-leading to 3-methylbutanal-was found to be present in only two of the strains tested. It is proposed that this activity is rate-controlling in the conversion pathway leading to the flavour compound 3-methylbutanal. PMID:14624315

Smit, B A; Engels, W J M; Wouters, J T M; Smit, G

2004-04-01

81

Self-assembly thermodynamics of pH-responsive amino-acid-based polymers with a nonionic surfactant.  

PubMed

The behavior of pH-responsive polymers poly(N-methacryloyl-l-valine) (P1), poly(N-methacryloyl-l-phenylalanine) (P2), and poly(N-methacryloylglycyne-l-leucine) (P3) has been studied in the presence of the nonionic surfactant Brij98. The pure polymers phase-separate in an acidic medium with critical pHtr values of 3.7, 5.5, and 3.4, respectively. The addition of the surfactant prevents phase separation and promotes reorganization of polymer molecules. The nature of the interaction between polymer and surfactant depends on the amino acid structure in the side chain of the polymer. This effect was investigated by dynamic light scattering, isothermal titration calorimetry, electrophoretic measurements, small-angle neutron scattering, and infrared spectroscopy. Thermodynamic analysis revealed an endothermic association reaction in P1/Brij98 mixture, whereas a strong exothermic effect was observed for P2/Brij98 and P3/Brij98. Application of regular solution theory for the analysis of experimental enthalpograms indicated dominant hydrophobic interactions between P1 and Brij98 and specific interactions for the P2/Brij98 system. Electrophoretic and dynamic light scattering measurements support the applicability of the theory to these cases. The specific interactions can be ascribed to hydrogen bonds formed between the carboxylic groups of the polymer and the oligo(ethylene oxide) head groups of the surfactant. Thus, differences in polymer-surfactant interactions between P1 and P2 polymers result in different structures of polymer-surfactant complexes. Specifically, small-angle neutron scattering revealed pearl-necklace complexes and "core-shell" structures for P1/Brij98 and P2/Brij98 systems, respectively. These results may help in the design of new pH-responsive site-specific micellar drug delivery systems or pH-responsive membrane-disrupting agents. PMID:25192406

Bogomolova, Anna; Keller, Sandro; Klingler, Johannes; Sedlak, Marian; Rak, Dmytro; Sturcova, Adriana; Hruby, Martin; Stepanek, Petr; Filippov, Sergey K

2014-09-30

82

Crystallization of Amino Acids on a 21-well Circular PMMA Platform using Metal-Assisted and Microwave-Accelerated Evaporative Crystallization.  

PubMed

We describe the design and the use of a circular poly(methyl methacrylate) (PMMA) crystallization platform capable of processing 21 samples in Metal-Assisted and Microwave-Accelerated Evaporative Crystallization (MA-MAEC). The PMMA platforms were modified with silver nanoparticle films (SNFs) to generate a microwave-induced temperature gradient between the solvent and the SNFs due to the marked differences in their physical properties. Since amino acids only chemisorb on to silver on the PMMA platform, SNFs served as selective and heterogeneous nucleation sites for amino acids. Theoretical simulations for electric field and temperature distributions inside a microwave cavity equipped with a PMMA platform were carried out to determine the optimum experimental conditions, i.e., temperature variations and placement of the PMMA platform inside a microwave cavity. In addition, the actual temperature profiles of the amino acid solutions were monitored for the duration of the crystallization experiments carried out at room temperature and during microwave heating. The crystallization of five amino acids (L-threonine, L-histidine, L-leucine, L-serine and L-valine HCl) at room temperature (control experiment) and using MA-MAEC were followed by optical microscopy. The induction time and crystal growth rates for all amino acids were determined. Using MA-MAEC, for all amino acids the induction times were significantly reduced (up to ~8-fold) and the crystal growth rates were increased (up to ~50-fold) as compared to room temperature crystallization, respectively. All crystals were characterized by Raman spectroscopy and powder x-ray diffraction, which demonstrated that the crystal structures of all amino acids grown at room temperature and using MA-MAEC were similar. PMID:24855565

Alabanza, Anginelle M; Mohammed, Muzaffer; Aslan, Kadir

2013-01-01

83

Polymers from amino acids: development of dual ester-urethane melt condensation approach and mechanistic aspects.  

PubMed

A new dual ester-urethane melt condensation methodology for biological monomers-amino acids was developed to synthesize new classes of thermoplastic polymers under eco-friendly and solvent-free polymerization approach. Naturally abundant L-amino acids were converted into dual functional ester-urethane monomers by tailor-made synthetic approach. Direct polycondensation of these amino acid monomers with commercial diols under melt condition produced high molecular weight poly(ester-urethane)s. The occurrence of the dual ester-urethane process and the structure of the new poly(ester-urethane)s were confirmed by (1)H and (13)C NMR. The new dual ester-urethane condensation approach was demonstrated for variety of amino acids: glycine, ?-alanine, L-alanine, L-leucine, L-valine, and L-phenylalanine. MALDI-TOF-MS end group analysis confirmed that the amino acid monomers were thermally stable under the melt polymerization condition. The mechanism of melt process and the kinetics of the polycondensation were studied by model reactions and it was found that the amino acid monomer was very special in the sense that their ester and urethane functionality could be selectively reacted by polymerization temperature or catalyst. The new polymers were self-organized as ?-sheet in aqueous or organic solvents and their thermal properties such as glass transition temperature and crystallinity could be readily varied using different l-amino acid monomers or diols in the feed. Thus, the current investigation opens up new platform of research activates for making thermally stable and renewable engineering thermoplastics from natural resource amino acids. PMID:22713137

Anantharaj, S; Jayakannan, M

2012-08-13

84

Dried Bonito Dashi: Taste Qualities Evaluated Using Conditioned Taste Aversion Methods in Wild-Type and T1R1 Knockout Mice.  

PubMed

The primary taste of dried bonito dashi is thought to be umami, elicited by inosine 5'-monphosphate (IMP) and l-amino acids. The present study compared the taste qualities of 25% dashi with 5 basic tastes and amino acids using conditioned taste aversion methods. Although wild-type C57BL/6J mice with compromised olfactory systems generalized an aversion of dashi to all 5 basic tastes, generalization was greater to sucrose (sweet), citric acid (sour), and quinine (bitter) than to NaCl (salty) or monosodium l-glutamate (umami) with amiloride. At neutral pH (6.5-6.9), the aversion generalized to l-histidine, l-alanine, l-proline, glycine, l-aspartic acid, l-serine, and monosodium l-glutamate, all mixed with IMP. Lowering pH of the test solutions to 5.7-5.8 (matching dashi) with HCl decreased generalization to some amino acids. However, adding lactic acid to test solutions with the same pH increased generalization to 5'-inosine monophosphate, l-leucine, l-phenylalanine, l-valine, l-arginine, and taurine but eliminated generalization to l-histidine. T1R1 knockout mice readily learned the aversion to dashi and generalized the aversion to sucrose, citric acid, and quinine but not to NaCl, glutamate, or any amino acid. These results suggest that dashi elicits a complex taste in mice that is more than umami, and deleting T1R1 receptor altered but did not eliminate their ability to taste dashi. In addition, lactic acid may alter or modulate taste transduction or cell-to-cell signaling. PMID:25604941

Delay, Eugene R; Kondoh, Takashi

2015-02-01

85

Optimum conditions for prebiotic evolution in extraterrestrial environments  

NASA Astrophysics Data System (ADS)

The overall goal of the dissertation was to devise synthetic pathways leading to the production of peptides and amino acids from smaller organic precursors. To this end, eight different zeolites were tested in order to determine their catalytic potential in the conversion of amino acids to peptides. The zeolites tested were either synthetic or naturally occurring. Acidic solutions of amino acids were prepared with or without zeolites and their reactivity was monitored over a four-week time interval. The kinetics and feasibility of peptide synthesis from selected amino acid combinations was investigated via the paper chromatography technique. Nine different amino acids were tested. The nature and extent of product were measured at constant time intervals. It was found that two ZSM-5 synthetic zeolites as well as the Fisher Scientific zeolite mix without alumina salts may have a catalytic potential in the conversion of amino acids to peptides. The conversion was verified by matching the paper chromatogram of the experimental product with that of a known peptide. The experimental results demonstrate that the optimum solvent system for paper chromatographic analysis of the zeolite-catalyzed self-assembly of the amino acids L-aspartic acid, L- asparagine, L-histidine, and L-serine is a 50:50 mixture of 1-butanol and acetone by volume. For the amino acids L-alanine, L-glycine, and L-valine, the optimum solvent was found to be a 30:70 mixture of ammonia and propanol by volume. A mathematical model describing the distance traveled (spot position) versus reaction time was constructed for the zeolite-catalyzed conversion of L- leucine and L-tyrosine and was found to approximately follow the function f(t) = 25 ln t. Two case studies for prebiotic synthesis leading to the production of amino acids or peptides in extraterrestrial environments were discussed: one involving Saturn's moon Titan, and the other involving Jupiter's moon Europa. In the Titan study, it was determined that organic synthesis, based on simple precursors, may lead in the Titan environment to the production of biologically important molecules such as amino acids. In the Europa study, three synthetic schemes using hydrogen peroxide, sulfuric acid, and hydrocyanic acid, and leading to the production of larger biologically important molecules such as amino acids were presented. (Abstract shortened by UMI.)

Abbas, Ousama H.

86

Efficacy of a spray compound containing a pool of collagen precursor synthetic aminoacids (l-proline, l-leucine, l-lysine and glycine) combined with sodium hyaluronate to manage chemo/radiotherapy-induced oral mucositis: preliminary data of an open trial.  

PubMed

Oral mucositis (OM) is a very frequent and potentially severe complication experienced by patients receiving chemotherapy and/or radiotherapy, which often leads to significant morbidity and mortality, and decreased quality of life, and is very costly. Despite its severity and prevalence, there is no standard recognised management today. The aim of this open clinical trial is to evaluate the efficacy and compliance of a new spray compound containing sodium hyaluronate (SH) and a pool of collagen precursor amino acids (AAs) combined with sodium hyaluronate (SH) to manage radio/chemotherapy-induced OM. Twenty-seven consecutive patients with OM were treated according to the manufacturers instructions. At time T0 (baseline before intervention), we evaluated the following parameters: (i) pain score (by linear visual analogue scale; 0100) and (ii) severity of OM scored according to WHO Mucositis scale. The treatment efficacy was evaluated on i) pain score, ii) clinical resolution index (CRI) and iii) patient compliance at times T01 (after 2 hours), T1 (after 24 hours), T2 (after 72 hours), T3 (after 7 days) and T4 (after 14 days). Results showed that painful symptoms were significantly reduced after only 2 hours of spray administration compared with baseline measurements (p less than 0.0001; z=-4.541). A progressive reduction of pain through the 2 weeks was also noted (p less than 0.0001). Patient lesions treated with SH-Asbased spray also significantly improved after 72 hours of treatment (p=0.0051; z=-2.803). During the two-week observation, all patients significantly improved from the baseline (p less than 0.0001) and progressively ameliorated their ability to swallow foods and liquids. The compliance of all patients to the product was very good, and at the end of the study there were no adverse effects. The results suggest that the SHAAs-based spray accelerates lesion healing and above all helps to manage mucositis pain, especially in terms of immediate pain relief (after 2 hours from application). Although further randomized controlled studies are recommended, our findings suggest that frequent applications of this spray may offer rapid and effective pain management, aiding faster mucosal wound healing. PMID:20378002

Colella, G; Cannavale, R; Vicidomini, A; Rinaldi, G; Compilato, D; Campisi, G

2010-01-01

87

Synthesis of N-carbobenzoxy-L-valyl-L-valyl-4-amino-3-hydroxy-5-methylhexanoic acid  

E-print Network

is extended to my wife, Corlis, for typing this thesis and her continued support during my graduate work. TABLE OF CONTENTS INTRODUCT1ON RESULTS AND DISCUSSION Synthesis of Ethyl 4-Amino-3-hydroxy-5- methylhexanoate Hydrochloride, Coupling Procedures...)-N-t-Butyloxycarbonyl-4-amino- 3-hydroxy-5-methylhexanoate (17a, 17b) Ethyl (38, 4S)-4-Amino-3-hydroxy-5-methylhexanoate Hydrochloride (18a). N-Carbobenzoxy-L-valine (19) Ethyl L-Valinate Hydrochloride (20). Ethyl N-Carbobenzoxy-L-valyl-L-valinate (21) N...

Hicks, Gary Dean

1980-01-01

88

Methyl 2-(methylthio)benzoate: A sex attractant for the June beetles, Phyllophaga tristis and P. apicata  

Technology Transfer Automated Retrieval System (TEKTRAN)

Male antennae of Phyllophaga tristis (Fabricius) (Coleoptera: Scarabaeidae: Melolonthinae) were tested using a coupled gas chromatograph-electroantennogram detector (GC-EAD) system for electrophysiological responses to five sex pheromones identified from other Phyllophaga species including L-valine ...

89

The Relationship between Dipeptidase Activity Variation and Larval Viability in Drosophila melanogaster  

PubMed Central

The enzyme dipeptidase-A (DIP-A) in Drosophila melanogaster is coded by a second chromosome locus that is polymorphic for three allozymes in natural populations. DIP-A appears to be the only enzyme in D. melanogaster capable of hydrolyzing the dipeptide glycyl-l-isoleucine, since flies homozygous for null alleles at this locus have no detectable glycyl- l-isoleucine-ase activity. DIP-A activity occurs in many tissues and throughout development, but is particularly high in the larval midgut, suggesting an important role in protein digestion. These observations suggested an experimental design for investigating the adaptive significance of genetic variation in DIP-A activity. Fitness components of DIP-A variants could be estimated and compared under two environmental conditions (defined diets under axenic conditions). In the restrictive environment, the essential amino acid l-isoleucine is provided only in the form of glycyl-l-isoleucine, whereas in the permissive environment, l-isoleucine is provided in free form. We predicted that DIP-A activity would be essential in the restrictive, but not in the permissive environment. The results reported here clearly contradict this prediction. Two stocks homozygous for DIP-A null alleles from different geographic locations are each viable on the restrictive diet. Furthermore, relative viability experiments in which null allele larvae compete with larvae having DIP-A activity provide no evidence for even a partial reduction in egg to adult survival on the restrictive diet. Apparently, the null allele larvae have some alternative mechanism for obtaining l-isoleucine from the dipeptide, even though no glycyl-l-isoleucine-ase activity can be detected in vitro. These results, along with the viability of null alleles for many other enzymes, support the idea that eukaryotes have an intricate network of alternative biochemical pathways through which the same necessary function may be achieved. Such "buffering capacity" makes it very difficult to analyze the effects of enzyme variants on fitness components. PMID:3121435

Hiraizumi, Kazuo; Laurie, Cathy C.

1987-01-01

90

Stereoselective evasion of P-glycoprotein, cytochrome P450 3A, and hydrolases by peptide prodrug modification of saquinavir.  

PubMed

In an approach to overcome biological barriers mediated by P-glycoprotein (P-gp) and cytochrome P450 3A (CYP3A), a series of stereoisomeric valine-valine prodrugs of saquinavir (SQV) were synthesized and investigated with respect to affinity for efflux pump P-gp, and resistance to oxidative and hydrolytic enzymes. Cellular uptake and bidirectional transport in Caco-2 cells indicated that all peptide SQV conjugates can bypass P-gp-mediated efflux significantly, regardless of stereochemistry in promoieties. In comparison with D-configuration, L-configuration was favored for the interaction between prodrugs and rat hepatic CYP3A enzymes, and resulted in a relatively rapid clearance by CYP3A. Elimination half-life of SQV in rat liver microsomes was prolonged dramatically by sevenfold to 40-fold because of the prodrug modification with the rank order of D-valine-D-valine-SQV > D-valine-L-valine-SQV > L-valine-D-valine-SQV > L-valine-L-valine-SQV > D-valine-SQV > L-valine-SQV > SQV. Results of hydrolysis studies performed in rat intestinal homogenates and plasma indicated that prodrugs attached with D-valine exhibited significantly reduced biodegradation. In conclusion, the enhanced transepithelial accumulation and enzymatic stability observed by SQV peptide prodrug modification are found to be stereoselective. Specific stereoisomeric dipeptide prodrugs with optimized metabolic stability can be employed to improve oral bioavailability of SQV. PMID:22611042

Wang, Zhiying; Pal, Dhananjay; Mitra, Ashim K

2012-09-01

91

BACTERIOPLANKTON DYNAMICS IN A SUBTROPICAL ESTUARY: EVIDENCE FOR SUBSTRATE LIMITATION  

EPA Science Inventory

Bacterioplankton abundance and metabolic characteristics were measured along a transect in Pensacola Bay, Florida, USA, to examine the factors that control microbial water column processes in this subtropical estuary. The microbial measures included 3 H-L-leucine incorporation, e...

92

Polypeptide grafted hyaluronan: A self-assembling comb-branched polymer constructed from biological components  

PubMed Central

Rheological evidence is provided demonstrating that covalent grafting of monodisperse isotactic poly(L-leucine) branches onto linear hyaluronan (HA) polysaccharide chains yields comb-branched HA chains that self-assemble into long-lived physical networks in aqueous solutions driven by hydrophobic interactions between poly(L-leucine) chains. This is in stark contrast to native (unmodified) HA solutions which exhibit no tendency to form long-lived physical networks. PMID:22021933

Kandadai, Madhuvanthi A.; Anumolu, Rajasekhar; Wang, Xiaojun; Baskaran, Durairaj; Pease, Leonard F.; Bedrov, Dmitry; Smith, Grant D.; Mays, Jimmy W.; Magda, Jules J.

2011-01-01

93

Expression and functional characterization of the system l amino acid transporter in KB human oral epidermoid carcinoma cells  

Microsoft Academic Search

We have examined the expression and function of system l amino acid transporter in KB human oral epidermoid carcinoma cells. The KB cells express l-type amino acid transporter 1 (LAT1) in plasma membrane, but not l-type amino acid transporter 2 (LAT2). The [14C]l-leucine uptake by KB cells is inhibited by system l selective inhibitor BCH. The majority of [14C]l-leucine uptake

Jung Hoon Yoon; Youn Bae Kim; Myong Soo Kim; Joo Cheol Park; Joong Ki Kook; Hae Man Jung; Saeng Gon Kim; Hoon Yoo; Yeong Mu Ko; Sang Ho Lee; Bong Young Kim; Hong Sung Chun; Yoshikatsu Kanai; Hitoshi Endou; Do Kyung Kim

2004-01-01

94

Regulation of transmural transport of amino acid/metal conjugates by dietary calcium in crustacean digestive tract.  

PubMed

Effects of luminal Ca(2+) and Mn(2+) on transmural mucosal to serosal (MS) transport of (3) H-L-leucine were characterized in the isolated and perfused intestine of the American lobster, Homarus americanus. (3) H-L-leucine MS transport in the presence of 20 µM Mn(2+) was a sigmoidal function of luminal amino acid concentration, following the Hill equation for multisite cooperative, carrier-mediated, transport. Luminal Ca(2+) was a non-competitive inhibitor of Mn(2+) -stimulated (3) H-L-leucine MS flux. Amino acid transport was hyperbolically stimulated by luminal Ca(2+) or Mn(2+). During 20 µM Mn(2+) -stimulation of (3) H-L-leucine MS flux, addition of 25 mM Ca(2+) strongly reduced amino acid transport Jmax , without affecting amino acid binding properties. Hyperbolic luminal Mn(2+) stimulation of 20 µM (3) H-L-leucine MS flux was also strongly inhibited by 25 mM luminal Ca(2+) , significantly reducing 20 µM (3) H-L-leucine Jmax . Increasing the luminal concentration of verapamil, a calcium channel blocker, significantly increased MS transport of 20 µM (3) H-L-leucine in the presence of 100 nM Mn(2+) by reducing diffusional Ca(2+) uptake into intestinal epithelial cells through verapamil-sensitive channels. A model is proposed supporting the concept of molecular mimicry, whereby (3) H-L-leucine enters lobster intestinal epithelial cells by one or more amino acid-specific transporters and by a dipeptide-like transporter that is capable of binding and transporting peptide molecular mimics (bis-complexes) between Ca(2+) or Mn(2+) and (3) H-L-leucine using the membrane potential as a major driving force for the transport event. According to the model, Ca(2+) entry through apical Ca(2+) channels regulates the magnitude of the membrane potential and therefore the size of the driving force for bis-complex uptake. PMID:24254522

Abdel-Malak, Rania; Ahearn, Gregory A

2014-03-01

95

Evaluation of Surface Damage of Organic Films due to Irradiation with Energetic Ion Beams  

SciTech Connect

The surface of L-leucine films irradiated with an Ar{sub 5000} cluster ion beam (5 keV) was characterized by using the X-ray reflective (XRR) measurement method, atomic force microscopy (AFM) and ellipsometry. No significant damage was detected on the surface of the L-leucine films irradiated with the Ar cluster ion beam. Therefore, the large cluster-low-energy (about 1 eV/atom) beam would be suitable for low-damage etching of organic materials.

Hada, Masaki; Hontani, Yusaku; Ichiki, Kazuya; Seki, Toshio [Department of Nuclear Engineering, Kyoto University, Sakyo, Kyoto, 606-8501 (Japan); Ibuki, Sachi; Ninomiya, Satoshi; Matsuo, Jiro [Quantum Science and Engineering Center, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Aoki, Takaaki [Department of Electronic Science and Engineering, Kyoto University, Nishigyo, Kyoto, 615-8530 (Japan)

2011-01-07

96

Amino acid derivatives of 5ASA as novel prodrugs for intestinal drug delivery  

Microsoft Academic Search

In an attempt to obtain site-specific delivery of 5-ASA in the intestinal tract, we have determined the extent of absorption and metabolism of a number of novel 5-ASA derivatives, namely, (N-l-glutamyl)-amino-2-salicylic acid (1), (N-l-aspartyl)-amino-2-salicylic-acid (2), 5-aminosalicyl-l-proline-l-leucine (3), and 5-(N-l-glutamyl)-aminosalicyl-l-proline-l-leucine (4), which are selectively cleaved by intestinal brush border aminopeptidase A and carboxypeptidases. These novel prodrugs, 5-ASA, and sulfasalazine were administered

Carlo Clerici; Giorgio Gentili; Enrico Boschetti; Carla Santucci; Aaron Garzon Aburbeh; Benedetto Natalini; Roberto Pellicciari; Antonio Morelli

1994-01-01

97

[Biosynthesis of enniatin by washed cells of Fusarium sambucinum].  

PubMed

Biosynthesis of the depsipeptide membrane ionophore--enniatin B by the washed mycelium Fusarium sambucinum Fuck 52 377 was studied. Metabolic precursors of enniatin B, alpha-ketovaleric acid, 14C-L-valine, and 14CH3-methionine, were added to the system after starvation. The amino acid content in the metabolic pool increased 1.5 times after addition of alpha-ketovaleric acid, 2.2 times after that of valine, and 2.5 times after addition of methionine. 14C-L-valine and 14CH3-methionine were incorporated into the molecule of enniatin B. Valine methylation in the molecule occurred at the level of synthesized depsipeptide. Amino acids of the metabolic pool performed the regulatory function in the synthesis. PMID:583180

Minasian, A E; Chermensk?, D N; Bezborodov, A M

1979-01-01

98

AUTORADIOGRAPHIC STUDY OF SUGAR AND AMINO ACID ABSORPTION BY EVERTED SACS OF HAMSTER INTESTINE  

Microsoft Academic Search

Autoradiographs were prepared from frozen sections of evcrted sacs of hamster jejunum which had been incubated in vitro with C 14- or H~-labcled sugars and amino acids. When such tissue was incubated in 1 mM solutions of L-valine or L-methionine, columnar absorp- tivc cells at tips of villi accumulated these amino acids to conccntrations ranging from 5 to 50 millimoles

WILLIAM B. KINTER; T. HASTINGS WILSON

1965-01-01

99

Quantitative HPLC Determination of Ciphelin  

Microsoft Academic Search

N-[N-Acetyl-p-di(2-chloroethyl)amino-D,L-phenylalanine]-D,L-valine ethyl ester (ciphelin) is an original domestic antitumor preparation possessing alkylating activity, which was synthesized and characterized at the Blokhin Oncological Research Center (Moscow) [1 – 3]. With respect to the antitumor activity spectrum, ciphelin is fully analogous to sarcolysin and cyclophosphane. A distinguishing feature of these drugs is that, while producing the same action upon tumor, ciphelin exhibits

A. P. Arzamastsev; N. V. Valova; N. A. Oborotova

2001-01-01

100

Ferroelectric studies on amino acids mixed TGSP single crystals  

Microsoft Academic Search

Amino acids mixed TGS crystals are of interest due to their high pyroelectric coefficient and low dielectric constant. Partial substitution of phosphate has resulted in triglycine sulpho-phosphate (TGSP), a mixed crystal with improved pyroelectric figure of merit. In order to study the effect of amino acids on the ferroelectric properties of TGSP, we have substituted l-alanine (ATGSP), l-valine (VTGSP), l-asparagine

G. Arunmozhi; R. Jayavel; C. Subramanian

1998-01-01

101

Growth of Various Amino-Acid-Doped Triglycine Sulfate Crystals and Their Ferroelectric Properties  

Microsoft Academic Search

Single crystals of triglycine sulfate (TGS) were grown from solutions containing 10 mol% of L-alpha-alanine, DL-alpha-alanine, sarcosine, L-serine or L-valine. The crystal form, domain structure and internal bias field Eb of these crystals were investigated. The crystal form and macroscopic distribution of Eb in crystals doped with L-alpha-alanine and L-serine show polar symmetry 2, and those in crystals with DL-alpha-alanine

Noriyuki Nakatani

1993-01-01

102

The effect of puromycin on protein metabolism and cell division in fertilized sea urchin eggs  

Microsoft Academic Search

Résumé La puromycine inhibe fortement l'incorporation de la14C-L-valine dans les protéines, aussi bien dans les œufs fécondés d'oursins intacts que dans les préparations subcellulaires faites à partir de ceux-ci. Cependant ces préparations se sont montrées nettement plus sensibles à l'action de la puromycine que les œufs entiers. Parallèlement le blocage des divisions cellulaires a été proportionnel à cette action inhibitrice

T. Hultin

1961-01-01

103

Effects of ¹?C-labelled precursor feeding on production of beauvericin, enniatins H, I, and MK1688 by Fusarium oxysporum KFCC11363P.  

PubMed

The effects of ¹?C-labelled precursor feeding on the production of cyclic hexadepsipeptides were investigated by the mycelium of F. oxysporum KFCC11363P producing beauvericin along with enniatins H, I, and MK1688. Most ¹?C-phenylalanine and ¹?C-valine were incorporated easily into the biosynthetic pathway of ¹?C-labelled beauvericin in vivo by the mycelium. However, only a small amount of ¹?C-labelled enniatins could be detected by feeding of ¹?C-valine. When L-valine was fed as a precursor to the mycelium at large scale, the level of beauvericin increased to maximum followed by enniatins H and I. Feeding of L-valine did not affect the production of enniatin MK1688. These results suggest that L-valine feeding led to the production of D-hydroxyisovaleic acid in the mycelium and specifically enhanced the production of cyclic hexadepsipeptides containing D-hydroxyisovaleic acid, such as beauvericin and enniatins H and I. PMID:22019403

Lee, Hee-Seok; Kim, Kyung-Ai; Seo, Dong-Geun; Lee, Chan

2012-01-01

104

Effect of amino acid doping on the growth and ferroelectric properties of triglycine sulphate single crystals  

Microsoft Academic Search

Effect of amino acids (l-leucine and isoleucine) doping on the growth aspects and ferroelectric properties of triglycine sulphate crystals has been studied. Pure and doped crystals were grown from aqueous solution by low temperature solution growth technique. The cell parameter values were found to significantly vary for doped crystals. Fourier transform infrared analysis confirmed the presence of functional groups in

C. M. Raghavan; R. Sankar; R. Mohan Kumar; R. Jayavel

2008-01-01

105

Reconstitution studies of amino acid transport system L in rat erythrocytes.  

PubMed Central

In many cell types, including human erythrocytes, membrane transport of hydrophobic amino acids such as leucine and phenylalanine is mediated primarily by Na(+)-independent system L. In this paper we demonstrate that erythrocytes from the rat have a 400-fold higher system L transport capacity than human erythrocytes. We have exploited this high transport activity to achieve the first successful reconstitution of an erythrocyte amino acid transporter into phospholipid vesicles. Rat erythrocyte membranes were depleted of extrinsic membrane proteins, solubilized in 50 mM n-octyl glucoside and reconstituted into egg-yolk phospholipid vesicles by a gel filtration freeze-thaw protocol. Optimal reconstitution of transport activity occurred at lipid/protein ratios of 25-35:1. At a lipid/protein ratio of 25:1, one-half of the total uptake of L-[14C]leucine (0.2 mM, 25 degrees C) was inhibited by 2 mM phloretin and thus judged to be carrier-mediated. This component of L-leucine uptake was inhibited by non-radioactive L-phenylalanine and L-leucine, and only to a very much weaker extent by glycine and L-alanine. Two other inhibitors of system L in intact cells, MK196 and PCMBS (p-chloromercuriphenylsulphonate), were also effective inhibitors of phloretin-sensitive L-leucine transport in reconstituted proteoliposomes. Phloretin-insensitive uptake of L-leucine in proteoliposomes occurred by simple diffusion across the lipid bilayer. PMID:8317996

Yao, S Y; George, R; Young, J D

1993-01-01

106

Evolutionarily distinct versions of the multidomain enzyme ?-isopropylmalate synthase share discrete mechanisms of V-type allosteric regulation.  

PubMed

Understanding the evolution of allostery in multidomain enzymes remains an important step in improving our ability to identify and exploit structure-function relationships in allosteric mechanisms. A recent protein similarity network for the DRE-TIM metallolyase superfamily indicated there are two evolutionarily distinct forms of the enzyme ?-isopropylmalate synthase (IPMS) sharing approximately 20% sequence identity. IPMS from Mycobacterium tuberculosis has been extensively characterized with respect to catalysis and the mechanism of feedback regulation by l-leucine. Here, IPMS from Methanococcus jannaschii (MjIPMS) is used as a representative of the second form of the enzyme, and its catalytic and regulatory mechanism is compared with that of MtIPMS to identify any functional differences between the two forms. MjIPMS exhibits kinetic parameters similar to those of other reported IPMS enzymes and is partially inhibited by l-leucine in a V-type manner. Identical values of (D2O)kcat (3.1) were determined in the presence and absence of l-leucine, indicating the hydrolytic step is rate-determining in the absence of l-leucine and remains so in the inhibited form of the enzyme. This mechanism is identical to the mechanism identified for MtIPMS ((D2O)kcat = 3.3 ± 0.3 in the presence of l-leucine) despite product release being rate-determining in the uninhibited MtIPMS enzyme. The identification of identical regulatory mechanisms in enzymes with low sequence identity raises important evolutionary questions concerning the acquisition and divergence of multidomain allosteric enzymes and highlights the need for caution when comparing regulatory mechanisms for homologous enzymes. PMID:24991690

Kumar, Garima; Frantom, Patrick A

2014-07-29

107

Identification, Purification, and Characterization of a Novel Amino Acid Racemase, Isoleucine 2-Epimerase, from Lactobacillus Species  

PubMed Central

Accumulation of d-leucine, d-allo-isoleucine, and d-valine was observed in the growth medium of a lactic acid bacterium, Lactobacillus otakiensis JCM 15040, and the racemase responsible was purified from the cells and identified. The N-terminal amino acid sequence of the purified enzyme was GKLDKASKLI, which is consistent with that of a putative ?-aminobutyrate aminotransferase from Lactobacillus buchneri. The putative ?-aminobutyrate aminotransferase gene from L. buchneri JCM 1115 was expressed in recombinant Escherichia coli and then purified to homogeneity. The enzyme catalyzed the racemization of a broad spectrum of nonpolar amino acids. In particular, it catalyzed at high rates the epimerization of l-isoleucine to d-allo-isoleucine and d-allo-isoleucine to l-isoleucine. In contrast, the enzyme showed no ?-aminobutyrate aminotransferase activity. The relative molecular masses of the subunit and native enzyme were estimated to be about 49 kDa and 200 kDa, respectively, indicating that the enzyme was composed of four subunits of equal molecular masses. The Km and Vmax values of the enzyme for l-isoleucine were 5.00 mM and 153 ?mol·min?1·mg?1, respectively, and those for d-allo-isoleucine were 13.2 mM and 286 ?mol·min?1·mg?1, respectively. Hydroxylamine and other inhibitors of pyridoxal 5?-phosphate-dependent enzymes completely blocked the enzyme activity, indicating the enzyme requires pyridoxal 5?-phosphate as a coenzyme. This is the first evidence of an amino acid racemase that specifically catalyzes racemization of nonpolar amino acids at the C-2 position. PMID:24039265

Mutaguchi, Yuta; Ohmori, Taketo; Wakamatsu, Taisuke; Doi, Katsumi

2013-01-01

108

Isoleucine as a possible bridge between exogenous delivery and terrestrial enhancement of homochirality.  

PubMed

We report a highly enantioselective oligomerization of isoleucine stereomers in the salt-induced peptide formation reaction under plausibly prebiotic earth conditions. Up to 6.5-fold superiority in reactivity of L-isoleucine was observed, compared to its D-enantiomer, after 14 evaporation cycles in the presence of Cu(2+) and NaCl. Since isoleucine is among the proteinogenic amino acids that were found enantioenriched in meteorites, this present work may further correlate the extraterrestrial delivery and endogenous production of biological homochirality by virtue of a protein constituent rather than the rarely occurring ?-methylated amino acids. PMID:22968664

Li, Feng; Fitz, Daniel; Rode, Bernd M

2013-02-01

109

Sex pheromone of the scarab beetle Phyllophaga (Phytalus) georgiana (horn).  

PubMed

The sex pheromone of Phyllophaga (Phytalus) georgiana was characterized as valine methyl ester, tentatively the L-enantiomer. This is the first sex pheromone identified from the Phyllophaga subgenus Phytalus. The pheromone was extracted from female glands, the active component isolated by coupled gas chromatography-electroantennogram detection analysis, characterized by mass spectrometry, and shown to be active in field tests. The seasonal flight pattern was determined for P. georgiana as well as for three other species, P. anxia (both northern and southern genitalic forms), P. gracilis, and P. postrema. The latter three species were captured in traps baited with L-isoleucine methyl ester. PMID:19247715

Robbins, Paul S; Nojima, Satoshi; Polavarapu, Sridhar; Koppenhöfer, Albrecht M; Rodriguez-Saona, Cesar; Holdcraft, Robert J; Consolie, Nancy H; Peck, Daniel C; Roelofs, Wendell L

2009-03-01

110

Mutation of a single amino acid converts germ cell alkaline phosphatase to placental alkaline phosphatase.  

PubMed

Human placental and germ cell alkaline phosphatases (PLAP and GCAP, respectively), are characterized by their differential sensitivities to inhibition by L-leucine, EDTA, and heat. Yet, they differ by only 7 amino acids at positions 15, 67, 68, 84, 241, 254, and 429 within their respective 484 residues. To determine the structural basis and the amino acid(s) involved in these physicochemical differences, we constructed three GCAP mutants by site-directed mutagenesis and six GCAP/PLAP chimeras and then expressed these alkaline phosphatase mutants in COS-1 cells. We report that the differential reactivity of PLAP and GCAP depends critically on a single amino acid at position 429. GCAP with Gly-429 is strongly inhibited by L-leucine, EDTA, and heat, whereas PLAP with Glu-429 is resistant. By substituting Gly-429 of GCAP with a series of amino acids, we demonstrate that the relative sensitivities of these mutants to L-leucine, EDTA, and heat inhibition are, in general, parallel. Mutants in the order of resistance to these treatments are: Glu (most resistant), Asp/Ile/Leu, Gln/Val/Lys, Ser/His, and Arg/Thr/Met/Cys/Phe/Trp/Tyr/Pro/Asn/Ala/Gly (least resistant). However, the Ser-429 and His-429 mutants were more resistant to EDTA and heat inhibition than the wild-type GCAP, but were equally sensitive to L-leucine inhibition. Structural analysis of mammalian alkaline phosphatase modeled on the refined crystal structure of Escherichia coli alkaline phosphatase indicates that the negative charge of Glu-429 of PLAP, which simultaneously stabilizes the protein as a whole and the metal binding specifically, probably acts through interactions with the metal ligand His-320 (His-331 in E. coli alkaline phosphatase). Replacement of codon 429 with Gly in GCAP leads to destabilization and loosening of the metal binding. The data suggest that the natural binding site for L-leucine may be near position 429, with the amino and carboxyl groups of L-leucine interacting with bound phosphate and His-432 (His-412 in E. coli alkaline phosphatase), respectively. PMID:1939159

Watanabe, T; Wada, N; Kim, E E; Wyckoff, H W; Chou, J Y

1991-11-01

111

The vascular effects of different arginase inhibitors in rat isolated aorta and mesenteric arteries  

PubMed Central

Background and purpose Arginase and nitric oxide (NO) synthase share the common substrate L-arginine, and arginase inhibition is proposed to increase NO production by increasing intracellular levels of L-arginine. Many different inhibitors are used, and here we have examined the effects of these inhibitors on vascular tissue. Experimental approach Each arginase inhibitor was assessed by its effects on isolated rings of aorta and mesenteric arteries from rats by: (i) their ability to preserve the tolerance to repeated applications of the endothelium-dependent agonist acetylcholine (ACh); and (ii) their direct vasorelaxant effect. Key results In both vessel types, tolerance (defined as a reduced response upon second application) to ACh was reversed with addition of L-arginine, (S)-(2-boronethyl)-L-cysteine HCl (BEC) or NG-Hydroxy-L-arginine (L-NOHA). On the other hand, N?-hydroxy-nor-L-arginine (nor-NOHA) significantly augmented the response to ACh, an effect that was partially reversed with L-arginine. No effect on tolerance to ACh was observed with L-valine, nor-valine or D,L, ?-difluoromethylornithine (DFMO). BEC, L-NOHA and nor-NOHA elicited endothelium-independent vasorelaxation in both endothelium intact and denuded aorta while L-valine, DFMO and nor-valine did not. Conclusions and implications BEC and L-NOHA, but not nor-NOHA, L-valine, DFMO or nor-valine, significantly reversed tolerance to ACh possibly conserving L-arginine levels and therefore increasing NO bioavailability. However, both BEC and L-NOHA caused endothelium-independent vasorelaxation in rat aorta, suggesting that these inhibitors have a role beyond arginase inhibition alone. Our data thus questions the interpretation of many studies using these antagonists as specific arginase inhibitors in the vasculature, without verification with other methods. PMID:19133993

Huynh, NN; Harris, EE; Chin-Dusting, JFP; Andrews, KL

2009-01-01

112

A New Peptide Isolated from a Marine Derived Streptomyces bacillaris  

PubMed Central

A new peptide, l-O-Lac-l-Val-d-O-Hiv-d-Val (1), consisting of d-valine, l-valine, l-lactic acid, and 3-d-hydroxyisovaleric acid, was isolated from the culture of the marine sediment derived Streptomyces bacillaris. The planar structure of compound 1 was assigned by 1D, 2D NMR and mass spectroscopic analyses. Following acid and base hydrolysis, the absolute configuration of the valine residues in 1 were determined by application of the advanced Marfey’s method and the absolute configurations of hydroxy acids units were determined by a HPLC method based on Mosher’s reagents. PMID:22474960

Hu, Youcai

2014-01-01

113

Heterogeneous interaction between zwitterions of amino acids and glycerol in aqueous solutions at 298.15 K  

Microsoft Academic Search

The enthalpies of mixing of six kinds of amino acid (glycine, L-alanine, L-valine, L-serine, L-threonine, and L-proline) with\\u000a glycerol in aqueous solutions and the enthalpies of diluting of amino acid and glycerol aqueous solutions have been determined\\u000a by flow microcalorimetry at 298.15 K. Employing McMillan–Mayer theory, the enthalpies of mixing and diluting have been used\\u000a to calculate heterogeneous enthalpic pairwise interaction

Y. Li; Z. Yingyuan; L. Yonghui; J. Jing; W. Xiaoqing

2011-01-01

114

The pyruvate dehydrogenase complex of Corynebacterium glutamicum: an attractive target for metabolic engineering.  

PubMed

The pyruvate dehydrogenase complex (PDHC) catalyzes the oxidative thiamine pyrophosphate-dependent decarboxylation of pyruvate to acetyl-CoA and CO2. Since pyruvate is a key metabolite of the central metabolism and also the precursor for several relevant biotechnological products, metabolic engineering of this multienzyme complex is a promising strategy to improve microbial production processes. This review summarizes the current knowledge and achievements on metabolic engineering approaches to tailor the PDHC of Corynebacterium glutamicum for the bio-based production of l-valine, 2-ketosiovalerate, pyruvate, succinate and isobutanol and to improve l-lysine production. PMID:24486441

Eikmanns, Bernhard J; Blombach, Bastian

2014-12-20

115

Evaluation of a synthetic wound dressing capable of releasing silver sulfadiazine.  

PubMed

A silver sulfadiazine-impregnated poly-L-leucine wound dressing, AgSD-medicated wound dressing, was evaluated for antibacterial capacity against Pseudomonas aeruginosa and cytotoxicity to human fibroblasts and human epidermal keratinocytes. This wound dressing contained 0.4 mg AgSD/cm2. Antibacterial capacity was examined on experimentally infected wound surfaces (3.4 x 10(4) P. aeruginosa organisms/gm) on the dorsum of mice. The AgSD-medicated wound dressing showed effective bacterial control. Cytotoxicity was examined on a monolayer of cells formed in culture dishes. Cellular damage was reduced by the controlled release of AgSD from the hydrophobic poly-L-leucine sponge matrix of the AgSD-medicated wound dressing. Cytotoxicity of the AgSD-medicated wound dressing was much lower than that of 1% AgSD cream. PMID:1904876

Kuroyanagi, Y; Kim, E; Shioya, N

1991-01-01

116

Para-position derivatives of fungal anthelmintic cyclodepsipeptides engineered with Streptomyces venezuelae antibiotic biosynthetic genes  

Microsoft Academic Search

PF1022A, a cyclooctadepsipeptide possessing strong anthelmintic properties and produced by the filamentous fungus Rosellinia sp. PF1022, consists of four alternating residues of N-methyl-L-leucine and four residues of D-lactate or D-phenyllactate. PF1022A derivatives obtained through modification of their benzene ring at the para-position with nitro or amino groups act as valuable starting materials for the synthesis of compounds with improved anthelmintic

Naomi Sumida; Kaoru Okakura; Tatsuki Moriya; Manabu Watanabe; Takeshi Murakami; Koji Yanai

2004-01-01

117

Regulation of acetohydroxy acid synthase in Corynebacterium glutamicum during isoleucine formation from ?-hydroxybutyric acid  

Microsoft Academic Search

When Corynebacterium glutamicum ATCC 14310 (leu-) was cultured with 200 mg\\/l leucine and 150 mM a-hydroxybutyric acid the acetohydroxy acid synthase activity was increased to 0.17 U\\/mg as compared to 0.03 U\\/mg in the wildtype. This increase was a combined effect of the limiting amounts of leucine added, together with an apparent additional internal leucine\\/valine shortage resulting from accumulated a-ketobutyric

E. Scheer; C. Cordes; L. Eggeling; H. Sahm

1987-01-01

118

Metabolism as a function of water potential in air-dry seeds of charlock (Sinapis arvensis L. )  

Microsoft Academic Search

A new method is described for studying the metabolism of air-dry seeds. An initial pulse of ¹⁴COâ was supplied to seeds maintained in air at controlled low water potentials for 6 months. Seeds were also infiltrated with 2-¹⁴C-acetate and with ¹⁴C-L-leucine at 0°C, redried rapidly at 0°C, and maintained at controlled low water potentials for 4 to 6 weeks. The

M. Edwards

1976-01-01

119

Microbial uptake of dissolved organic matter in Mcmurdo Sound, Antarctica  

Microsoft Academic Search

The distribution and activity of bacterioplankton, and the turnover of dissolved organic matter (DOM) were examined in McMurdo Sound, Antarctica. On the eastern side of the Sound, bacteria averaged 6.5×108 l-1, and turnover rates of dissolved adenosine triphosphate, D-glucose and l-leucine averaged 16, 116 and 124 h, respecitvely. These molecules as well as thymidine were taken up maximally from 0°

R. E. Hodson; F. Azam; A. F. Carlucci; J. A. Fuhrman; D. M. Karl; O. Holm-Hansen

1981-01-01

120

Facilitated transport of amino acids across organic phases and the human erythrocyte membrane.  

PubMed Central

1. An artificial facilitated amino-acid-transfer process operating across a chloroform phase is reported. 2. This process utilizes a family of bis(salicylamidato)copper(II) complexes. 3. A mechanism is proposed for this process and for its sensitivity towards cyanide and bathophenanthroline sulphonate. 4. Facilitated transfer of L-leucine in human erythrocytes has been shown to be inhibited by bathophenanthroline sulphonate. PMID:7396879

Hider, R C; McCormack, W

1980-01-01

121

Direct spectrophotometric measurement of angiotensin I-converting enzyme inhibitory activity for screening bioactive peptides  

Microsoft Academic Search

A direct, extraction-free spectrophotometric assay was developed for determination of angiotensin I-converting enzyme activity (ACE) in the presence of ACE inhibitors using hippuryl-l-histidyl-l-leucine (HHL) as the ACE-specific substrate. This method relies on previously published spectrophotometric determination of hippuric acid (HA) content in the urine, the method of which was based on the specific colorimetric reaction of HA with benzene sulfonyl

Guan-Hong Li; Huan Liu; Yong-Hui Shi; Guo-Wei Le

2005-01-01

122

Zur Biogenese Flüchtiger Amine Beim Mutterkorn-Pilz Claviceps Purpurea  

Microsoft Academic Search

1.Washed mycelium of saprophytically grown Claviceps purpurea decarboxylates L-leucine, but not D-leucine, to iso-amylamine. The reaction was established in an experiment using 14C-labeled leucine. Mycelium incubated for 24 hours with leucine yielded 0.2–0.25 mg of iso-amylamine\\/g of dry weight of mycelium. These values corresponded to the optimal concentrations of iso-amylamine found in saprophytically grown cultures after 4–5 weeks of growth.2.Maximal

Thomas Hartmann

1965-01-01

123

The l-3,4-dihydroxyphenylalanine transporter in human and rat epithelial intestinal cells is a type 2 hetero amino acid exchanger  

Microsoft Academic Search

Information on the intestinal transport of l-3,4-dihydroxyphenylalanine (l-DOPA) is scarce. We present here the functional characteristics and regulation of the apical inward l-DOPA transport in two intestinal epithelial cell lines (human Caco-2 and rat IEC-6). The inward transfer of l-DOPA and l-leucine was promoted through an energy-driven system but with different sensitivity to extracellular Na+ concentration: a minor component of

Sónia Fraga; Maria Paula Serrão; Patr??cio Soares-da-Silva

2002-01-01

124

Substrate specificity of L-delta-(alpha-aminoadipoyl)-L-cysteinyl-D-valine synthetase from Cephalosporium acremonium: demonstration of the structure of several unnatural tripeptide products.  

PubMed Central

Potential substrates for L-delta-(alpha-aminoadipoyl)-L-(cysteinyl)-D-valine (ACV) synthetase were initially identified using both the amino-acid-dependent ATP<-->pyrophosphate exchange reaction catalysed by the enzyme and the incorporation of 14C-radiolabelled cysteine and valine into potential peptide products. S-Carboxymethylcysteine was an effective substitute for alpha-aminoadipate and both allylglycine and vinylglycine could substitute for cysteine, indicating that the thiol group of cysteine is not essential for peptide formation. L-allo-Isoleucine but not L-isoleucine substituted effectively for valine. The structures of the presumed peptide products derived from these amino acids were confirmed by combined use of electrospray-ionization m.s. (e.s.m.s.) and 1H n.m.r. These results clearly indicate that, in common with other peptide synthetases, but in contrast with ribosomal peptide synthesis, ACV synthetase has a relatively broad substrate specificity. PMID:8042979

Baldwin, J E; Shiau, C Y; Byford, M F; Schofield, C J

1994-01-01

125

Mixture of three amino acids as stabilizers replacing albumin in lyophilization of new third generation recombinant factor VIII GreenGene F.  

PubMed

A formulation with stabilizers replacing albumin was developed for lyophilization of recombinant factor VIII (FVIII), GreenGene F (WHO INN: beroctocog alfa), to achieve stability and eliminate safety issues of blood-derived albumin. L-Arginine (hydrophilic amino acid, positively charged side chain), L-glutamic acid (hydrophilic amino acid, negatively charged side chain), and L-isoleucine (hydrophobic amino acid, nonpolar) were selected as stabilizers, and the mixture of the three amino acids were optimized. The mixture had results comparative with albumin and other commonly used stabilizers showing good preservation of recombinant FVIII during lyophilization, robust stability with consistently high recovery of FVIIII, very low aggregate formation, and good storage stability without alterations in protein characteristics. In vivo test results showed that the efficacy was maintained and had no signs of toxicity. The study demonstrated that the three amino acid mixture acts as a good stabilizer for lyophilization of recombinant FVIII and as a safe excipient. PMID:23011837

Paik, Sang Hoon; Kim, Yong Jae; Han, Sang Kyul; Kim, Jean Man; Huh, Jae Wook; Park, Young In

2012-01-01

126

Polymer/organosilica nanocomposites based on polyimide with benzimidazole linkages and reactive organoclay containing isoleucine amino acid: Synthesis, characterization and morphology properties  

SciTech Connect

Highlights: ? A reactive organoclay was formed using L-isoleucine amino acid as a swelling agent. ? Polyimide was synthesized from benzimidazole diamine and pyromellitic dianhydride. ? Imide and benzimidazole groups assured the thermal stability of the nanocomposites. ? Nanocomposite films were prepared by an in situ polymerization reaction. ? The TEM micrographs of nanocomposites revealed well-exfoliated structures. -- Abstract: Polyimide–silica nanocomposites are attractive hybrid architectures that possess excellent mechanical, thermal and chemical properties. But, the dispersion of inorganic domains in the polymer matrix and the compatibility between the organic and inorganic phases are critical factors in these hybrid systems. In this investigation, a reactive organoclay was prepared via ion exchange reaction between protonated form of difunctional L-isoleucine amino acid as a swelling agent and Cloisite Na{sup +} montmorillonite. Amine functional groups of this swelling agent formed an ionic bond with the negatively charged silicates, whereas the remaining acid functional groups were available for further interaction with polymer chains. Then organo-soluble polyimide (PI) have been successfully synthesized from the reaction of 2-(3,5-diaminophenyl)-benzimidazole and pyromellitic dianhydride in N,N-dimethylacetamide. Finally, PI/organoclay nanocomposite films enclosing 1%, 3%, 5%, 7% and 10% of synthesized organoclay were successfully prepared by an in situ polymerization reaction through thermal imidization. The synthesized hybrid materials were subsequently characterized by Fourier transform infrared spectroscopy, X-ray diffraction, electron microscopy, and thermogravimetric analysis techniques. The PI/organoclay nanocomposite films have good optical transparencies and the mechanical properties were substantially improved by the incorporation of the reactive organoclay.

Mallakpour, Shadpour, E-mail: mallak@cc.iut.ac.ir [Organic Polymer Chemistry Research Laboratory, Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111, Islamic Republic of Iran (Iran, Islamic Republic of) [Organic Polymer Chemistry Research Laboratory, Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111, Islamic Republic of Iran (Iran, Islamic Republic of); Nanotechnology and Advanced Materials Institute, Isfahan University of Technology, Isfahan 84156-83111, Islamic Republic of Iran (Iran, Islamic Republic of); Dinari, Mohammad [Organic Polymer Chemistry Research Laboratory, Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111, Islamic Republic of Iran (Iran, Islamic Republic of)] [Organic Polymer Chemistry Research Laboratory, Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111, Islamic Republic of Iran (Iran, Islamic Republic of)

2012-09-15

127

1,25-Dihydroxyvitamin D3 Induces LL-37 and HBD-2 Production in Keratinocytes from Diabetic Foot Ulcers Promoting Wound Healing: An In Vitro Model  

PubMed Central

Diabetic foot ulcers (DFU) are one of the most common diabetes-related cause of hospitalization and often lead to severe infections and poor healing. It has been recently reported that patients with DFU have lower levels of antimicrobial peptides (AMPs) at the lesion area, which contributes with the impairment of wound healing. The aim of this study was to determine whether 1,25-dihydroxyvitamin D3 (1,25 (OH)2 D3) and L-isoleucine induced HBD-2 and LL-37 in primary cultures from DFU. We developed primary cell cultures from skin biopsies from 15 patients with DFU and 15 from healthy donors. Cultures were treated with 1,25 (OH)2D3 or L-isoleucine for 18 h. Keratinocytes phenotype was identified by western blot and flow cytometry. Real time qPCR for DEFB4, CAMP and VDR gene expression was performed as well as an ELISA to measure HBD-2 and LL-37 in supernatant. Antimicrobial activity, in vitro, wound healing and proliferation assays were performed with conditioned supernatant. The results show that primary culture from DFU treated with 1,25(OH)2D3, increased DEFB4 and CAMP gene expression and increased the production of HBD-2 and LL-37 in the culture supernatant. These supernatants had antimicrobial activity over E. coli and induced remarkable keratinocyte migration. In conclusion the 1,25(OH)2D3 restored the production of AMPs in primary cell from DFU which were capable to improve the in vitro wound healing assays, suggesting their potential therapeutic use on the treatment of DFU. PMID:25337708

Gonzalez-Curiel, Irma; Trujillo, Valentin; Montoya-Rosales, Alejandra; Rincon, Kublai; Rivas-Calderon, Bruno; deHaro-Acosta, Jeny; Marin-Luevano, Paulina; Lozano-Lopez, Daniel; Enciso-Moreno, Jose A.; Rivas-Santiago, Bruno

2014-01-01

128

Aroma-active ester profile of ale beer produced under different fermentation and nutritional conditions.  

PubMed

A broad range of aroma-active esters produced during fermentation are vital for the complex flavour of beer. This study assessed the influence of fermentation temperature, pH, and wort nutritional supplements on the production of yeast-derived ester compounds and the overall fermentation performance. The best fermentation performance was achieved when wort was supplemented with 0.75 g/l l-leucine resulting in highest reducing sugar and FAN (free amino nitrogen) utilization and ethanol production. At optimum fermentation pH of 5, 38.27% reducing sugars and 35.28% FAN was utilized resulting in 4.07% (v/v) ethanol. Wort supplemented with zinc sulphate (0.12 g/l) resulted in 5.01% ethanol (v/v) production and 54.32% reducing sugar utilization. Increase in fermentation temperature from 18°C to room temperature (± 22.5°C) resulted in 17.03% increased ethanol production and 14.42% and 62.82% increase in total acetate ester concentration and total ethyl ester concentration, respectively. Supplementation of worth with 0.12 g/l ZnSO4 resulted in 2.46-fold increase in both isoamyl acetate and ethyl decanoate concentration, while a 7.05-fold and 1.96-fold increase in the concentration of isoamyl acetate and ethyl decanoate, respectively was obtained upon 0.75 g/l l-leucine supplementation. Wort supplemented with l-leucine (0.75 g/l) yielded the highest beer foam head stability with a rating of 2.67, while highest yeast viability was achieved when wort was supplemented with 0.12 g/l zinc sulphate. Results from this study suggest that supplementing wort with essential nutrients required for yeast growth and optimizing the fermentation conditions could be an effective way of improving fermentation performance and controlling aroma-active esters in beer. PMID:23845914

Hiralal, Lettisha; Olaniran, Ademola O; Pillay, Balakrishna

2014-01-01

129

Cation-dependent nutrient transport in shrimp digestive tract.  

PubMed

Purified epithelial brush border membrane vesicles (BBMV) were produced from the hepatopancreas of the Atlantic White shrimp, Litopeneaus setiferus, using standard methods originally developed for mammalian tissues and previously applied to other crustacean and echinoderm epithelia. These vesicles were used to study the cation dependency of sugar and amino acid transport across luminal membranes of hepatopancreatic epithelial cells. (3)H-D: -glucose uptake by BBMV against transient sugar concentration gradients occurred when either transmembrane sodium or potassium gradients were the only driving forces for sugar accumulation, suggesting the presence of a possible coupled transport system capable of using either cation. (3)H-L: -histidine transport was only stimulated by a transmembrane potassium gradient, while (3)H-L: -leucine uptake was enhanced by either a sodium or potassium gradient. These responses suggest the possible presence of a potassium-dependent transporter that accommodates either amino acid and a sodium-dependent system restricted only to L: -leucine. Uptake of (3)H-L: -leucine was significantly stimulated (P < 0.05) by several metallic cations (e.g., Zn(2+), Cu(2+), Mn(2+), Cd(2+), or Co(2+)) at external pH values of 7.0 or 5.0 (internal pH 7.0), suggesting a potential synergistic role of the cations in the transmembrane transfer of amino acids. (3)H-L: -histidine influxes (15 suptakes) were hyperbolic functions of external [zinc] or [manganese], following Michaelis-Menten kinetics. The apparent affinity constant (e.g., K (m)) for manganese was an order of magnitude smaller (K (m) = 0.22 ?M Mn) than that for zinc (K (m) = 1.80 ?M Zn), while no significant difference (P > 0.05) occurred between their maximal transport velocities (e.g., J (max)). These results suggest that a number of cation-dependent nutrient transport systems occur on the shrimp brush border membrane and aid in the absorption of these important dietary elements. PMID:21983793

Simmons, Tamla; Mozo, Julie; Wilson, Jennifer; Ahearn, Gregory A

2012-02-01

130

Alpha-helical hydrophobic polypeptides form proton-selective channels in lipid bilayers.  

PubMed Central

Proton translocation is important in membrane-mediated processes such as ATP-dependent proton pumps, ATP synthesis, bacteriorhodopsin, and cytochrome oxidase function. The fundamental mechanism, however, is poorly understood. To test the theoretical possibility that bundles of hydrophobic alpha-helices could provide a low energy pathway for ion translocation through the lipid bilayer, polyamino acids were incorporated into extruded liposomes and planar lipid membranes, and proton translocation was measured. Liposomes with incorporated long-chain poly-L-alanine or poly-L-leucine were found to have proton permeability coefficients 5 to 7 times greater than control liposomes, whereas short-chain polyamino acids had relatively little effect. Potassium permeability was not increased markedly by any of the polyamino acids tested. Analytical thin layer chromatography measurements of lipid content and a fluorescamine assay for amino acids showed that there were approximately 135 polyleucine or 65 polyalanine molecules associated with each liposome. Fourier transform infrared spectroscopy indicated that a major fraction of the long-chain hydrophobic peptides existed in an alpha-helical conformation. Single-channel recording in both 0.1 N HCl and 0.1 M KCl was also used to determine whether proton-conducting channels formed in planar lipid membranes (phosphatidylcholine/phosphatidylethanolamine, 1:1). Poly-L-leucine and poly-L-alanine in HCl caused a 10- to 30-fold increase in frequency of conductive events compared to that seen in KCl or by the other polyamino acids in either solution. This finding correlates well with the liposome observations in which these two polyamino acids caused the largest increase in membrane proton permeability but had little effect on potassium permeability. Poly-L-leucine was considerably more conductive than poly-L-alanine due primarily to larger event amplitudes and, to a lesser extent, a higher event frequency. Poly-L-leucine caused two populations of conductive events, one in the 0.1-0.5 pA range, and one in the 1.0-5.0 pA range, whereas nearly all events caused by poly-L-alanine were in the 0.1-0.5 pA range at an applied voltage of +60 mV. The channel-like activity appeared to switch between conductive and nonconductive states, with most open-times in the range of 50-200 ms. We conclude that hydrophobic polyamino acids produce proton-conducting defects in lipid bilayers that may be used to model functional proton channels in biological membranes. Images FIGURE 13 PMID:7520289

Oliver, A E; Deamer, D W

1994-01-01

131

Initial Experience with the Radiotracer Anti1- Amino3-18F-Fluorocyclobutane-1Carboxylic Acid with PET\\/CT in Prostate Carcinoma  

Microsoft Academic Search

Conventional imaging techniques have serious limitations in the detection, staging, and restaging of prostate carcinoma. Anti- 1-amino-3-18F-fluorocyclobutane-1-carboxylicacid(anti-18F-FACBC) is a synthetic L-leucine analog that has excellent in vitro uptake within the DU-145 prostate carcinoma cell line and orthotopically implanted prostate tumor in nude rats. There is little renal excretion compared with 18F-FDG. The present study examines anti-18F-FACBC uptake in patients with

David M. Schuster; R. Votaw; Peter T. Nieh; Weiping Yu; A. Nye; Viraj Master; F. DuBois Bowman; Muta M. Issa; Mark M. Goodman

132

(L)- or (D)-valine tert-butylamide grafted on permethylated beta-cyclodextrin derivatives as new mixed binary chiral selectors: versatile tools for capillary gas chromatographic enantioseparation.  

PubMed

This work deals with the synthesis of two mixed binary chiral selectors prepared by grafting (L)- or (D)-valine tert-butylamide on permethylated cyclodextrin macrocycle. The enantioselective properties of the new chiral selectors diluted in OV11 polysiloxane (35% phenyl- and 65% methylsiloxane) were investigated by means of injections of 117 racemic mixtures. The mixed chiral selectors with (L)-valine and, to a lesser extent with (D)-valine, were found to have an improved enantioselectivity toward amino acid derivatives by comparison to permethylated cyclodextrin. The enantioseparation capability of these new chiral selectors has proven to be slightly less efficient than Chirasil-L-Val (Alltech) for amino acid derivatives, but it has been extended to include terpenes, lactones, esters, aliphatic compounds and aryl alcohols. PMID:19303600

Stephany, O; Dron, F; Tisse, S; Martinez, A; Nuzillard, J-M; Peulon-Agasse, V; Cardinaël, P; Bouillon, J-P

2009-05-01

133

Synthesis, structure, and magnetic properties of two 1-D helical coordination polymeric Cu(II) complexes  

NASA Astrophysics Data System (ADS)

Two helical coordination polymeric copper(II) complexes bearing amino acid Schiff bases HL or HL', which are condensed from 2-hydroxy-1-naphthaldehyde with 2-aminobenzoic acid or L-valine, respectively, have been prepared and characterised by X-ray crystallography. In [CuL] n ( 1) the copper(II) atoms are bridged by syn- anti carboxylate groups giving infinite 1-D right-handed helical chains which are further connected by weak C-H⋯Cu interactions to build a 2-D network. While in [CuL'] n ( 2) the carboxylate group acts as a rare monatomic bridge to connect the adjacent copper(II) atoms leading to the formation of a left-handed helical chain. Magnetic susceptibility measurements indicate that 1 exhibits weak ferromagnetic interactions whereas an antiferromagnetic coupling is established for 2. The magnetic behavior can be satisfactorily explained on the basis of the structural data.

Bian, He-Dong; Yang, Xiao-E.; Yu, Qing; Chen, Zi-Lu; Liang, Hong; Yan, Shi-Ping; Liao, Dai-Zheng

2008-01-01

134

The NRPS Enzyme DdaD Tethers N?-fumaramoyl-DAP for Fe(II)/?-ketoglutarate-Dependent Epoxidation by DdaC During Dapdiamide Antibiotic Biosynthesis  

PubMed Central

The gene cluster from Pantoea agglomerans responsible for biosynthesis of the dapdiamide antibiotics encodes an adenylation-thiolation didomain protein, DdaD, and an Fe(II)/?-ketoglutarate-dependent dioxygenase homolog, DdaC. Here we show that DdaD, a nonribosomal peptide synthetase module, activates and sequesters N?-fumaramoyl-L-2,3-diaminopropionic acid as a covalently tethered thioester for subsequent oxidative modification of the fumaramoyl group. DdaC catalyzes Fe(II)- and ?-ketoglutarate-dependent epoxidation of the covalently bound N?-fumaramoyl-L-2,3-diaminopropionyl-S-DdaD species to generate N?-epoxysuccinamoyl-DAP in thioester linkage to DdaD. After hydrolytic release, N?-epoxysuccinamoyl-DAP can be ligated to L-valine by the ATP-dependent ligase DdaF to form the natural antibiotic N?-epoxysuccinamoyl-diaminopropionyl-valine. PMID:20945916

Hollenhorst, Marie A.; Bumpus, Stefanie B.; Matthews, Megan L.; Bollinger, J. Martin; Kelleher, Neil L.; Walsh, Christopher T.

2010-01-01

135

mer-Hydridotris(tri­methyl­phosphane-?P)(d-valinato-?2 N,O)iridium hexa­fluorido­phosphate di­chloro­methane 0.675-solvate  

PubMed Central

The title compound, [Ir(C5H10NO2)H(C3H9P)3]PF6·0.675CH2Cl2, an iridium compound with a meridional arrangement of PMe3 groups, O,N-bidentate coordination of d-valine and with a hydride ligand trans to the N atom is compared with the l-valine complex reported previously. As expected, the complexes from the corresponding l and d isomers of valine crystallize in enanti­omorphic space groups (P43 and P41, respectively). In the crystal, N—H?O and N—H?F hydrogen bonding is observed, the N—H to carbonyl oxygen hydrogen bond producing a helical motif that proceeds along the 41 screw of the c axis. PMID:24764947

Merola, Joseph S.; Slebodnick, Carla; Berg, Michael; Ritchie, Melissa K.

2014-01-01

136

Analysis of the Effects of a gerP Mutation on the Germination of Spores of Bacillus subtilis  

PubMed Central

As previously reported, gerP Bacillus subtilis spores were defective in nutrient germination triggered via various germinant receptors (GRs), and the defect was eliminated by severe spore coat defects. The gerP spores' GR-dependent germination had a longer lag time between addition of germinants and initiation of rapid release of spores' dipicolinic acid (DPA), but times for release of >90% of DPA from individual spores were identical for wild-type and gerP spores. The gerP spores were also defective in GR-independent germination by DPA with its associated Ca2+ divalent cation (CaDPA) but germinated better than wild-type spores with the GR-independent germinant dodecylamine. The gerP spores exhibited no increased sensitivity to hypochlorite, suggesting that these spores have no significant coat defect. Overexpression of GRs in gerP spores did lead to faster germination via the overexpressed GR, but this was still slower than germination of comparable gerP+ spores. Unlike wild-type spores, for which maximal nutrient germinant concentrations were between 500 ?M and 2 mM for l-alanine and ?10 mM for l-valine, rates of gerP spore germination increased up to between 200 mM and 1 M l-alanine and 100 mM l-valine, and at 1 M l-alanine, the rates of germination of wild-type and gerP spores with or without all alanine racemases were almost identical. A high pressure of 150 MPa that triggers spore germination by activating GRs also triggered germination of wild-type and gerP spores identically. All these results support the suggestion that GerP proteins facilitate access of nutrient germinants to their cognate GRs in spores' inner membrane. PMID:22904285

Butzin, Xuan Yi; Troiano, Anthony J.; Coleman, William H.; Griffiths, Keren K.; Doona, Christopher J.; Feeherry, Florence E.; Wang, Guiwen; Li, Yong-qing

2012-01-01

137

Metabolism As a Function of Water Potential in Air-Dry Seeds of Charlock (Sinapis arvensis L.).  

PubMed

A new method is described for studying the metabolism of air-dry seeds. An initial pulse of (14)CO(2) was supplied to seeds maintained in air at controlled low water potentials for 6 months. Seeds were also infiltrated with 2-(14)C-acetate and with (14)C-l-leucine at 0 C, redried rapidly at 0 C, and maintained at controlled low water potentials for 4 to 6 weeks. The metabolism of the air-dry seeds was a function of the water content of the tissues, which was in equilibrium with the water potential at the seed surface. The fixation of (14)CO(2) and the utilization of 2-(14)C-acetate increased exponentially with water content. The incorporation of (14)C-l-leucine into protein increased linearly with water content. Metabolism was not reduced to a low rate except in air-dry seeds at the lowest water potentials (-1716 to -762 bars) with 4 to 6% water. PMID:16659654

Edwards, M

1976-08-01

138

Aerosolization Characteristics of Dry Powder Inhaler Formulations for the Excipient Enhanced Growth (EEG) Application: Effect of Spray Drying Process Conditions on Aerosol Performance  

PubMed Central

The aim of this study was to develop a spray dried submicrometer powder formulation suitable for the excipient enhanced growth (EEG) application. Combination particles were prepared using the Buchi Nano spray dryer B-90. A number of spray drying and formulation variables were investigated with the aims of producing dry powder formulations that were readily dispersed upon aerosolization and maximizing the fraction of submicrometer particles. Albuterol sulfate, mannitol, L-leucine, and poloxamer 188 were selected as a model drug, hygroscopic excipient, dispersibility enhancer and surfactant, respectively. Formulations were assessed by scanning electron microscopy and aerosol performance following aerosolization using an Aerolizer® dry powder inhaler (DPI). In vitro drug deposition was studied using a realistic mouth-throat (MT) model. Based on the in vitro aerosolization results, the best performing submicrometer powder formulation consisted of albuterol sulfate, mannitol, L-leucine and poloxamer 188 in a ratio of 30:48:20:2, containing 0.5% solids in a water:ethanol (80:20% v/v) solution which was spray dried at 70 °C. The submicrometer particle fraction (FPF1?m/ED) of this final formulation was 28.3% with more than 80% of the capsule contents being emitted during aerosolization. This formulation also showed 4.1% MT deposition. The developed combination formulation delivered a powder aerosol developed for the EEG application with high dispersion efficiency and low MT deposition from a convenient DPI device platform. PMID:23313343

Son, Yoen-Ju; Longest, P. Worth; Hindle, Michael

2013-01-01

139

JPH203, an L-type amino acid transporter 1-selective compound, induces apoptosis of YD-38 human oral cancer cells.  

PubMed

Compared to most normal cells that express L-type amino acid transporter 2, L-type amino acid transporter 1 is highly expressed in cancer cells and presumed to support their elevated growth and proliferation. This study examined JPH203, a potent and selective L-type amino acid transporter 1 inhibitor, and its ability to suppress YD-38 human oral cancer cell growth. The YD-38 cells express L-type amino acid transporter 1 with its associating protein 4F2 heavy chain, but not L-type amino acid transporter 2. JPH203 and BCH, a non-selective L-type amino acid transporter inhibitor, completely inhibited l-leucine uptake in YD-38 cells. As expected, the intrinsic affinity of JPH203 to inhibit l-leucine uptake was far more efficient than BCH. Likewise, JPH203 and BCH inhibited YD-38 cell growth, with JPH203 being superior to BCH. JPH203 up-regulated the population of apoptotic YD-38 cells through the activation of apoptotic factors, including caspases and PARP. These results suggest that the inhibition of L-type amino acid transporter 1 activity via JPH203, which may act as a potential novel anti-oral-cancer agent, leads to apoptosis by inducing the intracellular depletion of the neutral amino acids essential for cancer cell growth in YD-38 human oral cancer cells. PMID:24492461

Yun, Dae-Woong; Lee, Seul Ah; Park, Min-Gyeong; Kim, Jae-Sung; Yu, Sun-Kyoung; Park, Mi-Ra; Kim, Su-Gwan; Oh, Ji-Su; Kim, Chun Sung; Kim, Heung-Joong; Kim, Jin-Soo; Chun, Hong Sung; Kanai, Yoshikatsu; Endou, Hitoshi; Wempe, Michael F; Kim, Do Kyung

2014-01-01

140

Use of membrane vesicles to estimate the numbers of system y+ and system L amino acid transporters in human erythrocytes.  

PubMed Central

We have used equilibrium values for L-leucine and L-lysine uptake by right-side-out vesicles to estimate the membrane abundance (sites/cell) of Na(+)-dependent amino acid transport systems L and y+ in human erythrocytes. All of the intravesicular space was accessible to L-leucine, as judged by comparisons with uridine uptake via the equilibrative nucleoside transporter (10(4) sites/cell). In contrast, only 28% of the total intravesicular space was accessible to L-lysine uptake via system y+. Since human erythrocyte membranes generate an average of approximately 1000 vesicles/cell, these data provide evidence that system L is a relatively high-abundance membrane transport protein in human erythrocytes, while system y+ is present in smaller amounts (approximately 300 copies/cell). Calculated turnover numbers for L-lysine transport by system y+ at 37 degrees C are 24 s-1 for zero-trans influx and 150 s-1 for equilibrium-exchange influx. PMID:1907132

Tse, C M; Fincham, D A; Ellory, J C; Young, J D

1991-01-01

141

Effects of disintegration-promoting agent, lubricants and moisture treatment on optimized fast disintegrating tablets.  

PubMed

Effects of calcium silicate (disintegration-promoting agent) and various lubricants on an optimized beta-cyclodextrin-based fast-disintegrating tablet formulation were investigated. Effects of moisture treatment were also evaluated at 75, 85 and 95% relative humidities. A two factor, three levels (3(2)) full factorial design was used to optimize concentrations of calcium silicate and lubricant. Magnesium stearate, being commonly used lubricant, was used to optimize lubricant concentration in optimization study. Other lubricants were evaluated at an obtained optimum concentration. Desiccator with saturated salt solutions was used to analyze effects of moisture treatments. Results of multiple linear regression analysis revealed that concentration of calcium silicate had no effect; however concentration of lubricant was found to be important for tablet disintegration and hardness. An optimized value of 1.5% of magnesium stearate gave disintegration time of 23.4 s and hardness of 1.42 kg. At an optimized concentration, glycerol dibehenate and L-leucine significantly affected disintegration time, while talc and stearic acid had no significant effect. Tablet hardness was significantly affected with L-leucine, while other lubricants had no significant effect. Hardness was not affected at 75% moisture treatment. Moisture treatment at 85 and 95% increased hardness of the tablets; however at the same time it negatively affected the disintegration time. PMID:18778759

Late, Sameer G; Yu, Yi-Ying; Banga, Ajay K

2009-01-01

142

Crystal Structure of a Novel N-Substituted L-Amino Acid Dioxygenase from Burkholderia ambifaria AMMD  

PubMed Central

A novel dioxygenase from Burkholderia ambifaria AMMD (SadA) stereoselectively catalyzes the C3-hydroxylation of N-substituted branched-chain or aromatic L-amino acids, especially N-succinyl-L-leucine, coupled with the conversion of ?-ketoglutarate to succinate and CO2. To elucidate the structural basis of the substrate specificity and stereoselective hydroxylation, we determined the crystal structures of the SadA.Zn(II) and SadA.Zn(II).?-KG complexes at 1.77 Å and 1.98 Å resolutions, respectively. SadA adopted a double-stranded ?-helix fold at the core of the structure. In addition, an HXD/EXnH motif in the active site coordinated a Zn(II) as a substitute for Fe(II). The ?-KG molecule also coordinated Zn(II) in a bidentate manner via its 1-carboxylate and 2-oxo groups. Based on the SadA.Zn(II).?-KG structure and mutation analyses, we constructed substrate-binding models with N-succinyl-L-leucine and N-succinyl-L-phenylalanine, which provided new insight into the substrate specificity. The results will be useful for the rational design of SadA variants aimed at the recognition of various N-succinyl L-amino acids. PMID:23724013

Qin, Hui-Min; Miyakawa, Takuya; Jia, Min Ze; Nakamura, Akira; Ohtsuka, Jun; Xue, You-Lin; Kawashima, Takashi; Kasahara, Takuya; Hibi, Makoto; Ogawa, Jun; Tanokura, Masaru

2013-01-01

143

Radioactive contamination of the marine environment: Uptake and distribution of3H in Dunaliella bioculata  

NASA Astrophysics Data System (ADS)

The marine flagellate Dunaliella bioculata, which is easily cultivated under laboratory conditions, is a suitable organism for assessing the importance of the radioactive contamination by3H bound to organic molecules. We have studied the uptake of the following tritiated precursors: thymidine-methyl-3H, adenine-2-3H, uridine-5-3H, l-leucine-4-3H, glycine-2-3H, l-arginine-3.4-3H, 1-aspartic acid-2. 3-3H, 1-phenylalanine-2.3-3H, D-glucose-2-3H and D-glucose-6-3H. Under the experimental conditions (2000 lux; incubation time 30 min), all tritiated molecules are taken up by D. bioculata. Their intracellular concentration may reach that of the external medium. However, leucine and adenine accumulate in the algae: their respective concentrations are 10 and 100 times higher than in the culture medium. The molecular distribution of3H has been studied by various biochemical techniques and by sieve chromatography on sepharose 4B. It has been found that more l-leucine-4-3H is incorporated into acid and acetone soluble substances than into proteins. Adenine-2-3H is mainly incorporated into macromolecules of biological significance (RNA, DNA). CsCl gradient centrifugation has shown that the total DNA of Dunaliella is constituted by a major (?=1.707 g/cm3) and by a minor (?=1.693 g/cm3) component.

Strack, S.; Bonotto, S.; Kirchmann, R.

1980-03-01

144

/sup 3/H-cyclosporine internalization and secretion by human fetal pancreatic islets  

SciTech Connect

Human fetal pancreatic islets were isolated from 16- to 20-week-old fetuses by a collagenase technique and cultured 48 hr in RPMI 1640 containing 10% human adult serum and unlabeled 0 to 5 micrograms cyclosporine A (CsA)/ml. Insulin secretory capacity of human fetal islets was expressed as a fractional stimulatory ratio FSR = F2/F1 of the fractional secretion rates during two successive 1 hr static incubations first with 2 mM glucose (F1) to stabilize secretion followed by maximal stimulus, i.e., 25 mM glucose plus 10 mM L-leucine and 10 mM L-arginine (F2). Unlabeled CsA at the above concentrations had no significant effects on the insulin secretory capacity expressed by FSR-values. Studies of net uptake of 3H-CsA by islets cultured for varying periods up to 40 hr and expressed as picomole 3H-CsA per picomole islet insulin content demonstrated that uptake rate was slow and did not reach isotopic equilibrium over the 40 hr of culture. When isolated fetal islets were cultured for 48 hr in the presence of 3H-CsA and varying concentrations of unlabeled CsA it was found during two successive 1 hr static incubations that fetal islets secrete insulin concomitantly with 3H-CsA following maximal stimulus for secretion. An optimal secretory molar ratio of 3H-CsA to insulin of 4.0 +/- 1.3 (n = 7) was found after islets were cultured 48 hr in the presence of a saturating 2.128 micrograms 3H-CsA per milliliter culture medium. In three successive 30-min static incubations of 3H-CsA loaded islets, first with low glucose, followed by high glucose plus L-arginine and L-leucine, and finally with high glucose plus L-arginine and L-leucine and 10 mM theophylline, the proportional fractional secretion rates of insulin and 3H-CsA were of the same magnitude.

Formby, B.; Walker, L.; Peterson, C.M.

1988-10-01

145

Jasmonate perception by inositol-phosphate-potentiated COI1?JAZ co-receptor  

SciTech Connect

Jasmonates are a family of plant hormones that regulate plant growth, development and responses to stress. The F-box protein CORONATINE INSENSITIVE 1 (COI1) mediates jasmonate signalling by promoting hormone-dependent ubiquitylation and degradation of transcriptional repressor JAZ proteins. Despite its importance, the mechanism of jasmonate perception remains unclear. Here we present structural and pharmacological data to show that the true Arabidopsis jasmonate receptor is a complex of both COI1 and JAZ. COI1 contains an open pocket that recognizes the bioactive hormone (3R,7S)-jasmonoyl-l-isoleucine (JA-Ile) with high specificity. High-affinity hormone binding requires a bipartite JAZ degron sequence consisting of a conserved {alpha}-helix for COI1 docking and a loop region to trap the hormone in its binding pocket. In addition, we identify a third critical component of the jasmonate co-receptor complex, inositol pentakisphosphate, which interacts with both COI1 and JAZ adjacent to the ligand. Our results unravel the mechanism of jasmonate perception and highlight the ability of F-box proteins to evolve as multi-component signalling hubs.

Sheard, Laura B.; Tan, Xu; Mao, Haibin; Withers, John; Ben-Nissan, Gili; Hinds, Thomas R.; Kobayashi, Yuichi; Hsu, Fong-Fu; Sharon, Michal; Browse, John; He, Sheng Yang; Rizo, Josep; Howe, Gregg A.; Zheng, Ning (Tokyo Inst. Tech.); (UWASH); (MSU); (WIS-I); (WU-MED); (UTSMC)

2011-11-07

146

The Amidohydrolases IAR3 and ILL6 Contribute to Jasmonoyl-Isoleucine Hormone Turnover and Generate 12-Hydroxyjasmonic Acid Upon Wounding in Arabidopsis Leaves*  

PubMed Central

Jasmonates (JAs) are a class of signaling compounds that mediate complex developmental and adaptative responses in plants. JAs derive from jasmonic acid (JA) through various enzymatic modifications, including conjugation to amino acids or oxidation, yielding an array of derivatives. The main hormonal signal, jasmonoyl-l-isoleucine (JA-Ile), has been found recently to undergo catabolic inactivation by cytochrome P450-mediated oxidation. We characterize here two amidohydrolases, IAR3 and ILL6, that define a second pathway for JA-Ile turnover during the wound response in Arabidopsis leaves. Biochemical and genetic evidence indicates that these two enzymes cleave the JA-Ile signal, but act also on the 12OH-JA-Ile conjugate. We also show that unexpectedly, the abundant accumulation of tuberonic acid (12OH-JA) after wounding originates partly through a sequential pathway involving (i) conjugation of JA to Ile, (ii) oxidation of the JA-Ile conjugate, and (iii) cleavage under the action of the amidohydrolases. The coordinated actions of oxidative and hydrolytic branches in the jasmonate pathway highlight novel mechanisms of JA-Ile hormone turnover and redefine the dynamic metabolic grid of jasmonate conversion in the wound response. PMID:24052260

Widemann, Emilie; Miesch, Laurence; Lugan, Raphaël; Holder, Emilie; Heinrich, Clément; Aubert, Yann; Miesch, Michel; Pinot, Franck; Heitz, Thierry

2013-01-01

147

Biosynthesis of the defensive alkaloid cicindeloine in Stenus solutus beetles  

NASA Astrophysics Data System (ADS)

To protect themselves from predation and microorganismic infestation, rove beetles of the genus Stenus produce and store bioactive alkaloids like stenusine, 3-(2-methyl-1-butenyl)pyridine, and cicindeloine in their pygidial glands. The biosynthesis of stenusine and 3-(2-methyl-1-butenyl)pyridine was previously investigated in Stenus bimaculatus and Stenus similis, respectively. Both molecules follow the same biosynthetic pathway, where the N-heterocyclic ring is derived from l-lysine and the side chain from l-isoleucine. The different alkaloids are finally obtained by slight modifications of shared precursor molecules. The piperideine alkaloid cicindeloine occurs as a main compound additionally to ( E)-3-(2-methyl-1-butenyl)pyridine and traces of stenusine in the pygidial gland secretion of Stenus cicindeloides and Stenus solutus. Feeding of S. solutus beetles with [D,15N]-labeled amino acids followed by GC/MS analysis techniques showed that cicindeloine is synthesized via the identical pathway and precursor molecules as the other two defensive alkaloids.

Schierling, Andreas; Dettner, Konrad; Schmidt, Jürgen; Seifert, Karlheinz

2012-08-01

148

Accurate measurements of 13C-13C distances in uniformly 13C-labeled proteins using multi-dimensional four-oscillating field solid-state NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Application of sets of 13C-13C internuclear distance restraints constitutes a typical key element in determining the structure of peptides and proteins by magic-angle-spinning solid-state NMR spectroscopy. Accurate measurements of the structurally highly important 13C-13C distances in uniformly 13C-labeled peptides and proteins, however, pose a big challenge due to the problem of dipolar truncation. Here, we present novel two-dimensional (2D) solid-state NMR experiments capable of extracting distances between carbonyl (13C') and aliphatic (13Caliphatic) spins with high accuracy. The method is based on an improved version of the four-oscillating field (FOLD) technique [L. A. Straasø, M. Bjerring, N. Khaneja, and N. C. Nielsen, J. Chem. Phys. 130, 225103 (2009)] which circumvents the problem of dipolar truncation, thereby offering a base for accurate extraction of internuclear distances in many-spin systems. The ability to extract reliable accurate distances is demonstrated using one- and two-dimensional variants of the FOLD experiment on uniformly 13C,15N-labeled-L-isoleucine. In a more challenging biological application, FOLD 2D experiments are used to determine a large number of 13C'-13Caliphatic distances in amyloid fibrils formed by the SNNFGAILSS fibrillating core of the human islet amyloid polypeptide with uniform 13C,15N-labeling on the FGAIL fragment.

Straasø, Lasse Arnt; Nielsen, Jakob Toudahl; Bjerring, Morten; Khaneja, Navin; Nielsen, Niels Chr.

2014-09-01

149

Thermosensitive/magnetic poly(organophosphazene) hydrogel as a long-term magnetic resonance contrast platform.  

PubMed

A thermosensitive/magnetic poly(organophosphazene) hydrogel (a magnetic hydrogel) was designed and synthesized for long-term magnetic resonance (MR) imaging. To turn a thermosensitive poly(organophosphazene) hydrogel (an original hydrogel) into a long-term MR contrast platform, cobalt ferrite (CoFe(2)O(4)) nanoparticles, which have hydrophobic surfaces, were bound to the original hydrogel via interactions between the hydrophobic surfaces of the nanoparticles and the (L)-isoleucine ethyl esters of the polymer. The magnetic hydrogel showed extremely low cytotoxicity and adequate magnetic properties for use in long-term MR imaging, in addition to possessing the same properties of the original hydrogel, such as viscosity, thermosensitivity, biodegradability, biocompatibility, a reversible sol-to-gel phase transition near body temperature, and injectability. The magnetic hydrogel was injected into a rat brain using stereotactic surgery. After the injection, the applicable potentiality as a long-term MR contrast platform was successfully estimated over 4-5 weeks. Consequently, it was shown that a magnetic hydrogel as a long-term MR contrast platform has the potential to be applied in a long-term theranostic hydrogel system. Furthermore, it is expected that this platform can be useful in the clinical field of incurable diseases due to either surgical difficulties or lethality, such as with brain tumors, when the platform is combined with therapeutic drugs for long-term MR theragnosis in further studies. PMID:21975461

Kim, Jang Il; Chun, ChangJu; Kim, Bora; Hong, Ji Min; Cho, Jung-Kyo; Lee, Seung Hoon; Song, Soo-Chang

2012-01-01

150

Synthesis, Characterization, and Antibacterial Studies of Mixed Ligand Dioxouranium Complexes with 8-Hydroxyquinoline and Some Amino Acids  

PubMed Central

Mixed ligand complexes of dioxouranium (VI) of the type [UO2(Q)(L)·2H2O] have been synthesized using 8-hydroxyquinoline (HQ) as a primary ligand and amino acids (HL) such as L-threonine, L-tryptophan, and L-isoleucine as secondary ligands. The metal complexes have been characterized by elemental analysis, electrical conductance, magnetic susceptibility measurements, and spectral and thermal studies. The electrical conductance studies of the complexes indicate their nonelectrolytic nature. Magnetic susceptibility measurements revealed diamagnetic nature of the complexes. Electronic absorption spectra of the complexes show intraligand and charge transfer transitions, respectively. Bonding of the metal ion through N- and O-donor atoms of the ligands is revealed by IR studies, and the chemical environment of the protons is confirmed by NMR studies. The thermal analysis data of the complexes indicate the presence of coordinated water molecules. The agar cup and tube dilution methods have been used to study the antibacterial activity of the complexes against the pathogenic bacteria S. aureus, C. diphtheriae, S. typhi, and E. coli. PMID:22389843

Patil, Sunil S.; Thakur, Ganesh A.; Shaikh, Manzoor M.

2011-01-01

151

A novel extracellular cyclic lipopeptide which promotes flagellum-dependent and -independent spreading growth of Serratia marcescens.  

PubMed Central

Serrawettin W2, a surface-active exolipid produced by nonpigmented Serratia marcescens NS 25, was examined for its chemical structure and physiological functions. The chemical structure was determined by degradation analyses, infrared spectroscopy, mass spectrometry, and proton magnetic resonance spectroscopy. Serrawettin W2 was shown to be a novel cyclodepsipeptide containing a fatty acid (3-hydroxydecanoic acid) and five amino acids. The peptide was proposed to be D-leucine (N-bonded to the carboxylate of the fatty acid)-L-serine-L-threonine-D-phenylalanine-L-isoleucine (bonded to the 3-hydroxyl group). By examining the effects of isolated serrawettin W2 on serrawettinless mutants, this lipopeptide was shown to be active in the promotion of flagellum-independent spreading growth of the bacteria on a hard agar surface. The parent strain NS 25 formed a giant colony with a self-similar characteristic after incubation for a relatively long time (1 to 2 weeks), similar to other fractal colony-producing strains of S. marcescens (producers of the different serrawettins W1 and W3). On a semisolid medium that permitted flagellum-dependent spreading growth, an external supply of serrawettin W2 accelerated surface translocation of a serrawettinless mutant during a short period (12 h) of observation. In contrast, bacterial translocation in the subsurface space of the semisolid agar was not enhanced by serrawettins. Thus, the extracellular lipids seem to contribute specifically to the surface translocation of the bacteria by exhibiting surfactant activity. Images PMID:1548227

Matsuyama, T; Kaneda, K; Nakagawa, Y; Isa, K; Hara-Hotta, H; Yano, I

1992-01-01

152

Chiral speciation and determination of DL-selenomethionine enantiomers on a novel chiral ligand-exchange stationary phase.  

PubMed

A new type of chiral ligand-exchange stationary phase (CLES) was successfully synthesized by treating silica gel with beta-(3,4-epoxycyclohexyl)ethyltrimethoxy silane and opening the epoxy ring by L-isoleucine. The chiral speciation of DL-selenomethionine (DL-SeMet) by high-performance liquid chromatography (HPLC) with UV absorbance on the CLES column was studied. The influences of the contents of copper ion and methanol as well as the pH value in the mobile phase and temperature of the column on the efficiency of resolution of DL-SeMet were investigated in detail. DL-SeMet could be completely resolved within 40 min under the optimal operating conditions of 0.1 mmol/L Cu2+ at 0.05 mol/L KH2PO4 buffer (pH = 5.5) and 35 degrees C temperature of the column. The limits of detection of D- and L-SeMet were 255 ppb and 286 ppb, respectively. This method was applied to determine the D- and L-enantiomers of DL-SeMet in real samples, such as selenized yeast powder and garlic. PMID:15790108

Huang, Xiaojia; Wang, Junde; Wang, Qiuquan; Huang, Benli

2005-03-01

153

Hepatic and Fecal Metabolomic Analysis of the Effects of Lactobacillus rhamnosus GG on Alcoholic Fatty Liver Disease in Mice.  

PubMed

The interactions among the gut, liver, and immune system play an important role in liver disease. Probiotics have been used for the treatment and prevention of many pathological conditions, including liver diseases. Comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOF MS) was used herein, in conjunction with chemometric data analysis, to identify metabolites significantly affected by probiotics in mice fed with or without alcohol. The metabolomics analysis indicates that the levels of fatty acids increased in mouse liver and decreased in mouse feces when mice were chronically exposed to alcohol. Supplementing the alcohol-fed mice with culture supernatant from Lactobacillus rhamnosus GG (LGGs) normalized these alcohol-induced abnormalities and prevented alcoholic liver disease (ALD). These results agree well with previous studies. In addition to diet-derived long chain fatty acids (LCFAs), LGGs may positively modify the gut's bacterial population to stimulate LCFA synthesis, which has been shown to enhance intestinal barrier function, reduce endotoxemia, and prevent ALD. We also found that several amino acids, including l-isoleucine, a branched chain amino acid, were downregulated in the liver and fecal samples from animals exposed to alcohol and that the levels of these amino acids were corrected by LGGs. These results demonstrate that LGGs alleviates alcohol-induced fatty liver by mechanisms involving increasing intestinal and decreasing hepatic fatty acids and increasing amino acid concentration. PMID:25592873

Shi, Xue; Wei, Xiaoli; Yin, Xinmin; Wang, Yuhua; Zhang, Min; Zhao, Cuiqing; Zhao, Haiyang; McClain, Craig J; Feng, Wenke; Zhang, Xiang

2015-02-01

154

Rational design of a ligand-based antagonist of jasmonate perception.  

PubMed

(+)-7-iso-Jasmonoyl-L-isoleucine (JA-Ile) regulates developmental and stress responses in plants. Its perception involves the formation of a ternary complex with the F-box COI1 and a member of the JAZ family of co-repressors and leads to JAZ degradation. Coronatine (COR) is a bacterial phytotoxin that functionally mimics JA-Ile and interacts with the COI1-JAZ co-receptor with higher affinity than JA-Ile. On the basis of the co-receptor structure, we designed ligand derivatives that spatially impede the interaction of the co-receptor proteins and, therefore, should act as competitive antagonists. One derivative, coronatine-O-methyloxime (COR-MO), has strong activity in preventing the COI1-JAZ interaction, JAZ degradation and the effects of JA-Ile or COR on several JA-mediated responses in Arabidopsis thaliana. Moreover, it potentiates plant resistance, preventing the effect of bacterially produced COR during Pseudomonas syringae infections in different plant species. In addition to the utility of COR-MO for plant biology research, our results underscore its biotechnological potential for safer and sustainable agriculture. PMID:24997606

Monte, Isabel; Hamberg, Mats; Chini, Andrea; Gimenez-Ibanez, Selena; García-Casado, Gloria; Porzel, Andrea; Pazos, Florencio; Boter, Marta; Solano, Roberto

2014-08-01

155

A high-throughput multivariate optimization for the simultaneous enantioseparation and detection of barbiturates in micellar electrokinetic chromatography-mass spectrometry (MEKC-MS)  

PubMed Central

The R- and S-configurations of barbiturates display differences in potency and biological activity. In this study, multivariate micellar electrokinetic chromatography-mass spectrometry (MEKC-MS) approach for the simultaneous analysis of three chiral barbiturates (mephobarbital, pentobarbital, and secobarbital) is developed using a polymeric chiral surfactant. After screening eleven amino acid polymeric surfactants, polysodium N-undecenoxycarbonyl-L-isoleucinate (poly-L-SUCIL) was found to be the best chiral selector. The multivariate central composite design (CCD) is used to optimize the chiral resolution, decrease the total analysis time, and improve the ESI-MS signal-to-noise (S/N) ratio. In the preliminary set of experiments, the ranges of the factors investigated in the multivariate approaches are determined. Next, the CCD design is conducted to determine the best overall chiral resolution with shortest possible run times. This optimization resulted in simultaneous enantioseparation in less than 32 minutes of all three barbiturates with 3–5 fold higher sensitivity by MS compared to UV detection. The adequacy of the multivariate model is validated by three replicate experimental runs at the predicted optimum conditions. The predicted results of MEKC-MS are found to be in good agreement with the experimental data for migration times, resolution and S/N ratio. The optimized method provided good results in terms of linearity and recovery values of chiral barbiturates spiked in human serum after solid phase extraction procedure. PMID:20819283

Wang, Bin; He, Jun; Shamsi, Shahab A.

2011-01-01

156

Purification and properties of aldehyde dehydrogenase from Proteus vulgaris.  

PubMed

NADP-linked aldehyde dehydrogenase (aldehyde : NADP+ oxidoreductase, EC 1.2.1.4) was purified from Proteus vulgaris to the stage of homogeneity as judged by ultracentrifugation and polyacrylamide gel electrophoresis. The molecular weight of the purified enzyme was estimated to be 130000 by gel filtration. The enzyme which was crystallized from ammonium sulfate solution, lost its activity. The enzyme did not require coenzyme A, and the reaction was completely dependent on ammonium ions which could be partially replaced by Rb+ or K+. The optimum pH was about 9. Broad substrate specificity was observed and Km values for propionaldehyde, acetaldehyde and isovaleraldehyde were 1.7 - 10(-5), 4 - 10(-5) and 3 - 10(-5) M, respectively. The physiological role of the enzyme in living cells is obscure, but might account for another degradative pathway of L-leucine in P. vulgaris differing from the established pathway. PMID:13839

Sugawara, Y; Sasaki, S

1977-02-01

157

Descending pathways to the cutaneus trunci muscle motoneuronal cell group in the cat  

NASA Technical Reports Server (NTRS)

Pathways involved in the cutaneous trunci muscle (CTM) reflex in the cat were investigated. Experimental animals were injected with tritium-labeled L-leucine into their spinal cord, brain stem, or diencephalon and, after six weeks, perfused with 10-percent formalin. The brains and spinal cords were postfixed in formalin and were cut into transverse 25-micron-thick frozen sections for autoradiography. Results based on injections in the C1, C2, C6, and C8 segments suggest that propriospinal pathways to the CTM motor nucleus originating in the cervical cord do no exist, although these propriospinal projections are very strong to all other motoneuronal cell groups surrounding the CTM motor nucleus. The results also demonstrate presence of specific supraspinal projections to the CTM motor nucleus, originating in the contralateral nucleus retroambiguous and the ipsilateral dorsolateral pontine tegmentum.

Holstege, Gert; Blok, Bertil F.

1989-01-01

158

High-level expression and characterization of carboxypeptidase Y from Saccharomyces cerevisiae in Pichia pastoris GS115.  

PubMed

Carboxypeptidase Y is widely used in peptide sequencing and mass spectrometry. PRC1 coding for proteinase C from Saccharomyces cerevisiae was expressed in Pichia pastoris GS115 as procarboxypeptidase Y with a yield of ~605 mg/l in shake-flasks after 168 h induction with 1 % (v/v) methanol. This precursor of carboxypeptidase Y was cleaved by endogenous proteinases of P. pastoris and released into the fermentation broth as active carboxypeptidase Y within 2 weeks at 10 °C, which facilitated the preparation of mature carboxypeptidase Y. The recombinant enzyme was purified. It was optimally active at 30 °C and pH 6.0, with an optimal activity of ~305 U/mg using benzyloxycarbonyl-L-phenylalanyl-L-leucine as substrate. This is the first report about high-level expression and activation of carboxypeptidase Y in P. pastoris. PMID:25214228

Yu, Xianhong; Zhai, Chao; Zhong, Xing; Tang, Wei; Wang, Xiaojuan; Yang, Hu; Chen, Wanping; Ma, Lixin

2014-09-12

159

Multivariate approach for the enantioselective analysis in micellar electrokinetic chromatography-mass spectrometry. I. Simultaneous optimization of binaphthyl derivatives in negative ion mode.  

PubMed

A mixture of two molecular micelles polysodium N-undecenoxy carbonyl-L-leucinate, (poly-L-SUCL) and polysodium N-undecanoyl leucylvalinate, (poly-L-SULV) was utilized in micellar electrokinetic chromatography-electrospray ionization-mass spectrometry (MEKC-ESI-MS) to simultaneously separate and detect enantiomers of binaphthyl derivatives. Separation parameters such as background buffer composition, voltage, temperature, and nebulizer pressure were optimized using a multivariate central composite design (CCD). Baseline enantioseparation for both analytes was achieved. The CCD was also used in the optimization of sheath liquid and spray chamber parameters to achieve optimum ESI-MS response. The results demonstrate that CCD is a powerful tool for the optimization of MEKC-MS parameters and the response surface model analysis can provide in-depth statistical understandings of the significant factors required to achieve maximum enantioresolution and ESI-MS sensitivity. PMID:19110258

He, Jun; Shamsi, Shahab A

2009-01-30

160

The involvement of opioid peptides in stress-induced analgesia in the slug Arion ater.  

PubMed

Application of tail-pinch stress to the terrestrial slug, Arion ater, produced a significant increase in the response time when tested on the hot-plate for foot-lifting response. The analgesia was completely reversed by injections of the opiate antagonists, naltrexone and ICI 174864, in a dose-dependent manner. Analgesia could also be elicited by the injection into the foot of beta-endorphin and the enkephalin analogues, DAGO and DADLE. No effect was seen with dynorphin A (1-8) or dynorphin A (1-17). The stress-induced analgesia disappeared after 30 minutes but could be maintained for 100 min following the injection of a mixture of bestatin and the enkephalinase inhibitor, N-carboxymethyl-L-phenylalanyl-L-leucine. This work suggests that in the slug, a physical stressor produces an analgesia which may be due to the release of endogenous opiates. PMID:2568626

Dalton, L M; Widdowson, P S

1989-01-01

161

Characterization of Activity of a Potential Food-Grade Leucine Aminopeptidase from Kiwifruit  

PubMed Central

Aminopeptidase (AP) activity in ripe but firm fruit of Actinidia deliciosa was characterized using L-leucine-p-nitroanilide as a substrate. The enzyme activity was the highest under alkaline conditions and was thermolabile. EDTA, 1,10-phenanthroline, iodoacetamide, and Zn2+ had inhibitory effect while a low concentration of dithiothreitol (DTT) had stimulatory effect on kiwifruit AP activity. However, DTT was not essential for the enzyme activity. The results obtained indicated that the kiwifruit AP was a thiol-dependent metalloprotease. Its activity was the highest in the seeds, followed by the core and pericarp tissues of the fruit. The elution profile of the AP activity from a DEAE-cellulose column suggested that there were at least two AP isozymes in kiwifruit: one unadsorbed and one adsorbed fractions. It is concluded that useful food-grade aminopeptidases from kiwifruit could be revealed using more specific substrates. PMID:21076540

Premarathne, A. A. A.; Leung, David W. M.

2010-01-01

162

Evaluation of selected micronized poloxamers as tablet lubricants.  

PubMed

The primary objective of this study was to compare the lubrication properties of micronized poloxamer 188 (Lmicrotrol micro 68) and micronized poloxamer 407 (Lmicrotrol micro 127) with certain conventional lubricants such as magnesium stearate and stearic acid. The secondary objective was to use these micronized poloxamers as water-soluble tablet lubricants in preparation of effervecsent tablets. The results showed that these micronized poloxamers have superior lubrication properties compared with stearic acid, with no negative effect on tablet hardness, friability, disintegration, or dissolution. Moreover, lubricant mixing time had no significant effect on tablet properties when poloxamers were used as lubricants. Effervescent tablets also were produced successfully using micronized poloxamers as lubricants. The micronized poloxamers had a better lubrication effect in comparison with that of water-soluble lubricant l-leucine. PMID:17994358

Desai, D; Zia, H; Quadir, A

2007-10-01

163

Crystal structure of the dipeptide binding protein from Escherichia coli involved in active transport and chemotaxis.  

PubMed Central

The Escherichia coli periplasmic dipeptide binding protein functions in both peptide transport and taxis toward peptides. The structure of the dipeptide binding protein in complex with Gly-Leu (glycyl-L-leucine) has been determined at 3.2 A resolution. The binding site for dipeptides is designed to recognize the ligand's backbone while providing space to accommodate a variety of side chains. Some repositioning of protein side chains lining the binding site must occur when the dipeptide's second residue is larger than leucine. The protein's fold is very similar to that of the Salmonella typhimurium oligopeptide binding protein, and a comparison of the structures reveals the structural basis for the dipeptide binding protein's preference for shorter peptides. PMID:8563629

Dunten, P.; Mowbray, S. L.

1995-01-01

164

The gas chromatographic resolution of DL-isovaline  

NASA Technical Reports Server (NTRS)

Isovaline is of cosmological interest because it is one of the 12 non-protein amino acids which have been isolated from the Murchison meteorite, and unlike the other chiral amino acids in this meteorite, it has no alpha-hydrogen at its asymmetric center and hence cannot racemize by the customary alpha-hydrogen-dependent mechanisms which engender racemization in ordinary amino acids. Experiments were conducted in which a .01 M solution of N-TFA-DL-isovalyl-L-leucine isopropyl ester in nitromethane was injected into the capillary column of a gas chromatograph coupled to a digital electronic integrator-recorder. Efflux times and integrated peak area percents are shown next to each diastereometer peak.

Flores, J. J.; Bonner, W. A.; Van Dort, M. A.

1977-01-01

165

Modification of Microbial Polymalic Acid With Hydrophobic Amino Acids for Drug-Releasing Nanoparticles  

PubMed Central

Microbial poly(?, l-malic acid) was modified with either l-leucine ethyl ester (L) or l-phenylalanine methyl ester (F) to produce amphiphylic copolymers. The degradation of these copolymers in aqueous buffer took place under physiological conditions in a few weeks by hydrolysis of the side chain ester group followed by cleavage of the main chain. Spherical nanoparticles with diameters ranging between 70 and 230 nm were prepared from these copolymers by the dialysis-precipitation method. No alteration of the cell viability was observed after incubation of these nanoparticles in different cell lines. Anticancer drugs temozolomide and doxorubicin were encapsulated in the nanoparticles. Temozolomide was released within several hours whereas doxorubicin took several weeks to be completely liberated. PMID:24954994

Lanz-Landázuri, Alberto; Portilla-Arias, José; de Ilarduya, Antxon Martínez; Holler, Eggehard; Ljubimova, Julia; Muñoz-Guerra, Sebastián

2014-01-01

166

New proctolin analogs modified in position 3 of peptide chain--synthesis and their biological evaluation.  

PubMed

Six proctolin analogs modified in position 3 of peptide chain such as Arg-Tyr-X-Pro-Thr where X = Gly (1), Val (2), Pro (3), Thr (4), Acp (1-aminocyclopentane-1-carboxylic acid residue) (5), and Ach (1-aminocyclohexane-1-carboxylic acid residue) (6) were synthesized by liquid-phase method. Biological effects of the pentapeptides (1-6) were examined in cardiostimulatory test in vitro in respect to two insect species: American cockroach (Periplaneta americana L.) and yellow mealworm (Tenebrio molitor L.). Results thus obtained pointed out that the presence of L-leucine in the position 3 of proctolin skeleton plays important role in its cardiotropic activity in insects. PMID:1297114

Konopi?ska, D; Rosi?ski, G; Sobótka, W

1992-01-01

167

Purification and Characterization of Leu-Proteinase, the Leucine Specific Serine Proteinase from Spinach (Spinacia oleracea L.) Leaves 1  

PubMed Central

The leucine specific serine proteinase present in the soluble fraction of leaves from Spinacia oleracea L. (called Leu-proteinase) has been purified by acetone precipitation and a combination of gel-filtration, ion exchange, and adsorption chromatography. This enzyme shows a molecular weight of 60,000 ± 3,000 daltons, an isoelectric point of 4.8 ± 0.1, and a relative electrophoretic mobility of 0.58 ± 0.03. The Leu-proteinase catalyzed hydrolysis of p-nitroanilides of N-?-substituted(-l-)amino acids as well as of chromogenic macromolecular substrates has been investigated between pH 5 and 10 at 23 ± 0.5°C and I = 0.1 molar. The enzyme activity is characterized by a bell-shaped profile with an optimum pH value around 7.5, reflecting the acid-base equilibrium of groups with pKa values of 6.8 ± 0.1 and 8.2 ± 0.1 (possibly the histidyl residue present at the active site of the enzyme and the N-terminus group). Among the substrates considered, N-?-benzoyl-l-leucine p-nitroanilide shows the most favorable catalytic parameters and allows to determine an enzyme concentration as low as 1 × 10?9 molar. In agreement with the enzyme specificity, only N-?-tosyl-l-leucine chloromethyl ketone, di-isopropyl fluorophosphate and phenylmethylsulfonyl fluoride, among compounds considered specific for serine enzymes, strongly inhibit the Leu-proteinase. Accordingly, the enzyme activity is insensitive to cations, chelating agents, sulfydryl group reagents, and activators. PMID:16664908

Aducci, Patrizia; Ascenzi, Paolo; Pierini, Marco; Ballio, Alessandro

1986-01-01

168

Dihydromorphine-peptide hybrids with delta receptor agonistic and mu receptor antagonistic actions  

SciTech Connect

The actions of two morphine derivatives with short peptide side chains were evaluated upon the contraction of the isolated mouse vas deferens and upon displacement of /sup 3/H-etorphine from rat brain membranes. NIH-9833 (N-(6,14-endoetheno-7,8-dihydromorphine-7-alpha-carbonyl)-L-phenylalanyl-L-leucine ethyl ester HCl) was a potent agonist upon the vas deferens. Its EC50 for inhibition of the twitch was 1.2 +/- 0.1 nM. Both naltrexone (10/sup -7/ M) a relatively nonselective opioid antagonist, and ICI-174864 (10/sup -/' M) a highly selective delta receptor antagonist, blocked the actions of NIH-9833 which indicates that this drug is a delta receptor agonist. In contrast, NIH-9835 (N-(6,14-endoetheno-7,8-dihydromorphine-7-alpha-carbonyl)-L-glycyl-L-phenylalanyl-L-leucine ethyl ester HCl), which differs from NIH-9835 by the presence of a single amino acid residue, was devoid of opioid agonistic activity but was a potent antagonist of the inhibitory actions on the vas deferens of morphine and sufentanil. NIH-9833 and NIH-9835 were potent displacers of /sup 3/H-etorphine from rat cerebral membranes with EC50's of 0.58 nM and 1.7 nM, respectively. The observation that addition of a single glycyl group changes a dihydromorphine-peptide analog from a potent delta receptor agonist to an equally potent mu receptor antagonist suggests that the two receptor sites might be structurally quite similar.

Smith, C.B.; Medzihradsky, F.; Woods, J.H.

1986-03-05

169

System L amino acid transporter LAT1 accumulates O-(2-fluoroethyl)-L-tyrosine (FET).  

PubMed

O-(2-fluoroethyl)-L-tyrosine (FET) labeled with fluorine-18 is an important and specific tracer for diagnostics of glioblastoma via positron emission tomography (PET). However, the mechanism of its quite specific accumulation in tumor tissue has not been understood so far. In this work we demonstrate that [(3)H]L-tyrosine is primarily transported by the system L transporter LAT1 in human LN229 glioblastoma cells. FET reduced tyrosine transport, suggesting that it shares the same uptake pathway. More importantly, accumulation of FET was significantly reduced after siRNA-mediated downregulation of LAT1. Xenopus laevis oocytes expressing human LAT1 together with the glycoprotein 4F2hc (necessary to pull LAT-1 to the plasma membrane) exhibited a similar accumulation of FET as observed in glioblastoma cells. In contrast, no accumulation was observed in control oocytes, not overexpressing an exogenous transporter. Because LAT1 works exclusively as an exchanger of amino acids, substrates at one side of the membrane stimulate exchange against substrates at the other side. Extracellular FET stimulated the efflux of intracellular [(3)H]L-leucine, demonstrating that FET is indeed an influx substrate for LAT1. However, FET injected into oocytes was not able to stimulate uptake of extracellular [(3)H]L-leucine, indicating that FET is not a good efflux substrate. Our data, therefore, suggest that FET is trapped within cells due to the asymmetry of its intra- and extracellular recognition by LAT1. If also found for other transporters in tumor cells, asymmetric substrate recognition may be further exploited for tumor-specific accumulation of PET-tracers and/or other tumor-related drugs. PMID:25385314

Habermeier, A; Graf, J; Sandhöfer, B F; Boissel, J-P; Roesch, F; Closs, Ellen I

2015-02-01

170

Assessment of the metabolic pathways associated with glucose-stimulated biphasic insulin secretion.  

PubMed

Biphasic glucose-stimulated insulin secretion involves a rapid first phase followed by a prolonged second phase of insulin secretion. The biochemical pathways that control these 2 phases of insulin secretion are poorly defined. In this study, we used a gas chromatography mass spectroscopy-based metabolomics approach to perform a global analysis of cellular metabolism during biphasic insulin secretion. A time course metabolomic analysis of the clonal ?-cell line 832/13 cells showed that glycolytic, tricarboxylic acid, pentose phosphate pathway, and several amino acids were strongly correlated to biphasic insulin secretion. Interestingly, first-phase insulin secretion was negatively associated with L-valine, trans-4-hydroxy-L-proline, trans-3-hydroxy-L-proline, DL-3-aminoisobutyric acid, L-glutamine, sarcosine, L-lysine, and thymine and positively with L-glutamic acid, flavin adenine dinucleotide, caprylic acid, uridine 5'-monophosphate, phosphoglycerate, myristic acid, capric acid, oleic acid, linoleic acid, and palmitoleic acid. Tricarboxylic acid cycle intermediates pyruvate, ?-ketoglutarate, and succinate were positively associated with second-phase insulin secretion. Other metabolites such as myo-inositol, cholesterol, DL-3-aminobutyric acid, and L-norleucine were negatively associated metabolites with the second-phase of insulin secretion. These studies provide a detailed analysis of key metabolites that are either negatively or positively associated with biphasic insulin secretion. The insights provided by these data set create a framework for planning future studies in the assessment of the metabolic regulation of biphasic insulin secretion. PMID:24564396

Huang, Mei; Joseph, Jamie W

2014-05-01

171

Enhancement of ascomycin production in Streptomyces hygroscopicus var. ascomyceticus by combining resin HP20 addition and metabolic profiling analysis.  

PubMed

Combinatorial approach of adsorbent resin HP20 addition and metabolic profiling analysis were carried out to enhance ascomycin production. Under the optimal condition of 5 % m/v HP20 added at 24 h, ascomycin production was increased to 380 from 300 mg/L. To further rationally guide the improvement of ascomycin production, metabolic profiling analysis was employed to investigate the intracellular metabolite changes of Streptomyces hygroscopicus var. ascomyceticus FS35 in response to HP20 addition. A correlation between the metabolic profiles and ascomycin accumulation was revealed by partial least-squares to latent structures discriminant analysis, and 11 key metabolites that most contributed to metabolism differences and ascomycin biosynthesis were identified. Based on the analysis of metabolite changes together with their pathways, the potential key factors associated with ascomycin overproduction were determined. Finally, rationally designed fermentation strategies based on HP20 addition were performed as follows: 2 % v/v n-hexadecane was added at 24 h; 1.0 g/L valine was supplemented at 48 h; 1.0 g/L lysine was added at 72 h. The ascomycin production was ultimately improved to 460 mg/L, a 53.3 % enhancement compared with that obtained in initial condition. These results demonstrated that the combination of HP20 addition and metabolic profiling analysis could be successfully applied to the rational guidance of production improvement of ascomycin, as well as other clinically important compounds. PMID:24965502

Qi, Haishan; Zhao, Sumin; Fu, Hong; Wen, Jianping; Jia, Xiaoqiang

2014-09-01

172

ilvB-encoded acetolactate synthase is resistant to the herbicide sulfometuron methyl.  

PubMed Central

The herbicide sulfometuron methyl is a potent inhibitor of the branched-chain amino acid biosynthetic enzyme acetolactate synthase (ALS) isolated from bacteria, fungi, and plants. However, it did not prevent growth of wild-type Salmonella typhimurium LT2 or Escherichia coli K-12. These species each contain two acetolactate synthase isozymes. Growth of S. typhimurium and E. coli mutants lacking ALS I was prevented by the herbicide, suggesting that activity of the remaining ALS isoenzyme (II or III, respectively) was stopped by sulfometuron methyl. Synthesis of ALS I requires either an relA function or an elevated cyclic AMP level. A relA mutant of S. typhimurium was inhibited by sulfometuron methyl on rich carbon sources that display a basal cyclic AMP level but not on poor carbon sources where the cyclic AMP concentration is elevated. When L-valine, which allosterically inhibits ALS I activity, was added, growth retardation of the relA- strain by sulfometuron methyl was observed on both poor and rich carbon sources. Enzymological analyses indicated that ALS I activities derived from both species were resistant to the herbicide. In contrast, activities of S. typhimurium ALS II and E. coli ALS III were abolished by sulfometuron methyl. PMID:6090425

LaRossa, R A; Smulski, D R

1984-01-01

173

Spectroscopic studies on the influence of 10 mol% of glycine on nonlinear optical crystal L-valinium picrate  

NASA Astrophysics Data System (ADS)

Nonlinear optics is a fascinating field, which plays a vital role in the emerging field of photonics and optoelectronics. A new nonlinear optical crystal of glycine mixed L-valine picrate (GVP) have been grown from saturated aqueous solution by slow evaporation method at a temperature of 36 °C using a constant temperature bath of accuracy of ±0.01 °C. The synthesized organic optical material has been purified by repeated recrystallization. Single crystal X-ray diffraction analysis has been made to determine the cell parameters and it confirms the crystal lattice to be orthorhombic. UV-vis-NIR spectrum have recorded for GVP crystals in the range from 190 nm to 1100 nm and it is found that the crystal has cut-off at 450 nm. Fourier transform infrared transmission has confirmed the presence of the functional group present in the title compound. The spectrum has been recorded by KBr pellet technique. The 1H and 13C NMR spectra have been recorded to elucidate the molecular structure of GVP crystals. The second harmonic generation (SHG) of the grown crystal have been confirmed by Kurtz-Perry method using Nd:YAG laser as source.

Antony Joseph, A.; John David Ebenezar, I.; Ramachandra Raja, C.

2011-11-01

174

Crystallization of l-alanine in the presence of additives on a circular PMMA platform designed for metal-assisted and microwave-accelerated evaporative crystallization†  

PubMed Central

Crystallization of l-alanine in the presence of l-valine and l-tryptophan additives on a circular poly(methyl) methacrylate (PMMA) platform designed for Metal-Assisted and Microwave-Accelerated Evaporative Crystallization (MA-MAEC) technique was investigated. Theoretical simulations predicted homogeneous temperature and electric field distributions across the circular PMMA platforms during microwave heating. Crystallization of l-alanine with and without additives on the blank and silver nanoparticle films (SNFs) modified sides of the circular PMMA platform occurred within 32–50 min using MA-MAEC technique, while the identical solutions crystallized within 161–194 min at room temperature. Optical microscopy studies revealed that l-alanine crystals without additives were found to be smaller in size and had several well-developed faces, whereas l-alanine crystals grown with additives appeared to be larger and had only one dominant highly-developed face. Raman spectroscopy and powder X-ray diffraction (XRD) measurements showed that all l-alanine crystals had identical peaks, despite the morphological differences between the l-alanine crystals with and without additives observed by optical microscope images. PMID:23378822

Alabanza, Anginelle M.; Mohammed, Muzaffer

2013-01-01

175

Crystallization of l-alanine in the presence of additives on a circular PMMA platform designed for metal-assisted and microwave-accelerated evaporative crystallization.  

PubMed

Crystallization of l-alanine in the presence of l-valine and l-tryptophan additives on a circular poly(methyl) methacrylate (PMMA) platform designed for Metal-Assisted and Microwave-Accelerated Evaporative Crystallization (MA-MAEC) technique was investigated. Theoretical simulations predicted homogeneous temperature and electric field distributions across the circular PMMA platforms during microwave heating. Crystallization of l-alanine with and without additives on the blank and silver nanoparticle films (SNFs) modified sides of the circular PMMA platform occurred within 32-50 min using MA-MAEC technique, while the identical solutions crystallized within 161-194 min at room temperature. Optical microscopy studies revealed that l-alanine crystals without additives were found to be smaller in size and had several well-developed faces, whereas l-alanine crystals grown with additives appeared to be larger and had only one dominant highly-developed face. Raman spectroscopy and powder X-ray diffraction (XRD) measurements showed that all l-alanine crystals had identical peaks, despite the morphological differences between the l-alanine crystals with and without additives observed by optical microscope images. PMID:23378822

Alabanza, Anginelle M; Mohammed, Muzaffer; Aslan, Kadir

2012-12-21

176

AUTORADIOGRAPHIC STUDY OF SUGAR AND AMINO ACID ABSORPTION BY EVERTED SACS OF HAMSTER INTESTINE  

PubMed Central

Autoradiographs were prepared from frozen sections of everted sacs of hamster jejunum which had been incubated in vitro with C14- or H3-labeled sugars and amino acids. When such tissue was incubated in 1 mM solutions of L-valine or L-methionine, columnar absorptive cells at tips of villi accumulated these amino acids to concentrations ranging from 5 to 50 millimoles per liter of cells. Quantitative data were obtained by microdensitometry of C14 autoradiographs. Similar, though less striking, results were obtained with the sugars: galactose, 3-0-methylglucose, ?-methylglucoside, and 6-deoxyglucose. In all cases the marked "step-up" in concentration occurred near the brush border of the cell, and a "step-down" in concentration occurred at the basal pole of the cell. Known inhibitors of intestinal absorption, e.g., phlorizin in the case of sugars, blocked the concentrative step at the luminal border of the absorptive cell. It is inferred from these data that active transport systems for sugars and amino acids reside in the brush border region of the cell. Additional evidence suggests that the basal membrane of the cell may be the site of both a diffusion barrier and a weak transport system directed into the cell. PMID:19866662

Kinter, William B.; Wilson, T. Hastings

1965-01-01

177

Resolution and isolation of enantiomers of (±)-isoxsuprine using thin silica gel layers impregnated with l-glutamic acid, comparison of separation of its diastereomers prepared with chiral derivatizing reagents having l-amino acids as chiral auxiliaries.  

PubMed

Thin silica gel layers impregnated with optically pure l-glutamic acid were used for direct resolution of enantiomers of (±)-isoxsuprine in their native form. Three chiral derivatizing reagents, based on DFDNB moiety, were synthesized having l-alanine, l-valine and S-benzyl-l-cysteine as chiral auxiliaries. These were used to prepare diastereomers under microwave irradiation and conventional heating. The diastereomers were separated by reversed-phase high-performance liquid chromatography on a C18 column with detection at 340 nm using gradient elution with mobile phase containing aqueous trifluoroacetic acid and acetonitrile in different compositions and by thin-layer chromatography (TLC) on reversed phase (RP) C18 plates. Diastereomers prepared with enantiomerically pure (+)-isoxsuprine were used as standards for the determination of the elution order of diastereomers of (±)-isoxsuprine. The elution order in the experimental study of RP-TLC and RP-HPLC supported the developed optimized structures of diastereomers based on density functional theory. The limit of detection was 0.1-0.09 µg/mL in TLC while it was in the range of 22-23 pg/mL in HPLC and 11-13 ng/mL in RP-TLC for each enantiomer. The conditions of derivatization and chromatographic separation were optimized. The method was validated for accuracy, precision, limit of detection and limit of quantification. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25044026

Bhushan, Ravi; Nagar, Hariom

2015-03-01

178

Synthesis, structural elucidation, biological, antioxidant and nuclease activities of some 5-Fluorouracil-amino acid mixed ligand complexes  

NASA Astrophysics Data System (ADS)

Some biologically active mixed ligand complexes (1-9) have been synthesized from 5-Fluorouracil (5-FU; A) and amino acids (B) such as glycine (gly), L-alanine (ala) and L-valine (val) with Ni(II), Cu(II) and Zn(II) ions. The synthesized mixed ligand complexes (1-9) were characterized by various physico-chemical, spectral, thermal and morphological studies. 5-Fluorouracil and its mixed ligand complexes have been tested for their in vitro biological activities against some pathogenic bacterial and fungal species by the agar well diffusion method. The in vitro antioxidant activities of 5-Fluorouracil and its complexes have also been investigated by using the DPPH assay method. The results demonstrate that Cu(II) mixed ligand complexes (4-6) exhibit potent biological as well as antioxidant activities compared to 5-Fluorouracil and Ni(II) (1-3) and Zn(II) (7-9) mixed ligand complexes. Further, the cleaving activities of CT DNA under aerobic conditions show moderate activity with the synthesized Cu(II) and Ni(II) mixed ligand complexes (1-6) while no activity is seen with Zn(II) complexes (7-9). Binding studies of CT DNA with these complexes show a decrease in intensity of the charge transfer band to the extent of 5-15% along with a minor red shift. The free energy change values (?‡G) calculated from intrinsic binding constants indicate that the interaction between mixed ligand complex and DNA is spontaneous.

Shobana, Sutha; Subramaniam, Perumal; Mitu, Liviu; Dharmaraja, Jeyaprakash; Arvind Narayan, Sundaram

2015-01-01

179

Metabolomics Study of Resina Draconis on Myocardial Ischemia Rats Using Ultraperformance Liquid Chromatography/Quadrupole Time-of-Flight Mass Spectrometry Combined with Pattern Recognition Methods and Metabolic Pathway Analysis  

PubMed Central

Resina draconis (bright red resin isolated from Dracaena cochinchinensis, RD) has been clinically used for treatment of myocardial ischemia (MI) for many years. However, the mechanisms of its pharmacological action on MI are still poorly understood. This study aimed to characterize the plasma metabolic profiles of MI and investigate the mechanisms of RD on MI using ultraperformance liquid chromatography/quadrupole time-of-flight mass spectrometry-based metabolomics combined with pattern recognition methods and metabolic pathway analysis. Twenty metabolite markers characterizing metabolic profile of MI were revealed, which were mainly involved in aminoacyl-tRNA biosynthesis, phenylalanine, tyrosine, and tryptophan biosynthesis, vascular smooth muscle contraction, sphingolipid metabolism, and so forth. After RD treatment, however, levels of seven MI metabolite markers, including phytosphingosine, sphinganine, acetylcarnitine, cGMP, cAMP, L-tyrosine, and L-valine, were turned over, indicating that RD is likely to alleviate MI through regulating the disturbed vascular smooth muscle contraction, sphingolipid metabolism, phenylalanine metabolism, and BCAA metabolism. To our best knowledge, this is the first comprehensive study to investigate the mechanisms of RD for treating MI, from a metabolomics point of view. Our findings are very valuable to gain a better understanding of MI metabolic profiles and provide novel insights for exploring the mechanisms of RD on MI. PMID:23762136

Gu, Haiwei; Song, Yunlong; Dong, Xin; Liu, Aijun; Lou, Ziyang; Fan, Guorong; Chai, Yifeng

2013-01-01

180

Behaviour of ?-aminoadipylcysteine and glutamylcysteine in the presence of intact and disrupted mycelium of a Cephalosporium sp  

PubMed Central

1. ?-(l-?-Aminoadipyl)-l-cysteine, the corresponding d- and dl-?-aminoadipyl isomers, ?-(dl-?-amino[6-14C]adipyl)-l-cysteine and ?- and ?-l-glutamyl-l-cysteine were synthesized. 2. The behaviour of ?-(l-aminoadipyl)-l-cysteine and the corresponding d- and dl-?-aminoadipyl isomers was studied in the presence of suspensions of intact mycelium of a Cephalosporium sp., suspensions treated ultrasonically and extracts obtained by grinding with alumina. 3. With intact mycelium the l-?-aminoadipyl isomer was removed more rapidly from the extracellular fluid than the corresponding d-isomer. 4. Addition of ?-(dl-?-amino[6-14C]adipyl)-l-cysteine to suspensions of intact mycelium led to the labelling of extracellular and intracellular penicillin N and cephalosporin C, but also to extensive hydrolysis of the dipeptide. 5. Broken-cell systems hydrolysed ?-(l-?-aminoadipyl)-l-cysteine and the corresponding d-?-aminoadipyl isomer, but the former was hydrolysed more readily than the latter. 6. ?- and ?-l-Glutamyl-l-cysteine were also hydrolysed but ?-(l-?-aminoadipyl)-l-cysteinyl-l-valine was not. 7. Only part of the enzyme activity in broken-cell systems responsible for the hydrolysis of ?-(?-aminoadipyl)-l-cysteine was present in the supernatant obtained on centrifugation at 20000g. 8. Possible implications of these findings are discussed. PMID:5817719

Loder, P. Bronwen; Abraham, E. P.; Newton, G. G. F.

1969-01-01

181

Recoupling of chemical shift anisotropies in solid-state NMR under high-speed magic-angle spinning and in uniformly 13C-labeled systems  

NASA Astrophysics Data System (ADS)

We demonstrate the possibility of recoupling chemical shift anisotropy (CSA) interactions in solid-state nuclear magnetic resonance (NMR) under high-speed magic-angle spinning (MAS) while retaining a static CSA powder pattern line shape and simultaneously attenuating homonuclear dipole-dipole interactions. CSA recoupling is accomplished by a rotation-synchronized radio-frequency pulse sequence with symmetry properties that permit static CSA line shapes to be obtained. We suggest a specific recoupling sequence, which we call ROCSA, for which the scaling factors for CSA and homonuclear dipole-dipole interactions are 0.272 and approximately 0.05, respectively. This sequence is suitable for high-speed 13C MAS NMR experiments on uniformly 13C-labeled organic compounds, including biopolymers. We demonstrate the ROCSA sequence experimentally by measuring the 13C CSA patterns of the uniformly labeled, polycrystalline compounds L-alanine and N-acetyl-D,L-valine at MAS frequencies of 11 and 20 kHz. We also present experimental data for amyloid fibrils formed by a 15-residue fragment of the ?-amyloid peptide associated with Alzheimer's disease, in which four amino acid residues are uniformly labeled, demonstrating the applicability to biochemical systems of high molecular weight and significant complexity. Analysis of the CSA patterns in the amyloid fibril sample demonstrates the utility of ROCSA measurements as probes of peptide and protein conformation in noncrystalline solids.

Chan, Jerry C. C.; Tycko, Robert

2003-05-01

182

Multiple pathways from three types of sugar receptor sites to metabotropic transduction pathways of the blowfly: study by the whole cell-clamp experiments.  

PubMed

Multiple pathways from three types of multiple receptor sites to three types of metabotropic signal transduction pathways were investigated in the whole cell-clamp experiments using isolated labellar sugar receptor neurons (cells) of the adult blowfly, Phormia regina. First, the concentration-response curves of three types of sweet taste components specialized to multiple receptor sites were obtained: sucrose for the pyranose sites (P-sites), fructose for the furanose sites (F-sites), and l-valine for the alkyl sites (R-sites). Next, the effects of inhibitors such as 2', 5'-dideoxyadenosine on adenylyl cyclase in the cAMP pathway, LY 83583 on guanylyl cyclase in the cGMP pathway, and U-73122 on phospholipase C in the IP? pathway were examined. The results showed that all of the inhibitors affected each specific target in the second-messenger transduction pathways. The obtained results verified that the P-site corresponded to the cAMP, the F-site to the cGMP, and the R-site to the IP? transduction pathway, and that these three signal pathways did not have crossing points. PMID:21624494

Kan, Hideko; Kataoka-Shirasugi, Naoko; Amakawa, Taisaku

2011-09-01

183

Identification and biosynthesis of novel male specific esters in the wings of the tropical butterfly, Bicyclus martius sanaos.  

PubMed

Representatives of the highly speciose tropical butterfly genus Bicyclus (Lepidoptera: Nymphalidae) are characterized by morphological differences in the male androconia, a set of scales and hair pencils located on the surface of the wings. These androconia are assumed to be associated with the release of courtship pheromones. In the present study, we report the identification and biosynthetic pathways of several novel esters from the wings of male B. martius sanaos. We found that the volatile compounds in this male butterfly were similar to female-produced moth sex pheromones. Components associated with the male wing androconial areas were identified as ethyl, isobutyl and 2-phenylethyl hexadecanoates and (11Z)-11-hexadecenoates, among which the latter are novel natural products. By topical application of deuterium-labelled fatty acid and amino acid precursors, we found these pheromone candidates to be produced in patches located on the forewings of the males. Deuterium labels from hexadecanoic acid were incorporated into (11Z)-11-hexadecenoic acid, providing experimental evidence of a ?11-desaturase being active in butterflies. This unusual desaturase was found previously to be involved in the biosynthesis of female-produced sex pheromones of moths. In the male butterflies, both hexadecanoic acid and (11Z)-11-hexadecenoic acid were then enzymatically esterified to form the ethyl, isobutyl and 2-phenylethyl esters, incorporating ethanol, isobutanol, and 2-phenylethanol, derived from the corresponding amino acids L-alanine, L-valine, and L-phenylalanine. PMID:24894159

Wang, Hong-Lei; Brattström, Oskar; Brakefield, Paul M; Francke, Wittko; Löfstedt, Christer

2014-06-01

184

Development and validation of a systematic UPLC-MS/MS method for simultaneous determination of three phenol impurities in ritonavir.  

PubMed

A stability indicating gradient reverse phase UPLC-MS/MS method was developed and validated for the simultaneous determination of three phenol impurities in ritonavir drug substance. The chromatographic separation was performed on Acquity UPLC BEH C18 column (100 mm × 2.1 mm, 1.7 ?m) using gradient elution of 0.05% ammonia in methanol and 5.0 mM ammonium acetate buffer (30:70, v/v) at a flow rate of 0.2 mL/min. Both negative and positive electrospray ionization (ESI) modes were operated simultaneously for the quantification of three phenol impurities. The total run time was 11 min, within which ritonavir and its three impurities were well separated. The developed method was validated as per ICH guidelines with respect to specificity, linearity, limit of detection, limit of quantification, accuracy, precision and robustness. The calibration curves showed a good linearity over the concentration range of 0.3-1.5 ppm for phenol and 0.1-1.5 ppm for both 4-nitrophenol and N-phenoxycarbonyl-L-valine (NPV). The determination coefficient obtained was >0.9998 in each case. The method had very low limit of detection (LOD) and limit of quantification (LOQ) and the accuracy lies between 97.8% and 103.2% for all the three phenol impurities. The developed method was successfully applied for five formulation batches of ritonavir to determine its phenol impurities. PMID:24366213

Venugopal, N; Vijaya Bhaskar Reddy, A; Madhavi, G

2014-03-01

185

A cross-polarization based rotating-frame separated-local-field NMR experiment under ultrafast MAS conditions  

NASA Astrophysics Data System (ADS)

Rotating-frame separated-local-field solid-state NMR experiments measure highly resolved heteronuclear dipolar couplings which, in turn, provide valuable interatomic distances for structural and dynamic studies of molecules in the solid-state. Though many different rotating-frame SLF sequences have been put forth, recent advances in ultrafast MAS technology have considerably simplified pulse sequence requirements due to the suppression of proton-proton dipolar interactions. In this study we revisit a simple two-dimensional 1H-13C dipolar coupling/chemical shift correlation experiment using 13C detected cross-polarization with a variable contact time (CPVC) and systematically study the conditions for its optimal performance at 60 kHz MAS. In addition, we demonstrate the feasibility of a proton-detected version of the CPVC experiment. The theoretical analysis of the CPVC pulse sequence under different Hartmann-Hahn matching conditions confirms that it performs optimally under the ZQ (w1H - w1C = ±wr) condition for polarization transfer. The limits of the cross polarization process are explored and precisely defined as a function of offset and Hartmann-Hahn mismatch via spin dynamics simulation and experiments on a powder sample of uniformly 13C-labeled L-isoleucine. Our results show that the performance of the CPVC sequence and subsequent determination of 1H-13C dipolar couplings are insensitive to 1H/13C frequency offset frequency when high RF fields are used on both RF channels. Conversely, the CPVC sequence is quite sensitive to the Hartmann-Hahn mismatch, particularly for systems with weak heteronuclear dipolar couplings. We demonstrate the use of the CPVC based SLF experiment as a tool to identify different carbon groups, and hope to motivate the exploration of more sophisticated 1H detected avenues for ultrafast MAS.

Zhang, Rongchun; Damron, Joshua; Vosegaard, Thomas; Ramamoorthy, Ayyalusamy

2015-01-01

186

A rapid wound signal activates the systemic synthesis of bioactive jasmonates in Arabidopsis.  

PubMed

Jasmonic acid (JA) and its biologically active derivatives (bioactive JAs) perform a critical role in regulating plant responses to wound stress. The perception of bioactive JAs by the F-box protein COI1 triggers the SCF(COI1)/ubiquitin-dependent degradation of JASMONATE ZIM-DOMAIN (JAZ) proteins that repress the expression of JA-response genes. JA is required for many wound-inducible systemic defense responses, but little is known about the role of the hormone in long-distance signal relay between damaged and undamaged leaves. Here, we show that the wounding of Arabidopsis thaliana leaves results in the rapid (<5 min) accumulation of jasmonoyl-l-isoleucine (JA-Ile), the bioactive form of JA, in leaves distal to the wound site. The rapid systemic increase in JA-Ile preceded the onset of early transcriptional responses, and was associated with JAZ degradation. Wound-induced systemic production of JA-Ile required the JA biosynthetic enzyme 12-oxo-phytodienoic acid (OPDA) reductase 3 (OPR3) in undamaged responding leaves, but not in wounded leaves, and was largely dependent on the JA-conjugating enzyme JAR1. Interestingly, the wound-induced synthesis of JA/JA-Ile in systemic leaves was correlated with a rapid decline in OPDA levels. These results are consistent with a model in which a rapidly transmitted wound signal triggers the systemic synthesis of JA, which, upon conversion to JA-Ile, activates the expression of early response genes by the SCF(COI1)/JAZ pathway. PMID:19473329

Koo, Abraham J K; Gao, Xiaoli; Jones, A Daniel; Howe, Gregg A

2009-09-01

187

Amino acid geochronology of the type Cromerian of West Runton, Norfolk, UK.  

PubMed

Aminostratigraphic studies of continental deposits in the UK have hitherto relied almost exclusively on data from the aragonitic shells of non-marine molluscs for dating Pleistocene sequences. This is usually based on the d/l value of a single amino acid, d-alloisoleucine/l-isoleucine (A/I), in the total shell proteins. Two genera of freshwater gastropods (Valvata and Bithynia) are used to explore the value of using multiple amino acids from the intra-crystalline fraction, which should be more protected from the effects of diagenesis than the inter-crystalline component. Results are compared from both the aragonitic shells and opercula composed of calcite, a more stable form of calcium carbonate. In order to put the amino acid data from the West Runton Freshwater Bed into perspective, statistical analyses are used to compare them with results from the Hoxnian (MIS 11) site at Clacton-on-Sea, Essex. Twelve protein decomposition indicators revealed that the results from the shells were not as clear-cut as those from the opercula. Five indicators from the Valvata shell suggest that West Runton is older than Clacton (at a 95% significance level), but two actually suggested a younger age. Seven indicators show that the Bithynia shells from West Runton are older than congeneric shells from Clacton. In marked contrast, all 12 indicators isolated from the opercula demonstrate that West Runton is significantly older than Clacton. The data are also compared with results from Waverley Wood, an important archaeological site in the English Midlands falling within the 'Cromerian Complex'. Contrary to earlier interpretations, the new amino acid data from Bithynia opercula indicate that West Runton is older than Waverley Wood, a relationship now consistent with the available biostratigraphy. PMID:21217810

Penkman, K E H; Preece, R C; Keen, D H; Collins, M J

2010-12-01

188

Barrier repair therapy for facial atopic eczema with a non-steroidal emollient cream containing rhamnosoft, ceramides and iso-leucine. A six-case report series.  

PubMed

Atopic eczema (AE) is a skin disease very common in paediatric population and face region is commonly involved. AE of the face represents a therapeutic challenge limiting the use, especially for long periods, of corticosteroid topical products due to the high risk of atrophic skin changes. Skin barrier alterations and reduction of innate immune mechanisms (reduced levels of anti-microbial peptides) are now considered the hallmarks of AE. Therefore emollient and barrier repair therapies with topical steroid-free substances could be an alternative or an adjuvant strategy in managing AE especially for the face. A non-steroidal, anti-inflammatory moisturizing cream with barrier repair actions, containing rhamnosoft, ceramides and L-isoleucine (ILE) (Nutratopic pro-AMP) has been recently developed for the specific treatment of AE of the face. We report a series of 6 pediatric cases (2 female and 4 male, age from 6 months to 4 years) with facial eczema in children treated with pro-AMP cream for two/four weeks as single treatment, applied twice daily in the affected area with photograph documentation (baseline and after treatment). Pictures of the skin lesions at baseline and after treatment were taken in all cases using a high-definition digital camera. Pro-AMP cream use was associated with a clinical relevant improvement of all signs of eczema. The product was well tolerated. This case series document the clinical efficacy of a barrier repair therapy cream containing rhamnosoft, ceramides and iso-leucine in the treatment of atopic eczema of the face. PMID:25198568

Puviani, M; Agostinis, F; Milani, M

2014-08-01

189

A cross-polarization based rotating-frame separated-local-field NMR experiment under ultrafast MAS conditions.  

PubMed

Rotating-frame separated-local-field solid-state NMR experiments measure highly resolved heteronuclear dipolar couplings which, in turn, provide valuable interatomic distances for structural and dynamic studies of molecules in the solid-state. Though many different rotating-frame SLF sequences have been put forth, recent advances in ultrafast MAS technology have considerably simplified pulse sequence requirements due to the suppression of proton-proton dipolar interactions. In this study we revisit a simple two-dimensional (1)H-(13)C dipolar coupling/chemical shift correlation experiment using (13)C detected cross-polarization with a variable contact time (CPVC) and systematically study the conditions for its optimal performance at 60kHz MAS. In addition, we demonstrate the feasibility of a proton-detected version of the CPVC experiment. The theoretical analysis of the CPVC pulse sequence under different Hartmann-Hahn matching conditions confirms that it performs optimally under the ZQ (w1H-w1C=±wr) condition for polarization transfer. The limits of the cross polarization process are explored and precisely defined as a function of offset and Hartmann-Hahn mismatch via spin dynamics simulation and experiments on a powder sample of uniformly (13)C-labeled L-isoleucine. Our results show that the performance of the CPVC sequence and subsequent determination of (1)H-(13)C dipolar couplings are insensitive to (1)H/(13)C frequency offset frequency when high RF fields are used on both RF channels. Conversely, the CPVC sequence is quite sensitive to the Hartmann-Hahn mismatch, particularly for systems with weak heteronuclear dipolar couplings. We demonstrate the use of the CPVC based SLF experiment as a tool to identify different carbon groups, and hope to motivate the exploration of more sophisticated (1)H detected avenues for ultrafast MAS. PMID:25486635

Zhang, Rongchun; Damron, Joshua; Vosegaard, Thomas; Ramamoorthy, Ayyalusamy

2015-01-01

190

Direct and individual analysis of stress-related phytohormone dispersion in the vascular system of Cucurbita maxima after flagellin 22 treatment.  

PubMed

• The stress-related phytohormones, salicylic acid (SA) and abscisic acid (ABA), and the three jasmonates, jasmonic acid (JA), cis-12-oxo-phytodienoic acid (cis-OPDA), and (+)-7-iso-jasmonoyl-L-isoleucine (JA-Ile), were investigated in phloem and xylem exudates of Cucurbita maxima. • Phloem and xylem exudates were separately collected and analysed via liquid chromatography-mass spectrometry. • We show direct evidence for all three jasmonates, ABA, and SA in both phloem and xylem exudates of C. maxima. JA and JA-Ile concentrations are higher in xylem (JA: c(xylem) ? 199.5 nM, c(phloem) ? 43.9 nM; JA-Ile: c(xylem) ? 7.9 nM, c(phloem) ? 1.6 nM), whereas ABA and SA concentrations are higher in phloem exudates (ABA: c(xylem) ? 37.1 nM, c(phloem) ? 142.6 nM; SA: c(xylem) ? 61.6 nM, c(phloem) ? 1319 nM). During bacteria-derived flagellin 22 (flg22)-triggered remote root-to-shoot signalling, phytohormone concentration changed rapidly both in phloem and xylem. • The unequal distribution of phytohormones suggests that phloem and xylem have distinct roles in defence responses. Our data shed light on systemic phytohormone signalling and help explain how plants cope with environmental challenges by lateral exchange between phloem and xylem. Our analysis is a starting point for further investigations of how phytohormones contribute to phloem- and xylem-based defence signalling. PMID:24387138

Furch, Alexandra C U; Zimmermann, Matthias R; Kogel, Karl-Heinz; Reichelt, Michael; Mithöfer, Axel

2014-03-01

191

Onset of herbivore-induced resistance in systemic tissue primed for jasmonate-dependent defenses is activated by abscisic acid  

PubMed Central

In Arabidopsis, the MYC2 transcription factor on the one hand and the AP2/ERF transcription factors ORA59 and ERF1 on the other hand regulate distinct branches of the jasmonic acid (JA) signaling pathway in an antagonistic fashion, co-regulated by abscisic acid (ABA) and ethylene, respectively. Feeding by larvae of the specialist herbivorous insect Pieris rapae (small cabbage white butterfly) results in activation of the MYC-branch and concomitant suppression of the ERF-branch in insect-damaged leaves. Here we investigated differential JA signaling activation in undamaged systemic leaves of P. rapae-infested plants. We found that the MYC2 transcription factor gene was induced both in the local insect-damaged leaves and the systemic undamaged leaves of P. rapae-infested Arabidopsis plants. However, in contrast to the insect-damaged leaves, the undamaged tissue did not show activation of the MYC-branch marker gene VSP1. Comparison of the hormone signal signature revealed that the levels of JA and (+)-7-iso-jasmonoyl-L-isoleucine raised to similar extents in locally damaged and systemically undamaged leaves, but the production of ABA and the JA precursor 12-oxo-phytodienoic acid was enhanced only in the local herbivore-damaged leaves, and not in the distal undamaged leaves. Challenge of undamaged leaves of pre-infested plants with either P. rapae larvae or exogenously applied ABA led to potentiated expression levels of MYC2 and VSP1, with the latter reaching extremely high expression levels. Moreover, P. rapae-induced resistance, as measured by reduction of caterpillar growth on pre-infested plants, was blocked in the ABA biosynthesis mutant aba2-1, that was also impaired in P. rapae-induced expression of VSP1. Together, these results suggest that ABA is a crucial regulator of herbivore-induced resistance by activating primed JA-regulated defense responses upon secondary herbivore attack in Arabidopsis. PMID:24416038

Vos, Irene A.; Verhage, Adriaan; Schuurink, Robert C.; Watt, Lewis G.; Pieterse, Corné M. J.; Van Wees, Saskia C. M.

2013-01-01

192

Aminostratigraphy of Middle and Late Pleistocene deposits in The Netherlands and the southern part of the North Sea Basin  

NASA Astrophysics Data System (ADS)

A review of all available amino acid racemization D (alloisoleucine)/L (isoleucine) data from the whole shell of four molluscan species from Late and late Middle Pleistocene deposits of the Netherlands is presented. The data allow the distinction of 5 aminostratigraphical units, NAZ (Netherlands Amino Zone) A-E, each representing a temperate stage. The zones are correlated with marine isotope stages 1, 5e, 7, 9, and 11 respectively. Apart from NAZ-D (MIS 9), in all aminozones the marine transgression reached the present-day onshore area of the Netherlands. The transgression during NAZ-C (Oostermeer Interglacial: MIS 7) seems to be at least as widespread as its counterpart during NAZ-B (Eemian: MIS 5e) in the southern bight of the North Sea Basin. The stratigraphic position of the Oostermeer Interglacial is just below deposits of the Drente phase of the Saalian and because of this position the interglacial marine deposits have formerly erroneously considered to be of Holsteinian age. Neede, the 'classic' Dutch Holsteinian site, is dated in NAZ-E (MIS 11), like Noordbergum. Although the validity of these zones has been checked with independent data, some overlap between succeeding zones may occur. The relation between amino acid data from elsewhere in the North Sea Basin and the Netherlands amino zonation is discussed. The deposits at the Holsteinian stratotype Hummelsbüttel in North West Germany are dated in NAZ-D. This interglacial correlates with MIS 9. The Belvédère Interglacial, which is of importance for its archaeology, is in NAZ-D (MIS 9) and therefore of Holsteinian age as well. The lacustroglacial 'pottery clays' in the Noordbergum area are deposits from two glacial stages, which can be correlated with MIS 8 and 10 (the Elsterian). The pottery clay that is considered equivalent to the German 'Lauenburger Ton' correlates with MIS 10.

Meijer, T.; Cleveringa, P.

2009-09-01

193

Stetson Pit, Dare County, North Carolina: An integrated chronologic, faunal, and floral record of subsurface coastal quaternary sediments  

USGS Publications Warehouse

Continuous split spoon samples from a drill hole penetrating 34 m of coastal plain sediments at Stetson Pit in Dare County, North Carolina were taken for lithologic, aminostratigraphic, faunal (ostracodes) and floral (pollen) analyses. Three distinct aminozones are recognized in the subsurface section based upon D-alloisoleucine/L-isoleucine (A/I) values in each of the molluscan species Mulinia lateralis and Mercenaria sp. Ostracode zonations in the subsurface section are based on percentages of 80 thermophilic and cryophilic species (those living today south and north of Cape Hatteras) and the percentages of brackish water species. Five assemblage zones are delineated. Six pollen assemblage zones are also delineated within the subsurface section based upon study of 48 sediment samples. The subsurface record at Stetson Pit is interpreted to represent portions of four interglacials based upon the combined faunal, floral and aminostratigraphic data. The two younger aminozones, with amino acid age estimates of 100,000??20,000 yr (-7.2 to -11.2 m MSL) and 300,000-500,000 yr (-13 to -14.2 m MSL), represent portions of middle/late Pleistocene interglacials. The lower aminozone (-17.4 to -33 m MSL) spans an interval that probably includes at least two interglacials (based upon faunal and floral records) and has an age estimated to be between 800,000 and 1,300,000 yr. Boundaries delineated by faunal, floral, and amino acid methods do not always coincide, due to sampling constraints and phase lags between the different records. One major unconformity (at -17.4 m MSL) in the Stetson Pit section is easily recognized from lithologic characteristics and may represent a hiatus of as much as 800,000 yr. Lithologic changes associated with all other zone boundaries are subtle and would probably not be considered significant in the absence of faunal, floral, or amino acid data. ?? 1989.

York, L.L.; Wehmiller, J. F.; Cronin, T. M.; Ager, T.A.

1989-01-01

194

Amino acid geochronology of the type Cromerian of West Runton, Norfolk, UK  

PubMed Central

Aminostratigraphic studies of continental deposits in the UK have hitherto relied almost exclusively on data from the aragonitic shells of non-marine molluscs for dating Pleistocene sequences. This is usually based on the d/l value of a single amino acid, d-alloisoleucine/l-isoleucine (A/I), in the total shell proteins. Two genera of freshwater gastropods (Valvata and Bithynia) are used to explore the value of using multiple amino acids from the intra-crystalline fraction, which should be more protected from the effects of diagenesis than the inter-crystalline component. Results are compared from both the aragonitic shells and opercula composed of calcite, a more stable form of calcium carbonate. In order to put the amino acid data from the West Runton Freshwater Bed into perspective, statistical analyses are used to compare them with results from the Hoxnian (MIS 11) site at Clacton-on-Sea, Essex. Twelve protein decomposition indicators revealed that the results from the shells were not as clear-cut as those from the opercula. Five indicators from the Valvata shell suggest that West Runton is older than Clacton (at a 95% significance level), but two actually suggested a younger age. Seven indicators show that the Bithynia shells from West Runton are older than congeneric shells from Clacton. In marked contrast, all 12 indicators isolated from the opercula demonstrate that West Runton is significantly older than Clacton. The data are also compared with results from Waverley Wood, an important archaeological site in the English Midlands falling within the ‘Cromerian Complex’. Contrary to earlier interpretations, the new amino acid data from Bithynia opercula indicate that West Runton is older than Waverley Wood, a relationship now consistent with the available biostratigraphy. PMID:21217810

Penkman, K.E.H.; Preece, R.C.; Keen, D.H.; Collins, M.J.

2010-01-01

195

Catabolism of L-methionine in the formation of sulfur and other volatiles in melon (Cucumis melo L.) fruit.  

PubMed

Sulfur-containing aroma volatiles are important contributors to the distinctive aroma of melon and other fruits. Melon cultivars and accessions differ in the content of sulfur-containing and other volatiles. L-methionine has been postulated to serve as a precursor of these volatiles. Incubation of melon fruit cubes with ¹³C- and ²H-labeled L-methionine revealed two distinct catabolic routes into volatiles. One route apparently involves the action of an L-methionine aminotransferase and preserves the main carbon skeleton of L-methionine. The second route apparently involves the action of an L-methionine-?-lyase activity, releasing methanethiol, a backbone for formation of thiol-derived aroma volatiles. Exogenous L-methionine also generated non-sulfur volatiles by further metabolism of ?-ketobutyrate, a product of L-methionine-?-lyase activity. ?-Ketobutyrate was further metabolized into L-isoleucine and other important melon volatiles, including non-sulfur branched and straight-chain esters. Cell-free extracts derived from ripe melon fruit exhibited L-methionine-?-lyase enzymatic activity. A melon gene (CmMGL) ectopically expressed in Escherichia coli, was shown to encode a protein possessing L-methionine-?-lyase enzymatic activity. Expression of CmMGL was relatively low in early stages of melon fruit development, but increased in the flesh of ripe fruits, depending on the cultivar tested. Moreover, the levels of expression of CmMGL in recombinant inbred lines co-segregated with the levels of sulfur-containing aroma volatiles enriched with +1 m/z unit and postulated to be produced via this route. Our results indicate that L-methionine is a precursor of both sulfur and non-sulfur aroma volatiles in melon fruit. PMID:23402686

Gonda, Itay; Lev, Shery; Bar, Einat; Sikron, Noga; Portnoy, Vitaly; Davidovich-Rikanati, Rachel; Burger, Joseph; Schaffer, Arthur A; Tadmor, Ya'akov; Giovannonni, James J; Huang, Mingyun; Fei, Zhangjun; Katzir, Nurit; Fait, Aaron; Lewinsohn, Efraim

2013-05-01

196

Novel approaches to the synthesis and cooperative assembly of inorganic materials utilizing block copolypeptides  

NASA Astrophysics Data System (ADS)

Biominerals and biocomposites are highly ornate and functional materials. Nature controls the properties of these materials by organizing their organic and inorganic constituents on the atomic, molecular, nano, and micron scales. The remarkable precision and complexity of this organization is accomplished using a combination of electrostatics, hydrogen bonding, disulfide bonding, and other molecular-level interactions. The goal of the work described in this dissertation was to use the principles employed by Nature in the biological assembly of biomaterials as inspiration for developing (1) completely synthetic and novel composite materials, and (2) new general methods for the synthesis of composite materials. Specifically, block copolypeptides were used as structure-directing agents in several successful applications of this approach. One application involves the rational design of an organic polymer molecule to direct the crystallization of calcium carbonate into microspheres. I have shown that the doubly-hydrophilic block copolypeptide poly{Nepsilon-2[2-(2 methoxy-ethoxy)ethoxy]acetyl-L-lysine}100-block-poly(L-aspartate sodium salt)30 can act as the structure-directing agent in this process. In addition, control over the morphology of calcium carbonate crystals can be exerted using anionic, amphiphilic block copolypeptides, such as poly(L-aspartate sodium salt)100-block-poly(L-phenylalanine- random-L-leucine)50 and poly(L-glutamate sodium salt) 100-block-poly(L-phenylalanine-random-L-leucine) 50. I have demonstrated that microspheres of calcium carbonate can be prepared by introducing the polymer additive during crystallization. These self-assembling polymers control the precipitation of the microspheres by acting as templates for sphere formation. Another application involves the organization of magnetic nanoparticles into well-defined, soluble nanoclusters. First, I have demonstrated that highly crystalline, monodisperse maghemite (gamma-Fe2O3) nanoparticles, synthesized in organic solvents, can be transferred effectively into an aqueous medium using an ammonium salt. The nanoparticles remain monodisperse, as characterized by TEM and XRD, as well as superparamagnetic, as determined by SQUID magnetometry. Then when the aqueous maghemite is combined with the biologically-inspired block copolypeptide poly(EG2-L-lys) 100-block-poly(L-asp)30, the nanoparticles assemble into uniform clusters of approximately twenty nanoparticles. These water-soluble, block copolypeptide-nanoparticle structures have been characterized by TEM, SQUID, and XRD. Furthermore, I have shown that it is possible to tag the polypeptides with folate molecules (cell-targeting ligands) to produce magnetic microshells with potential applications in the biological imaging and drug delivery fields.

Euliss, Larken E.

197

Antigenic, microbicidal and antiparasitic properties of an l-amino acid oxidase isolated from Bothrops jararaca snake venom.  

PubMed

Venoms from the bee Apis mellifera, the caterpillar Lonomia achelous, the spiders Lycosa sp. and Phoneutria nigriventer, the scorpions Tityus bahiensis and Tityus serrulatus, and the snakes Bothrops alternatus, Bothrops jararaca, Bothrops jararacussu, Bothrops moojeni, Bothrops neuwiedi, Crotalus durissus terrificus, and Lachesis muta were assayed (800mug/mL) for activity against Staphylococcus aureus. Venoms from B. jararaca and B. jararacussu showed the highest S. aureus growth inhibition and also against other Gram-positive and Gram-negative bacteria. To characterize the microbicidal component(s) produced by B. jararaca, venom was fractionated through gel exclusion chromatography. The high molecular weight, anti-S. aureus P1 fraction was further resolved by anion exchange chromatography through Mono Q columns using a 0-0.5M NaCl gradient. Bactericidal Mono Q fractions P5 and P6 showed significant LAAO activity using l-leucine as substrate. These fractions were pooled and subjected to Heparin affinity chromatography, which rendered a single LAAO activity peak. The anti-S. aureus activity was abolished by catalase, suggesting that the effect is dependent on H(2)O(2) production. SDS-PAGE of isolated LAAO indicated the presence of three isoforms since deglycosylation with a recombinant N-glycanase rendered a single 38.2 kDa component. B. jararaca LAAO specific activity was 142.7 U/mg, based on the oxidation of l-leucine. The correlation between in vivo neutralization of lethal toxicity (ED(50)) and levels of horse therapeutic antibodies anti-LAAO measured by ELISA was investigated to predict the potency of Brazilian antibothropic antivenoms. Six horses were hyperimmunized with Bothrops venoms (50% from B. jararaca and 12.5% each from B. alternatus, B. jararacussu, B. neuwiedii and B. moojeni). To set up an indirect ELISA, B. jararaca LAAO and crude venom were used as antigens. Correlation coefficients (r) between ED(50) and ELISA antibody titers against B. jararaca venom and LAAO were 0.846 (p<0.001) and 0.747 (p<0.001), respectively. The hemolytic and leishmanicidal (anti-Leishmania amazonensis) activity of LAAO was also determined. PMID:19101583

Ciscotto, P; Machado de Avila, R A; Coelho, E A F; Oliveira, J; Diniz, C G; Farías, L M; de Carvalho, M A R; Maria, W S; Sanchez, E F; Borges, A; Chávez-Olórtegui, C

2009-03-01

198

Valine needs of male broilers from 42 to 56 days of age.  

PubMed

An experiment was conducted using Ross x Ross 308 males to estimate the proportion of dietary valine needed to optimize performance in broilers from 42 to 56 d of age. All birds received common feeds from 0 to 42 d, and then experimental diets were given to 56 d of age. A diet consisting of corn, soybean meal, and corn gluten meal (17% CP, 3.25 kcal of ME/g) having 0.60% valine served as basal feed. All other essential amino acids were above recommended levels. Successive additions of 0.07% of L-valine were isonitrogenously substituted for L-glutamic acid up to a total of 0.81%. Regression analysis (95% of response) indicated that valine at 0.72% of the diet maximized body weight gain, whereas 0.73% optimized feed conversion. Depot fat removed from the abdominal cavity after processing was unaltered, and weights of resultant chilled carcasses maximized at 0.73% valine in parallel with final live weight. The amount of fillets recovered from chilled carcasses optimized at 0.73% valine; however, the incidence of distinctive blood streaks in the meat (splash) progressively increased with valine as did the level of redness apart from streaking, based on light reflectance. Given lysine at 0.85%, a ratio of 0.86 with valine appears to be adequate. The presently determined requirement of 0.73% total valine (0.67% digestible) for broiler males from 42 to 56 d of age is slightly higher than the 0.70% recommended by the NRC. PMID:15206621

Corzo, A; Moran, E T; Hoehler, D

2004-06-01

199

Impact of different CO2/HCO3- levels on metabolism and regulation in Corynebacterium glutamicum.  

PubMed

We investigated the growth kinetics and transcriptional responses of Corynebacterium glutamicum in environments with low (pCO2<40 mbar) and high (pCO2 ? 300 mbar) CO2/HCO3(-) levels compared to standard conditions. When cultivated at high CO2/HCO3(-)-levels, C. glutamicum showed increased (63%) biomass to substrate yields during the initial growth phase. Other kinetic parameters such as growth rate (?), specific glucose consumption rate (qS), and selected enzymatic activities of anaplerotic reactions, the pentose phosphate pathway and the tricarboxylic acid cycle were similar to standard conditions. However, microarray hybridization disclosed a complex transcriptional response involving 117 differentially expressed genes. Among those, 60 genes were assigned to the complete DtxR/RipA regulon controlling iron homeostasis in C. glutamicum. Impaired growth of a ?dtxR mutant at high CO2/HCO3(-) levels validated the relevance of this master regulator to cope with excessive CO2/HCO3(-) availability. At low CO2/HCO3(-) levels, C. glutamicum grew in a bi-level manner with three distinct growth phases. Differential analyses revealed approximately doubled activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase accompanied by the formation of L-alanine and L-valine during the lowest ? occurring in mid-phase of the cultivation. DNA microarray analysis revealed more than 100 differentially expressed genes in growth phase II compared to phase I including almost all thiamin pyrophosphate (TPP) biosynthesis genes, which were significantly up regulated. Concluding, we hypothesize that C. glutamicum counteracts the lack of CO2/HCO3(-) by triggering TPP biosynthesis for increasing the activities of TPP-dependent enzymes involved in CO2 formation. PMID:24140290

Blombach, Bastian; Buchholz, Jens; Busche, Tobias; Kalinowski, Jörn; Takors, Ralf

2013-12-01

200

Synthesis, Chemical and Enzymatic Hydrolysis, and Aqueous Solubility of Amino Acid Ester Prodrugs of 3-Carboranyl Thymidine Analogues for Boron Neutron Capture Therapy of Brain Tumors  

PubMed Central

Various water-soluble L-valine-, L-glutamate-, and glycine ester prodrugs of two 3-Carboranyl Thymidine Analogues (3-CTAs), designated N5 and N5-2OH, were synthesized for Boron Neutron Capture Therapy (BNCT) of brain tumors since the water solubilities of the parental compounds proved to be insufficient in preclinical studies. The amino acid ester prodrugs were prepared and stored as hydrochloride salts. The water solubilities of these amino acid ester prodrugs, evaluated in phosphate buffered saline (PBS) at pH 5, pH 6 and pH 7.4, improved 48 to 6600 times compared with parental N5 and N5-2OH. The stability of the amino acid ester prodrugs was evaluated in PBS at pH 7.4, Bovine serum, and Bovine cerebrospinal fluid (CSF). The rate of the hydrolysis in all three incubation media depended primarily on the amino acid promoiety and, to a lesser extend, on the site of esterification at the deoxyribose portion of the 3-CTAs. In general, 3'-amino acid ester prodrugs were less sensitive to chemical and enzymatic hydrolysis than 5'-amino acid ester prodrugs and the stabilities of the latter decreased in the following order: 5'-valine > 5'-glutamate > 5'-glycine. The rate of the hydrolysis of the 5'-amino acid ester prodrugs in Bovine CSF was overall higher than in PBS and somewhat lower than in Bovine serum. Overall, 5'-glutamate ester prodrug of N5 and the 5'-glycine ester prodrugs of N5 and N5-2OH appeared to be the most promising candidates for preclinical BNCT studies. PMID:22889558

Hasabelnaby, Sherifa; Goudah, Ayman; Agarwal, Hitesh K.; Abd alla, Mosaad S. M.; Tjarks, Werner

2012-01-01

201

Integrative analysis of transcriptomic and metabolomic profiling of ascites syndrome in broiler chickens induced by low temperature.  

PubMed

Ascites syndrome (AS) still has an unacceptably high incidence rate in both humans and animals although there have been many studies on AS. To continue our previous pathological and biochemical investigation on the underlying mechanisms of AS incidence in broiler chickens, cutting-edge technologies including RNA-seq and metabolimics were used by directly comparing AS chickens and healthy controls. The RNA-seq analysis in the liver identified 390 differentially expressed genes (DEGs), among which 212 genes were up-regulated and 178 genes were down-regulated in the AS group compared to the control. For the down-regulated DEGs, further gene ontology (GO) analysis suggested that lipid metabolism, cell differentiation, enzyme linked receptor protein signaling pathway and steroid biosynthesis pathway were significantly enriched. For up-regulated DEGs, the cholesterol metabolic process has the lowest p value (0.000966) of fold enrichment while the cholesterol biosynthetic process has the highest fold enrichment (46.67). The metabolomic analysis of serum revealed statistically significant changes in the concentrations of LysoPC(20?:?4), LysoPC(16?:?0), LysoPC(18?:?0), LysoPC(18?:?1), LysoPC(18?:?2), PC(14?:?1/20?:?1), PC(20?:?4/18?:?0), PC(14?:?1/22?:?1), dihydroxyacetone, indoleacrylic acid, ursodeoxycholic acid, l-valine, and l-tryptophan. The integrative analysis of transcriptome and metabolome indicated that two biological pathways of tryptophan biosynthesis and metabolism, and glycerophospholipid metabolism may contribute to the induction of AS in broilers. These findings have provided novel insights into our understanding of molecular mechanisms of AS incidence in broilers. PMID:25178933

Shi, Shourong; Shen, Yiru; Zhao, Zhenhua; Hou, Zhuocheng; Yang, Ying; Zhou, Huaijun; Zou, Jianmin; Guo, Yuming

2014-11-01

202

Development and validation of enantioselective high performance liquid chromatographic method for Valacyclovir, an antiviral drug in drug substance.  

PubMed

A chiral high performance liquid chromatographic method was developed and validated for the enantiomeric resolution of Valacyclovir, L-valine 2-[(2-amino-1,6-dihydro-6-oxo-9h-purin-9-yl) methoxy] ethyl ester, an antiviral agent in bulk drug substance. The enantiomers of Valacyclovir were resolved on a Chiralpak AD (250 mm x 4.6 mm, 10 microm) column using a mobile phase system containing n-hexane: ethanol: diethylamine (30:70:0.1, v/v/v). The resolution between the enantiomers was found not less than four. The presence of diethylamine in the mobile phase has played an important role in enhancing chromatographic efficiency and resolution between the enantiomers. The developed method was extensively validated and proved to be robust. The limit of detection and limit of quantification of (D)-enantiomer were found to be 300 and 900 ng/ml, respectively, for 20 microL injection volume. The calibration curve showed excellent linearity over the concentration range of 900 ng/ml (LOQ) to 6000 ng/ml for (D)-enantiomer. The percentage recovery of (D)-enantiomer was ranged from 97.50 to 102.18 in bulk drug samples of Valacyclovir. Valacyclovir sample solution and mobile phase were found to be stable for at least 48 h. The proposed method was found to be suitable and accurate for the quantitative determination of (D)-enantiomer in bulk drugs substance. It can be also used to test the stability samples of Valacyclovir. PMID:17196355

Jadhav, A S; Pathare, D B; Shingare, M S

2007-03-12

203

Metabolic engineering Corynebacterium glutamicum for the L-lysine production by increasing the flux into L-lysine biosynthetic pathway.  

PubMed

The experiments presented here were based on the conclusions of our previous results. In order to avoid introduction of expression plasmid and to balance the NADH/NAD ratio, the NADH biosynthetic enzyme, i.e., NAD-dependent glyceraldehyde-3-phosphate dehydrogenase (GADPH), was replaced by NADP-dependent GADPH, which was used to biosynthesize NADPH rather than NADH. The results indicated that the NADH/NAD ratio significantly decreased, and glucose consumption and L-lysine production drastically improved. Moreover, increasing the flux through L-lysine biosynthetic pathway and disruption of ilvN and hom, which involve in the branched amino acid and L-methionine biosynthesis, further improved L-lysine production by Corynebacterium glutamicum. Compared to the original strain C. glutamicum Lys5, the L-lysine production and glucose conversion efficiency (?) were enhanced to 81.0 ± 6.59 mM and 36.45% by the resulting strain C. glutamicum Lys5-8 in shake flask. In addition, the by-products (i.e., L-threonine, L-methionine and L-valine) were significantly decreased as results of genetic modification in homoserine dehydrogenase (HSD) and acetohydroxyacid synthase (AHAS). In fed-batch fermentation, C. glutamicum Lys5-8 began to produce L-lysine at post-exponential growth phase and continuously increased over 36 h to a final titer of 896 ± 33.41 mM. The L-lysine productivity was 2.73 g l(-1) h(-1) and the ? was 47.06% after 48 h. However, the attenuation of MurE was not beneficial to increase the L-lysine production because of decreasing the cell growth. Based on the above-mentioned results, we get the following conclusions: cofactor NADPH, precursor, the flux through L-lysine biosynthetic pathway and DCW are beneficial to improve L-lysine production in C. glutamicum. PMID:24879631

Xu, Jianzhong; Han, Mei; Zhang, Junlan; Guo, Yanfeng; Zhang, Weiguo

2014-09-01

204

L-Serine overproduction with minimization of by-product synthesis by engineered Corynebacterium glutamicum.  

PubMed

The direct fermentative production of L-serine by Corynebacterium glutamicum from sugars is attractive. However, superfluous by-product accumulation and low L-serine productivity limit its industrial production on large scale. This study aimed to investigate metabolic and bioprocess engineering strategies towards eliminating by-products as well as increasing L-serine productivity. Deletion of alaT and avtA encoding the transaminases and introduction of an attenuated mutant of acetohydroxyacid synthase (AHAS) increased both L-serine production level (26.23 g/L) and its productivity (0.27 g/L/h). Compared to the parent strain, the by-products L-alanine and L-valine accumulation in the resulting strain were reduced by 87 % (from 9.80 to 1.23 g/L) and 60 % (from 6.54 to 2.63 g/L), respectively. The modification decreased the metabolic flow towards the branched-chain amino acids (BCAAs) and induced to shift it towards L-serine production. Meanwhile, it was found that corn steep liquor (CSL) could stimulate cell growth and increase sucrose consumption rate as well as L-serine productivity. With addition of 2 g/L CSL, the resulting strain showed a significant improvement in the sucrose consumption rate (72 %) and the L-serine productivity (67 %). In fed-batch fermentation, 42.62 g/L of L-serine accumulation was achieved with a productivity of 0.44 g/L/h and yield of 0.21 g/g sucrose, which was the highest production of L-serine from sugars to date. The results demonstrated that combined metabolic and bioprocess engineering strategies could minimize by-product accumulation and improve L-serine productivity. PMID:25434811

Zhu, Qinjian; Zhang, Xiaomei; Luo, Yuchang; Guo, Wen; Xu, Guoqiang; Shi, Jinsong; Xu, Zhenghong

2014-12-01

205

Application of protein N-terminal amidase in enzymatic synthesis of dipeptides containing acidic amino acids specifically at the N-terminus.  

PubMed

Dipeptides exhibit unique physiological functions and physical properties, e.g., l-aspartyl-l-phenylalanine-methyl ester (Asp-Phe-OMe, aspartame) as an artificial sweetener, and functional studies of peptides have been carried out in various fields. Therefore, to establish a manufacturing process for the useful dipeptides, we investigated its enzymatic synthesis by utilizing an l-amino acid ligase (Lal), which catalyzes dipeptide synthesis in an ATP-dependent manner. Many Lals were obtained, but the Lals recognizing acidic amino acids as N-terminal substrates have not been identified. To increase the variety of dipeptides that are enzymatically synthesized, we proposed a two-step synthesis: Asn-Xaa and Gln-Xaa (Asn, l-asparagine; Gln, l-glutamine; and Xaa, arbitrary amino acids) synthesized by Lals were continuously deamidated by a novel amidase, yielding Asp-Xaa and Glu-Xaa (Asp, l-aspartic acid; and Glu, l-glutamic acid). We searched for amidases that specifically deamidate the N-terminus of Asn or Gln in dipeptides since none have been previously reported. We focused on the protein N-terminal amidase from Saccharomyces cerevisiae (NTA1), and assayed its activity toward dipeptides. Our findings showed that NTA1 deamidated l-asparaginyl-l-valine (Asn-Val) and l-glutaminyl-glycine (Gln-Gly), but did not deamidate l-valyl-l-asparagine and l-alanyl-l-glutamine, suggesting that this deamidation activity is N-terminus specific. The specific activity toward Asn-Val and Gln-Gly were 190 ± 30 nmol min(-1) mg(-1)·protein and 136 ± 6 nmol min(-1) mg(-1)·protein. Additionally, we examined some characteristics of NTA1. Acidic dipeptide synthesis was examined by a combination of Lals and NTA1, resulting in the synthesis of 12 kinds of Asp-Xaa, including Asp-Phe, a precursor of aspartame, and 11 kinds of Glu-Xaa. PMID:23218487

Arai, Toshinobu; Noguchi, Atsushi; Takano, Eriko; Kino, Kuniki

2013-04-01

206

ALTERATIONS IN PROTEIN AND NUCLEIC ACID METABOLISM OF LYMPHOMA 6C3HED-OG CELLS IN MICE GIVEN GUINEA PIG SERUM  

PubMed Central

Lymphoma 6C3HED-OG cells, known from previous work to be susceptible to the effects of guinea pig serum in vivo and dependent upon extrinsic asparagine for protein synthesis and growth in vitro, remained for the most part morphologically intact and countable in the electronic cell counter following exposures of 1 and 2 hr to the effects of heated (56°C, 30 min) guinea pig serum injected into the peritoneal cavities of mice in which the lymphoma cells were growing rapidly; after exposures of 4 and 6 hr the bulk of the -OG cells remained still intact and countable in the cell counter, though by this time a small proportion of them (5 to 12%) proved stainable with eosin in wet preparations) hence were presumably nonviable. After 12, 16, and 24 hr of exposure, however, the bulk of the -OG cells were either lysed or fragmented, to the extent that they did not register in the cell counter. Morphologic studies of the cells exposed 16 and 24 hr to the effects of heated guinea pig serum in vivo, disclosed that most of the cells then remaining were either frankly necrotic or greatly altered otherwise, marked vacuolation of the cytoplasm being the most conspicuous alteration in cells not yet obviously necrotic. Long before the bulk of the Lymphoma 6C3HED-OG cells had become conspicuously changed morphologically following exposure to the effects of heated guinea pig serum in vivo, they manifested striking alterations in protein metabolism, as was disclosed by "pulse" studies with radioactive valine. For example, the protein metabolism of -OG cells, as measured by their incorporation of L-valine-C14, was sharply curtailed following 15 min of exposure to heated guinea pig serum in vivo, as compared with valine incorporation by cells labeled immediately after exposure to the guinea pig serum. Following exposure to heated guinea pig serum during 60 min, -OG cells incorporated less than half as much L-valine-C14 as did cells labeled immediately after exposure, and the incorporation of L-valine-C14 was still less after 120 min of exposure. By contrast, Lymphoma -RG1 cells, known from previous work to be wholly insusceptible to the effects of guinea pig serum in vivo and independent of need for extrinsic asparagine for protein synthesis and growth in vitro, showed no curtailment whatever of protein synthesis following exposures to the effects of heated guinea pig serum in vivo during periods of 15, 60, and 120 min. Reasons are given for considering the prompt inhibition of protein synthesis in the asparagine-dependent -OG cells a direct result of asparagine-deprivation induced in vivo by the injected guinea pig serum, the L-asparaginase of which presumably converted the available L-asparagine of the host to L-aspartic acid that was not taken up by the -OG cells. The synthesis of deoxyribonucleic acid by Lymphoma 6C3HED-OG cells, as measured by the incorporation of thymidme-H3, determined with the aid of liquid scintillation counting and autoradiography, was also altered by exposure of the lymphoma cells to the effects of heated guinea pig serum in vivo, though not during exposures of 15 and 60 min; only after an exposure of 120 min did the population of -OG cells incorporate notably less thymidine-H3 than did control populations, though after 240 min of exposure the -OG cells incorporated less than one-fifth as much tritiated thymidineas had -OG cells exposed to heated guinea pig serum for 60 min or to heated horse serum for periods up to 240 min. Autoradiographs indicated that DNA synthesis by -OG cells normally proceeds at an intense level that leads to some 60% of these cells being heavily labeled in autoradiographs at any given time; after exposure to the effects of heated guinea pig serum during 2 and 4 hr in vivo, however, the lymphoma cells lost their ability to incorporate enough tritiated thymidine to become heavily labeled, but approximately the same proportion of them (56 to 58%) retained their ability to incorporate sufficient tritiated thymidine to become lightly labeled. The possibility is considered that the inhibition

Sobin, Leslie H.; Kidd, John G.

1966-01-01

207

Herbicide Resistance in Datura innoxia 1  

PubMed Central

Acetolactate synthase (ALS, EC 4. 1.3. 18), the first enzyme in the biosynthesis of branched-chain amino acids, was isolated from wild-type and sulfonylurea-resistant Datura innoxia cell variants and characterized. Apparent Km values of the ALS for pyruvate from three sulfonylurea-resistant variants (CSR2, CSR6, and CSR10) were manyfold greater than that of the wild type. The inhibition of wild-type and herbicide-resistant ALS activity by chlorsulfuron (CS), a sulfonylurea herbicide, and l-leucine (l-Leu), one of the feedback inhibitors of the enzyme, was examined. ALS from two CS-resistant variants exhibited severalfold greater resistance to CS than did the wild-type enzyme. Inhibition of ALS by l-Leu fitted a partially competitive pattern most closely. It is proposed that the herbicide resistance mutation accentuated the partial inhibition characteristics of ALS by l-Leu. ALS from one of the two CS-resistant variants (CSR6) had a Ki for l-Leu an order of magnitude greater than that of the wild-type enzyme. The alterations in kinetic properties observed in the ALS from sulfonylurea-resistant variants are discussed in relation to the possible evolutionary significance of the herbicide binding site of this enzyme, the physiological effects of such biochemical alterations, and their practical utility in genetic studies. PMID:16668161

Rathinasabapathi, Bala; King, John

1991-01-01

208

Cell surface glycoproteins of CHO cells. I. Internalization and rapid recycling  

SciTech Connect

The major cell surface proteins of Chinese hamster ovary (CHO) cells have been investigated after reacting cells at 4/sup 0/C with the membrane-impermeant reagent, trinitrobenzenesulfonate (TNBS). Immunoprecipitation and subsequent two-dimensional, sodiumdodecyl sulfate, polyacrylamide gel electrophoresis (SDS-PAGE) of proteins from derivatized cells that had been labelled previously with (/sup 3/H)D-glucosamine or (/sup 3/H)L-leucine showed that TNBS reacted with most of the high molecular weight (HMW) acidic glycoproteins that became labelled with iodine by the lactoperoxidase technique and that bind the lectin, wheat germ agglutinin (WGA). After warming the cells to allow endocytosis to proceed, molecule haptenized with trinitrophenol (TNP) groups were followed radio-chemically by means of (/sup 125/I)anti-DNP antibodies. Within 15 min at 37/sup 0/C, a steady-state between surface and cytoplasmic label was reached, with about 65% of the hapten located internally. Recycling of internalized TNP groups back to the cell surface also occurred rapidly (t/sub 1/2/ approx. 5 min). Our results are consistent with the view that the majority of plasma membrane glycoproteins are continuously being internalized and recycled at a high rate.

Raub, T.J.; Denny, J.B.; Roberts, R.M.

1986-01-01

209

Biochemical and molecular characterization of Saccharomyces cerevisiae strains obtained from sugar-cane juice fermentations and their impact in cachaça production.  

PubMed

Saccharomyces cerevisiae strains from different regions of Minas Gerais, Brazil, were isolated and characterized aiming at the selection of starter yeasts to be used in the production of cachaça, the Brazilian sugar cane spirit. The methodology established took into account the screening for biochemical traits desirable in a yeast cachaça producer, such as no H2S production, high tolerance to ethanol and high temperatures, high fermentative capacity, and the abilities to flocculate and to produce mycocins. Furthermore, the yeasts were exposed to drugs such as 5,5',5"-trifluor-D,L-leucine and cerulenin to isolate those that potentially overproduce higher alcohols and esters. The utilization of a random amplified polymorphic DNA-PCR method with primers based on intron splicing sites flanking regions of the COX1 gene, as well as microsatellite analysis, was not sufficient to achieve good differentiation among selected strains. In contrast, karyotype analysis allowed a clear distinction among all strains. Two selected strains were experimentally evaluated as cachaça producers. The results suggest that the selection of strains as fermentation starters requires the combined use of biochemical and molecular criteria to ensure the isolation and identification of strains with potential characteristics to produce cachaça with a higher quality standard. PMID:18065624

Oliveira, Valdinéia Aparecida; Vicente, Maristela Araújo; Fietto, Luciano Gomes; Castro, Ieso de Miranda; Coutrim, Maurício Xavier; Schüller, Dorit; Alves, Henrique; Casal, Margarida; Santos, Juliana de Oliveira; Araújo, Leandro Dias; da Silva, Paulo Henrique Alves; Brandão, Rogelio Lopes

2008-02-01

210

Universal and species-specific bacterial 'fungiphiles' in the mycospheres of different basidiomycetous fungi.  

PubMed

In previous work, several bacterial groups that show a response to fruiting bodies (the mycosphere) of the ectomycorrhizal fungus Laccaria proxima were identified. We here extend this work to a broader range of fungal fruiting bodies sampled at two occasions. PCR-DGGE analyses showed clear effects of the mycosphere of diverse fungi on the total bacterial and Pseudomonas communities in comparison with those in the corresponding bulk soil. The diversities of the Pseudomonas communities increased dramatically in most of the mycospheres tested, which contrasted with a decrease of the diversity of the total bacterial communities in these habitats. The data also indicated the existence of universal (i.e. Pseudomonas poae, P. lini, P. umsongensis, P. corrugata, P. antarctica and Rahnella aquatilis) as well as specific (i.e. P. viridiflava and candidatus Xiphinematobacter americani) fungiphiles, defined as bacteria adapted to the mycospheres of, respectively, three or more or just one fungal species. The selection of such fungiphiles was shown to be strongly related to their capacities to use particular carbonaceous compounds, as evidenced using principal components analyses of BIOLOG-based substrate utilization tests. The differentiating compounds, i.e. L-arabinose, L-leucine, m-inositol, m-arabitol, D-mannitol and D-trehalose, were tentatively linked to compounds known to occur in mycosphere exudates. PMID:19196267

Warmink, J A; Nazir, R; van Elsas, J D

2009-02-01

211

Inhibitors on an elastase-like enzyme activity catalyzing Suc-Ala-Ala-Pro-Leu-pNA amidolysis in human seminal plasma.  

PubMed

The behavior of some proteinase inhibitors toward the Suc-Ala-Ala-Pro-Leu-pNA amidolytic enzyme activity in human seminal plasma (HSP) was tested. [(2S, 3R)-3-Amino-2-hydroxy-5-methyl-hexanoyl]L-valyl-L-valyl-L-aspartic acid (Amastatin) and 3-[1-[(2-(hydroxymethyl)- -pyrolidinyl)-2-methylpropyl]-carbamoyl] octanohydroxamic acid (Actinonin) showed strong inhibitory effects. No inhibition of this present enzyme activity was seen with anti-human serum (whole), anti-human leukocyte elastase, phenyl-methyl sulfonyl fluoride, Elastatinal, ethyeneglycol bis(beta-aminoethyl ethyl)N,N,N:N'-tetra acetic acid, and [L-3-trans-ethoxycarbonyl-oxirane-2-carbonyl]1-L-leucine(3-methylbutyl)a mido (E-64). No relation was observed between human pancreatic elastase antigen and the Suc-Ala-Ala-Pro-Leu-pNA amidolytic enzyme enzyme activity in HSP. Two peaks of Suc-Ala-Ala-Leu-Pro-pNA amidolytic enzyme activity were separated by Cellulofine GCL-2000 gel filtration and these activities were completely abolished by addition of Amastatin. Suc-Ala-Ala-Pro-Leu-pNA amidolytic enzyme activity in HSP is not an elastase-like metalloproteinase but is rather an acyl amidase-like leucine aminopeptidase. PMID:10690759

Matsuda, Y; Katayama, M; Hara, I; Sato, H; Tomomasa, H; Iizumi, T; Umeda, T; Ishikawa, H

2000-01-01

212

Synthesis of new poly(ether-urethane-urea)s based on amino acid cyclopeptide and PEG: study of their environmental degradation.  

PubMed

Conventional polyurethanes (PUs) are among biomaterials not intended to degrade but are susceptible to hydrolytic, oxidative and enzymatic degradation in vivo. Biodegradable PUs are typically prepared from polyester polyols, aliphatic diisocyanates and chain extenders. In this work we have developed a degradable monomer based on ?-amino acid to accelerate hard segment degradation. Thus a new class of degradable poly(ether-urethane-urea)s (PEUUs) was synthesized via direct reaction of 4,4'-methylene-bis(4-phenylisocyanate) (MDI), L-leucine anhydride (LA) and polyethylene glycol with molecular weight of 1,000 (PEG-1000) as polyether soft segment. The resulting polymers are environmentally biodegradable and thermally stable. Decomposition temperatures for 5 % weight loss occurred above 300 °C by TGA in nitrogen atmospheres. Some structural characterization and physical properties of these polymers before and after degradation in soil, river water and sludge are reported. The environmental degradation of the polymer films was investigated by SEM, FTIR, TGA, DSC, GPC and XRD techniques. A significant rate of degradation occurred in PEUU samples under river water and sludge condition. The polymeric films were not toxic to E. coli (Gram negative), Staphylococcus aureus and Micrococcus (Gram positive) bacteria and showed good biofilm formation on polymer surface. Our results show that hard segment degraded selectively as much as soft segment and these polymers are susceptible to degradation in soil and water. Thus our study shows that new environment-friendly polyurethane, which can degrade in soil, river water and sludge, is synthesized. PMID:22833157

Rafiemanzelat, Fatemeh; Fathollahi Zonouz, Abolfazl; Emtiazi, Giti

2013-02-01

213

Effect of amino acids on the composition and properties of extruded mixtures of wheat flour and glucose.  

PubMed

Wheat flour was extruded at 100-120 degrees C with 5% D-glucose or mixtures of 5% D-glucose and 0.5% or 2.0% of L-alanine, L-leucine, L-lysine, L-threonine or L-cysteine. The extent of browning was only moderate, and yellow and red pigments were produced. The odour intensity increased with the addition of either glucose or a mixture of glucose and amino acids; the odour was not significantly intensive according to sensory acceptancy analysis. The odour profile was influenced by the structure of amino acid present in the extruded material. The addition of D-glucose increased the production of furan derivatives, and in lesser degree, of pyrazines in the extruded product. The pyrazine content increased with the addition of amino acids, except cysteine which enhanced the production of sulphur compounds instead of pyrazines. The composition of the pyrazine fraction varied depending on the amino acid added. Pretreatment of D-glucose with an amino acid in aqueous solution affected the composition of volatiles, but it did not significantly enhance the pyrazine production. PMID:10907241

Farouk, A; Pudil, F; Janda, V; Pokorný, J

2000-06-01

214

Peptide coupling between amino acids and the carboxylic acid of a functionalized chlorido-gold(I)-phosphane.  

PubMed

We have developed a protocol for the direct coupling between methyl ester protected amino acids and the chlorido-gold(I)-phosphane (p-HOOC(C6H4)PPh2)AuCl. By applying the EDC·HCl/NHS strategy (EDC·HCl = N-ethyl-N'-(3-(dimethylamino)propyl)carbodiimide hydrochloride, NHS = N-hydroxysuccinimide), the methyl esters of l-phenylalanine, glycine, l-leucine, l-alanine, and l-methionine are coupled with the carboxylic acid of the gold complex in moderate to good yields (62-88%). All amino acid tagged gold complexes were characterized by (1)H and (13)C NMR spectroscopy and high-resolution mass spectrometry. As corroborated by measurement of the angle of optical rotation, no racemization occurred during the reaction. The molecular structure of the leucine derivative was determined by single-crystal X-ray diffraction. In the course of developing an efficient coupling protocol, the acyl chlorides (p-Cl(O)C(C6H4)PPh2)AuX (X = Cl, Br) were also prepared and characterized. PMID:25203269

Kriechbaum, Margit; List, Manuela; Himmelsbach, Markus; Redhammer, Günther J; Monkowius, Uwe

2014-10-01

215

Inhibition of Sporulation and Ultrastructural Alterations of Grapevine Downy Mildew by the Endophytic Fungus Alternaria alternata.  

PubMed

ABSTRACT One hundred twenty-six endophytic microorganisms isolated from grapevine leaves showing anomalous symptoms of downy mildew were tested on grapevine leaf disks as biocontrol agents against Plasmopara viticola. Among the 126 microorganisms, only five fungal isolates completely inhibited the sporulation of P. viticola; all of them were identified as Alternaria alternata. Ultrastructural analyses were carried out by transmission electron microscopy to observe cellular interactions between P. viticola and A. alternata in the grapevine leaf tissue. Cytological observations indicated that, even without close contact with A. alternata, the P. viticola mycelium showed severe ultrastructural alterations, such as the presence of enlarged vacuoles or vacuoles containing electron-dense precipitates. Haustoria appeared necrotic and irregularly shaped or were enclosed in callose-like substances. Therefore, a toxic action of A. alternata against P. viticola was hypothesized. To examine the production of toxic low-molecular-weight metabolites by A. alternata, we analyzed the fungal liquid culture by thin layer chromatography and proton magnetic resonance spectroscopy. The main low-molecular-weight metabolites produced by the endophyte were three diketopiperazines: cyclo(l-phenylalanine-trans-4-hydroxy-l-proline), cyclo(l-leucine-trans-4-hydroxy-l-proline), and cyclo(l-alanine-trans-4-hydroxy-l-proline). When applied at different concentrations to both grapevine leaf disks and greenhouse plants, a mixture of the three diketopiperazines was very efficacious in limiting P. viticola sporulation. PMID:18943142

Musetti, R; Vecchione, A; Stringher, L; Borselli, S; Zulini, L; Marzani, C; D'Ambrosio, M; di Toppi, L Sanità; Pertot, I

2006-07-01

216

Microplasma discharge ionization source for ambient mass spectrometry.  

PubMed

In this paper, we demonstrate the first use of a microplasma ionization source for ambient mass spectrometry. This device is a robust, easy-to-operate microhollow discharge that enables ambient direct analysis of gaseous, liquid, and solid-phase samples with minimum requirements in terms of operating power and high purity gas consumption. The initial performance of the microplasma device has been evaluated by ionizing samples containing dimethyl sulfoxide (DMSO), dimethylformamide (DMF), methyl salicylate, caffeine, l-leucine, l-histidine, loratadine, ibuprofen, acetaminophen, acetylsalicylic acid, and cocaine in various forms. These molecules are diverse in nature, but almost all have relatively high proton affinities. Thus, the major species observed in all obtained mass spectra corresponded to protonated molecules. Though these microplasmas are known to produce significant densities of metastable species and electrons with mean energies greater than several electronvolt, minimal fragmentation was observed. Background spectra showed prominent signals corresponding to H(+)(H(2)O)(2) ions and a distinct lack of H(3)O(+). Small water cluster ions are likely the dominant proton transfer agents, giving rise to mass spectral data very similar to that obtained using other plasma-based ambient ionization techniques. The simplicity, low cost, low power, low rate of gas consumption, and possibility of being batch-fabricated, makes these microplasma devices attractive candidates as ion sources for miniaturized mass spectrometry and other field detection applications. PMID:20020764

Symonds, Joshua M; Galhena, Asiri S; Fernández, Facundo M; Orlando, Thomas M

2010-01-15

217

Structure of the Mycobacterium tuberculosis proteasome and mechanism of inhibition by a peptidyl boronate  

SciTech Connect

Mycobacterium tuberculosis (Mtb) has the remarkable ability to resist killing by human macrophages. The 750 kDa proteasome, not available in most eubacteria except Actinomycetes, appears to contribute to Mtb's resistance. The crystal structure of the Mtb proteasome at 3.0 Angstroms resolution reveals a substrate-binding pocket with composite features of the distinct {beta}1, {beta}2 and {beta}5 substrate binding sites of eukaryotic proteasomes, accounting for the broad specificity of the Mtb proteasome towards oligopeptides described in the companion article [Lin et al. (2006), Mol Microbiol doi:10.1111/j.1365-2958.2005.05035.x]. The substrate entrance at the end of the cylindrical proteasome appears open in the crystal structure due to partial disorder of the a-subunit N-terminal residues. However, cryo-electron microscopy of the core particle reveals a closed end, compatible with the density observed in negative-staining electron microscopy that depended on the presence of the N-terminal octapeptides of the a-subunits in the companion article, suggesting that the Mtb proteasome has a gated structure. We determine for the first time the proteasomal inhibition mechanism of the dipeptidyl boronate N-(4-morpholine)carbonyl-{beta}-(1-naphthyl)-l-alanine-l-leucine boronic acid (MLN-273), an analogue of the antimyeloma drug bortezomib. The structure improves prospects for designing Mtb-specific proteasomal inhibitors as a novel approach to chemotherapy of tuberculosis.

Hu,G.; Lin, G.; Wang, M.; Dick, L.; Xu, R.; Nathan, C.; Li, H.

2006-01-01

218

The involvement of L-type amino acid transporters in theanine transport.  

PubMed

L-Theanine has favorable physiological effects in terms of human health, but the mechanisms that transport it to its target organs or cells are not completely defined. To identify the major transport mechanisms of L-theanine, we screened for candidate transporters of L-3H-theanine in several mammal cell lines that intrinsically express multiple transporters with various specificities. All of the cells tested, T24, HepG2, COS1, 293A, Neuro2a, and HuH7, absorbed L-3H-theanine. Uptake was significantly inhibited by the addition of L-leucine and by a specific inhibitor of the system L transport system, 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH). L-3H-Theanine uptake occurred mostly independently of Na+. These results indicate that L-theanine was taken up via a system L like transport system in all of the cells tested. Additionally, in experiments using cells stably expressing two system L isoforms, LAT1 and LAT2, we found that the two isoforms mediated L-theanine transport to similar extents. Taken together, our results indicate that L-theanine is transported mostly via the system L transport pathway and its isoforms. PMID:23221699

Yamamoto, Sachiko; Kimura, Toru; Tachiki, Takashi; Anzai, Naohiko; Sakurai, Takuya; Ushimaru, Makoto

2012-01-01

219

Leucyl-tRNA Synthetase Regulates Lactation and Cell Proliferation via mTOR Signaling in Dairy Cow Mammary Epithelial Cells  

PubMed Central

The role of LeuRS, an aminoacyl-tRNA synthetase, as an intracellular l-leucine sensor for the mTORC1 pathway has been the subject of much research recently. Despite this, the association between LeuRS and lactation in dairy cow mammary epithelial cells (DCMECs) remains unknown. In this study, we found that LeuRS expression in mammary gland tissue was significantly higher during lactation than pregnancy. Moreover, our data demonstrates that LeuRS is localized in the cytoplasm. Treatment with leucine increased DCMECs viability and proliferation, as well as mammalian target of rapamycin (mTOR), p-mTOR, ribosomal protein S6 kinase 1 (S6K1), p-S6K1, ?-Casein, sterol regulatory element binding protein 1c (SREBP-1c), glucose transporter 1 (GLUT1), and Cyclin D1 mRNA and protein expression. Secretion of lactose and triglyceride were also increased. siRNA-mediated knockdown of LeuRS led to reduction in all of these processes. Based on these data, LeuRS up-regulates the mTOR pathway to promote proliferation and lactation of DCMECs in response to changes in the intracellular leucine concentration. PMID:24722568

Wang, Lina; Lin, Ye; Bian, Yanjie; Liu, Lili; Shao, Li; Lin, Lin; Qu, Bo; Zhao, Feng; Gao, Xuejun; Li, Qingzhang

2014-01-01

220

Biochemical characterization of the soluble alkaline phosphatase isolated from the venomous snake W. aegyptia.  

PubMed

A soluble form of alkaline phosphatase (ALP) has been identified and purified from Walterinnesia aegyptia venom using an HPLC system Gold 126/1667 equipped with Protein PAK 125 and Protein PAK 60 columns. The enzyme was purified 3.4 fold over crude venom with a yield of 37.3%. On SDS-PAGE under non-reduced conditions the purified enzyme showed three bands of 212 kD, 80 kD, and 55 kD. However, under reducing conditions, the enzyme showed two bands of 80 kD and 55 kD. The specific activity of ALP was 24 U/mg with p-nitrophenylephosphate as the substrate. During isoelectric focusing experiments the ALP exhibited two bands focused at pH 6.2 and 6.8, which suggests that either the enzyme exists as two different isoforms or the two bands in IEF may be two subunits of 80 kD and 55 kD. The kinetic parameters (Km and Vmax) and IC50 of ALP inhibition by L-phenylalanine, L-leucine, imidazole, caffeine, orthophosphate and permanganate were also investigated in the present study. Zinc and cyanide ions at a concentration of 15 mM and 10 mM, respectively, completely inhibited the activity of W. aegyptia ALP. PMID:12503880

Al-Saleh, Saad S M

2002-12-01

221

A molecular dynamics simulation study of the association of 1,1";-binaphthyl-2,2";-diyl hydrogenphosphate enantiomers with a chiral molecular micelle  

NASA Astrophysics Data System (ADS)

Molecular dynamics (MD) simulations were used to investigate the binding of 1,1";-binaphthyl-2,2";-diyl hydrogenphosphate (BNP) enantiomers to the molecular micelle poly-(sodium undecyl-(L,L)-leucine-valine) (poly(SULV)). Poly(SULV) is used as a chiral selector in capillary electrophoresis separations. Four poly(SULV) binding pockets were identified and either (R)-BNP or (S)-BNP were docked into each pocket. MD simulations were then used to identify the preferred BNP binding site. Within the preferred site, both enantiomers formed hydrogen bonds with poly(SULV) and penetrated into the poly(SULV) core. Comparisons of BNP enantiomer binding to the preferred poly(SULV) pocket showed that (S)-BNP formed stronger hydrogen bonds, moved deeper into the binding site, and had a lower poly(SULV) binding free energy than the (R) enantiomer. Finally, MD simulation results were in agreement with capillary electrophoresis and NMR experiments. Each technique showed (S)-BNP interacted more strongly with poly(SULV) than (R)-BNP and that the site of chiral recognition was near the poly(SULV) leucine chiral center.

Morris, Kevin F.; Billiot, Eugene J.; Billiot, Fereshteh H.; Gladis, Ashley A.; Lipkowitz, Kenny B.; Southerland, William M.; Fang, Yayin

2014-08-01

222

Effect of amino acid residues at the cleavable site of substrates on the remarkable activation of thermolysin by salts.  

PubMed Central

The activity of thermolysin in the hydrolysis of N-[3-(2-furyl)acryloyl]-glycyl-L-leucine amide and N-carbobenzoxy-L-aspartyl-L-phenylalanine methyl ester is remarkably enhanced in the presence of high concentrations (1-5 M) of neutral salts [Inouye (1992) J. Biochem. (Tokyo) 112, 335-340]. In this study, the effect of salts on such activity has been examined using a series of substrates, furylacryloyl dipeptide amides, which have various hydrophobic amino acids at the cleavable bond. Although the enzyme activity varies widely depending on the substrate employed, the degree of activation at a given concentration of NaCl is considerably similar. This indicates that the degree of activation is not dependent on the hydrophobicity of the amino acid side chains at the scissile bond of the substrates. The molecular activity, kcat, and Michaelis constant, Km, were evaluated separately for substrates N[3-(2-furyl)acryloyl]-L-leucyl-L-alanine amide and N-[3-(2-furyl)acryloyl]L-phenyl-alanyl-L-alanine amide, and the activation was found to be brought about only by an increase in k(cat'). The effectiveness of monovalent cations on the increase of k(cat) was determined to follow the order of Na(+)>K(+)>Li(+). PMID:8670097

Inouye, K; Lee, S B; Tonomura, B

1996-01-01

223

Myocardial Reloading after Extracorporeal Membrane Oxygenation Alters Substrate Metabolism While Promoting Protein Synthesis  

SciTech Connect

Extracorporeal membrane oxygenation (ECMO) unloads the heart providing a bridge to recovery in children after myocardial stunning. Mortality after ECMO remains high.Cardiac substrate and amino acid requirements upon weaning are unknown and may impact recovery. We assessed the hypothesis that ventricular reloading modulates both substrate entry into the citric acid cycle (CAC) and myocardial protein synthesis. Fourteen immature piglets (7.8-15.6 kg) were separated into 2 groups based on ventricular loading status: 8 hour-ECMO (UNLOAD) and post-wean from ECMO (RELOAD). We infused [2-13C]-pyruvate as an oxidative substrate and [13C6]-L-leucine, as a tracer of amino acid oxidation and protein synthesis into the coronary artery. RELOAD showed marked elevations in myocardial oxygen consumption above baseline and UNLOAD. Pyruvate uptake was markedly increased though RELOAD decreased pyruvate contribution to oxidative CAC metabolism.RELOAD also increased absolute concentrations of all CAC intermediates, while maintaining or increasing 13C-molar percent enrichment. RELOAD also significantly increased cardiac fractional protein synthesis rates by >70% over UNLOAD. Conclusions: RELOAD produced high energy metabolic requirement and rebound protein synthesis. Relative pyruvate decarboxylation decreased with RELOAD while promoting anaplerotic pyruvate carboxylation and amino acid incorporation into protein rather than to the CAC for oxidation. These perturbations may serve as therapeutic targets to improve contractile function after ECMO.

Kajimoto, Masaki; Priddy, Colleen M.; Ledee, Dolena; Xu, Chun; Isern, Nancy G.; Olson, Aaron; Des Rosiers, Christine; Portman, Michael A.

2013-08-19

224

Direct spectrophotometric measurement of angiotensin I-converting enzyme inhibitory activity for screening bioactive peptides.  

PubMed

A direct, extraction-free spectrophotometric assay was developed for determination of angiotensin I-converting enzyme activity (ACE) in the presence of ACE inhibitors using hippuryl-l-histidyl-l-leucine (HHL) as the ACE-specific substrate. This method relies on previously published spectrophotometric determination of hippuric acid (HA) content in the urine, the method of which was based on the specific colorimetric reaction of HA with benzene sulfonyl chloride (BSC) in the presence of quinoline. The proposed ACE inhibition assay was applied to the measurement of the ACE inhibitory activity of Captopril. IC(50) value of Captopril corresponded well with literature data. Furthermore, Alcalase hydrolysates of mung bean and rice protein isolates were assessed for ACE inhibitory activity by this method. These two hydrolysates showed high ACE inhibitory activity. This method proposed here was shown to be direct, sensitive, accurate, reproducible, and less expensive without separation of HA from ACE reaction mixture, and can be used for the screening of ACE inhibitory peptides derived from food proteins. PMID:15708660

Li, Guan-Hong; Liu, Huan; Shi, Yong-Hui; Le, Guo-Wei

2005-02-23

225

Nutritional and regulatory roles of leucine in muscle growth and fat reduction.  

PubMed

The metabolic roles for L-leucine, an essential branched-chain amino acid (BCAA), go far beyond serving exclusively as a building block for de novo protein synthesis. Growing evidence shows that leucine regulates protein and lipid metabolism in animals. Specifically, leucine activates the mammalian target of rapamycin (mTOR) signaling pathway, including the 70 kDa ribosomal protein S6 kinase 1 (S6K1) and eukaryotic initiation factor (eIF) 4E-binding protein 1 (4EBP1) to stimulate protein synthesis in skeletal muscle and adipose tissue and to promote mitochondrial biogenesis, resulting in enhanced cellular respiration and energy partitioning. Activation of cellular energy metabolism favors fatty acid oxidation to CO2 and water in adipocytes, lean tissue gain in young animals, and alleviation of muscle protein loss in aging adults, lactating mammals, and food-deprived subjects. As a functional amino acid, leucine holds great promise to enhance the growth, efficiency of food utilization, and health of animals and humans.  PMID:25553480

Duan, Yehui; Li, Fengna; Liu, Hongnan; Li, Yinghui; Liu, Yingying; Kong, Xiangfeng; Zhang, Yuzhe; Deng, Dun; Tang, Yulong; Feng, Zemeng; Wu, Guoyao; Yin, Yulong

2015-01-01

226

Evidence that synaptosomal high-affinity carriers for amino acid neurotransmitters are glycosylated  

SciTech Connect

The effect of removal of surface sialic acid from synaptosomes on the high-affinity, Na/sup +/-dependent uptake systems for amino acid neurotransmitters was evaluated. Synaptosomes from rat forebrain were preincubated with neuraminidase from Vibrio cholerae for 20 min at 34/sup 0/. After washing and resuspension, their ability to transport /sup 14/C-GABA and the acidic amino acid, /sup 3/H-aspartate was studied. Pretreatment with neuraminidase resulted in a concentration-dependent inhibition of the uptake of both amino acids while the influx of /sup 3/H-L-leucine was unaffected. Inhibition was a function of the amount of sialic acid released from membranes. The analysis of the kinetic parameters of amino acid uptake revealed that inhibition resulted from a decrease of Vmax without any change in the Km. Neither the synaptosomal energy levels nor the internal concentration of potassium ions was affected by the pretreatment with neuraminidase. The maximum accumulation ratios for both amino acids remained largely unaltered. It is concluded that the GABA and acidic amino acid transporters are glycosylated and that sialic acid is involved in the operation of carrier proteins directly and not through modification of the driving forces responsible for amino acid transport.

Zaleska, M.M.; Erecinska, M.

1987-05-01

227

Gastric Mammalian Target of Rapamycin Signaling Regulates Ghrelin Production and Food Intake  

PubMed Central

Ghrelin, a gastric hormone, provides a hunger signal to the central nervous system to stimulate food intake. Mammalian target of rapamycin (mTOR) is an intracellular fuel sensor critical for cellular energy homeostasis. Here we showed the reciprocal relationship of gastric mTOR signaling and ghrelin during changes in energy status. mTOR activity was down-regulated, whereas gastric preproghrelin and circulating ghrelin were increased by fasting. In db/db mice, gastric mTOR signaling was enhanced, whereas gastric preproghrelin and circulating ghrelin were decreased. Inhibition of the gastric mTOR signaling by rapamycin stimulated the expression of gastric preproghrelin and ghrelin mRNA and increased plasma ghrelin in both wild-type and db/db mice. Activation of the gastric mTOR signaling by l-leucine decreased the expression of gastric preproghrelin and the level of plasma ghrelin. Overexpression of mTOR attenuated ghrelin promoter activity, whereas inhibition of mTOR activity by overexpression of TSC1 or TSC2 increased its activity. Ghrelin receptor antagonist d-Lys-3-GH-releasing peptide-6 abolished the rapamycin-induced increment in food intake despite that plasma ghrelin remained elevated. mTOR is therefore a gastric fuel sensor whose activity is linked to the regulation of energy intake through ghrelin. PMID:19406939

Xu, Geyang; Li, Yin; An, Wenjiao; Li, Shenduo; Guan, Youfei; Wang, Nanping; Tang, Chaoshu; Wang, Xian; Zhu, Yi; Li, Xiaoying; Mulholland, Michael W.; Zhang, Weizhen

2009-01-01

228

Protein phosphatase type 1 regulates ion homeostasis in Saccharomyces cerevisiae.  

PubMed Central

Protein phosphatase type 1 (PP1) is encoded by the essential gene GLC7 in Saccharomyces cerevisiae. glc7-109 (K259A, R260A) has a dominant, hyperglycogen defect and a recessive, ion and drug sensitivity. Surprisingly, the hyperglycogen phenotype is partially retained in null mutants of GAC1, GIP2, and PIG1, which encode potential glycogen-targeting subunits of Glc7. The R260A substitution in GLC7 is responsible for the dominant and recessive traits of glc7-109. Another mutation at this residue, glc7-R260P, confers only salt sensitivity, indicating that the glycogen and salt traits of glc7-109 are due to defects in distinct physiological pathways. The glc7-109 mutant is sensitive to cations, aminoglycosides, and alkaline pH and exhibits increased rates of l-leucine and 3,3'-dihexyloxacarbocyanine iodide uptake, but it is resistant to molar concentrations of sorbitol or KCl, indicating that it has normal osmoregulation. KCl suppresses the ion and drug sensitivities of the glc7-109 mutant. The CsCl sensitivity of this mutant is suppressed by recessive mutations in PMA1, which encodes the essential plasma membrane H(+)ATPase. Together, these results indicate that Glc7 regulates ion homeostasis by controlling ion transport and/or plasma membrane potential, a new role for Glc7 in budding yeast. PMID:11973298

Williams-Hart, Tara; Wu, Xiaolin; Tatchell, Kelly

2002-01-01

229

Impact of Core-Forming Segment Structure on Drug Loading in Biodegradable Polymeric Micelles Using PEG-b-Poly(lactide-co-depsipeptide) Block Copolymers  

PubMed Central

We synthesized series of amphiphilic AB-type block copolymers having systematic variation in the core-forming segments using poly(lactide-co-depsipeptide)s as a hydrophobic segment and prepared polymeric micelles using the block copolymers, PEG-b-poly(lactide-co-depsipeptide). We then discussed the relationship between the core-forming segment structure and drug loading efficiency for the polymeric micelles. PEG-b-poly(lactide-co-depsipeptide)s, PEG-b-PLGL containing l-leucine (Leu), and PEG-b-PLGF containing l-phenylalanine (Phe), with similar molecular weights and various mole fractions of depsipeptide units, were synthesized. Polymeric micelles entrapping model drug (fluorescein, FL) were prepared using these copolymers. As a result, PEG-b-poly(lactide-co-depsipeptide) micelles showed higher drug loading compared with PEG-b-PLLA and PEG-b-PDLLA as controls. The drug loading increased with increase in the mole fraction of depsipeptide unit in the hydrophobic segments. The introduction of aliphatic and aromatic depsipeptide units was effective to achieve higher FL loading into the micelles. PEG-b-PLGL micelle showed higher drug loading than PEG-b-PLGF micelle when the amount of FL in feed was high. These results obtained in this study should be useful for strategic design of polymeric micelle-type drug delivery carrier with high drug loading efficiency. PMID:24696855

Takahashi, Akihiro; Ozaki, Yuta; Kuzuya, Akinori

2014-01-01

230

Dynamic proteome analysis of Cyanothece sp. ATCC 51142 under constant light  

SciTech Connect

Understanding the dynamic nature of protein abundances provides insights into protein turnover not readily apparent from conventional, static mass spectrometry measurements. This level of data is particularly informative when surveying protein abundances in biological systems subjected to large perturbations or alterations in environment such as cyanobacteria. Our current analysis expands upon conventional proteomic approaches in cyanobacteria by measuring dynamic changes of the proteome using a 13C15N-L-leucine metabolic labeling in Cyanothece ATCC51142. Metabolically labeled Cyanothece ATCC51142 cells grown under nitrogen sufficient conditions in continuous light were monitored longitudinally for isotope incorporation over a 48 h period, revealing 422 proteins with dynamic changes in abundances. In particular, proteins involved in carbon fixation, pentose phosphate pathway, cellular protection, redox regulation, protein folding, assembly and degradation showed higher levels of isotope incorporation suggesting that these biochemical pathways are important for growth under non-diazotrophic conditions. Calculation of relative isotope abundances (RIA) values allowed to measure actual active protein synthesis over time for different biochemical pathways under non-diazotrophic conditions. Overall results demonstrated the utility of 'non-steady state' pulsed metabolic labeling for systems-wide dynamic quantification of the proteome in Cyanothece ATCC51142 that can also be applied to other cyanobacteria.

Aryal, Uma K.; Stockel, Jana; Welsh, Eric A.; Gritsenko, Marina A.; Nicora, Carrie D.; Koppenaal, David W.; Smith, Richard D.; Pakrasi, Himadri B.; Jacobs, Jon M.

2012-02-03

231

Microbial decomposition in aquatic environments: combined process of extracellular enzyme activity and substrate uptake  

SciTech Connect

The aim of this study was to define a model for the coupling between extracellular enzyme activity and substrate uptake by bacterial populations in natural waters. The balance between uptake of leucine and extracellular hydrolytic production of leucine from a peptide model substrate was investigated in a combined fluorescence-radiotracer experiment with (/sup 3/H) leucine as a marker for the leucine pool and L-leucine-4-methyl-7-coumarinylamide (Leu-MCA) as a marker for the pool of dissolved peptide substrates. Results show that at low concentrations of the model substrate the input and uptake processes of leucine are nearly balanced, whereas at high concentrations of the model substrate much more leucine is liberated than taken up. In addition, samples from one polluted and one less polluted station in the Kiel Fjord were investigated for their extracellular enzymatic and uptake properties in an annual cycle. Calculated on an annual average basis, turnover rates were ca. nine times higher than hydrolysis rates at the polluted station and ca., five times higher at the less polluted station. From the described model, this would mean that the relative fraction of polymers within the total dissolved organic carbon pool (with regard to the substrate combination dissolved protein-leucine) is about twice that at the polluted than at the less polluted station.

Hoppe, H.G.; Kim, S.J.; Gocke, K.

1988-03-01

232

A new antiinflammatory compound, leumedin, inhibits modification of low density lipoprotein and the resulting monocyte transmigration into the subendothelial space of cocultures of human aortic wall cells.  

PubMed Central

Addition of leumedin, N-[9H-(2,7-dimethylfluorenyl-9-methoxy) carbon]-L-leucine at 30-60 microM together with LDL almost completely prevented the induction of monocyte chemotactic protein mRNA, reduced monocyte chemotactic protein 1 levels by 84%, and inhibited monocyte migration into the subendothelial space of cocultures of human aortic wall cells by < or = 98%. LDL incubated with leumedin formed a stable complex that remained intact even after refloating in an ultracentrifuge. Leumedin at 50 microM did not change conjugated diene formation during coculture modification of LDL or Cu++ catalyzed oxidation of LDL. Unlike LDL from control rabbits, LDL isolated from rabbits that were injected with 20 mg/kg leumedin was remarkably resistant to modification by the coculture and did not induce monocyte migration to a significant degree. Moreover, HDL isolated from rabbits injected with leumedin was far more effective in protecting against LDL modification by the artery wall cocultures than HDL from control rabbits. We conclude that leumedins can associate with lipoproteins in vivo, rendering LDL resistant to biological modification and markedly amplifying the protective capacity of HDL against in vitro LDL oxidation by artery wall cells. Images PMID:8450051

Navab, M; Hama, S Y; Van Lenten, B J; Drinkwater, D C; Laks, H; Fogelman, A M

1993-01-01

233

Influence of leucine on arterial concentrations and regional exchange of amino acids in healthy subjects.  

PubMed

1. L-Leucine was given to healthy, post-absorptive subjects as a continuous intravenous infusion (300 mumol/min) during 2 1/2 h. Arterial blood concentrations and regional exchange amino acids were measured across the splanchnic region, the brain and a leg, by the catheter technique. Renal clearance of amino acids was also determined. 2. During the infusion of leucine its concentration rose four- to six-folds, while the concentrations of several other amino acids declined continually, the effect being most pronounced for isoleucine (-55% of initial value), methionine (-55%), valine (-40%), tyrosine (-35%) and phenylalanine (-35%). 3. The infused leucine was taken up by muscle tissue (55%), by the splanchnic region (25%) and by the brain (10%). Neither leg-muscle release nor splanchnic uptake of aromatic amino acids was affected. Renal clearance and tubular reabsorption of amino acids were uninfluenced by leucine infusion. The uptake of isoleucine and methionine by the brain, seen in the basal state, was inhibited during leucine infusion. 4. The marked reduction in the concentrations of the aromatic amino acids, the uptake of leucine by the brain and the inhibition of brain methionine uptake, which accompany leucine infusion in healthy subjects, may be of relevance for the treatment of patients with portal-systemic encephalopathy. PMID:7428288

Hagenfeldt, L; Eriksson, S; Wahren, J

1980-09-01

234

Isolation, purification, and properties of aminopeptidase H from skeletal muscle of the lizard Agama stellio stellio.  

PubMed

Aminopeptidase H was isolated and purified from fresh skeletal muscle of the lizard Agama stellio stellio by ammonium sulfate fractionation and successive chromatographies on DEAE-cellulose, Ultrogel AcA-34, activated thiol-Sepharose 4B, phenyl-Sepharose CL-4B, and DEAE-cellulose again. This is the first report of the isolation of aminopeptidase H from a reptile. The purified enzyme migrated as a single band on SDS-PAGE. The molecular weight of the enzyme was 48 kD by SDS-PAGE and 384 kD on Ultrogel AcA-34 column chromatography. The optimum pH for hydrolysis of L-leucine beta-naphthylamide (Leu-Nap) was 7.8. The Km values for the hydrolysis of Leu-Nap and Nalpha-benzoyl-DL-arginine beta-naphthylamide (BzArg-Nap) were 0.48 and 0.99 mM, respectively. These activities were strongly inhibited by iodoacetic acid and leupeptin but were not affected by EDTA, pepstatin, bestatin, or phenylmethylsulfonyl fluoride. The enzyme has been shown not to hydrolyze proteins such as hemoglobin, BSA, myofibrillar proteins, and sarcoplasmic proteins. PMID:10187916

Al-Jassabi, S

1999-02-01

235

Impact of epiphytic and endogenous enzyme activities of senescent maize leaves and roots on the soil biodegradation process.  

PubMed

This study was focused on investigating the role of the initial residue community, i.e. microorganisms and enzymes from the epiphytic and endophytic compartments, in soil decomposition processes. Aerial and underground parts (leaves and roots) of maize (Zea mays L.) plants were ?-irradiated, surface-sterilized with sodium hypochlorite (NaOCl)/ethanol or non-sterilized (controls), while the outer surface morphology of maize leaves and roots was examined by scanning electron microscopy (SEM). Non-sterilized and sterilized maize leaves and roots were incubated in soil to study carbon (C) mineralization kinetics and enzyme dynamics (L-leucine aminopeptidase, CBH-1, xylanase, cellulase and laccase). SEM results showed that initial microbial colonization was more pronounced on non-sterilized leaf and root surfaces than on sterilized samples. The hypochlorite treatment removed a part of the soluble components of leaves by washing and no specific effect of any type of colonizing microorganisms was observed on C mineralization. In contrast, ? irradiation and hypochlorite treatments did not affect root chemical characteristics and the quantitative effect of initial residue-colonizing microorganisms on C mineralization was demonstrated. The variations in C mineralization and enzyme dynamics between non-sterilized and sterilized roots suggested that activities of epiphytic and endogenic microorganisms were of the same order of magnitude. PMID:22078739

Zafar Amin, Bilal Ahmad; Beaugrand, Johnny; Debeire, Philippe; Chabbert, Brigitte; Bertrand, Isabelle

2011-11-01

236

Specific Counterion Repercussions on the Thermal, pH-Response, and Electrochemical Properties of Side-Chain Leucine Based Chiral Polyelectrolytes.  

PubMed

Effects of counterions of side chain amino acid based polyelectrolytes (PEs) on the solubility in aqueous medium, pH responsiveness, thermal properties, and ionic conductivities have been appraised. Deprotection of the tert-butyl carbamate (Boc) group from poly(Boc-l-leucine methacryloyloxyethyl ester) [P(Boc-l-Leu-HEMA)] was carried out to produce PE with trifluoroacetate as an associative counteranion (1a). PEs with bis(trifluoromethylsulfonyl)imide and hexafluorophosphate counteranion were prepared through anion exchange reactions of 1a. Protonation of the neutralized polymer (2) obtained from 1a, followed by anion exchange, leads to the production of miscellaneous PEs bearing different counteranions, such as tetrafluoroborate, trifluoromethanesulfonate, chloride, and nitrate. Differential scanning calorimetry traces of the PEs reveal that the comparatively larger and weakly coordinated counteranions require less thermal energy to dissociate, and thus, the glass transition temperature (Tg) of the PEs fall off with an increase in the size of the counteranion. A remarkable conductivity of 2.1 mS/cm was obtained in deionized water when Cl(-) acted as the counteranion. Steric and electronic factors of the counteranion induce a change of transition pH in different PEs, although the chiroptical nature was retained, as confirmed by circular dichroism spectroscopy. PMID:25333268

Narayanan, Amal; Bauri, Kamal; Ruidas, Bhuban; Pradhan, Goutam; Banerjee, Sanjib; De, Priyadarsi

2014-11-11

237

Effects of Hydrogen Peroxide and Ultrasound on Biomass Reduction and Toxin Release in the Cyanobacterium, Microcystis aeruginosa  

PubMed Central

Cyanobacterial blooms are expected to increase, and the toxins they produce threaten human health and impair ecosystem services. The reduction of the nutrient load of surface waters is the preferred way to prevent these blooms; however, this is not always feasible. Quick curative measures are therefore preferred in some cases. Two of these proposed measures, peroxide and ultrasound, were tested for their efficiency in reducing cyanobacterial biomass and potential release of cyanotoxins. Hereto, laboratory assays with a microcystin (MC)-producing cyanobacterium (Microcystis aeruginosa) were conducted. Peroxide effectively reduced M. aeruginosa biomass when dosed at 4 or 8 mg L?1, but not at 1 and 2 mg L?1. Peroxide dosed at 4 or 8 mg L?1 lowered total MC concentrations by 23%, yet led to a significant release of MCs into the water. Dissolved MC concentrations were nine-times (4 mg L?1) and 12-times (8 mg L?1 H2O2) higher than in the control. Cell lysis moreover increased the proportion of the dissolved hydrophobic variants, MC-LW and MC-LF (where L = Leucine, W = tryptophan, F = phenylalanine). Ultrasound treatment with commercial transducers sold for clearing ponds and lakes only caused minimal growth inhibition and some release of MCs into the water. Commercial ultrasound transducers are therefore ineffective at controlling cyanobacteria. PMID:25513892

Lürling, Miquel; Meng, Debin; Faassen, Elisabeth J.

2014-01-01

238

CD3 negative "small agranular lymphocytes" are natural killer cells.  

PubMed

We describe here that CD3-, CD16+ and/or CD56+ small lymphocytes, in a highly reproducible fashion, mediate a significant level of K562 killing that is, on a "per cell" basis, comparable to the cytolytic activity of CD3- LGL. The CD3- small lymphocytes appeared to have no granules based on light and electron microscopy and lack of right-angle scatter on the FACS; we thus refer to them as small "agranular" lymphocytes (SAL). The lytic activity against K562 is inhibited by treatment with either L-leucine methyl ester or EGTA, which are reported to effect granule-dependent killing. We suggest that the SAL have lytic molecules in their cytoplasm (which are sensitive to these treatments) but that these molecules are not organized into discrete granules as found in LGL. The CD3- SAL are phenotypically very similar to LGL and both SAL and LGL mediated equal and reproducible antibody-dependent cell-mediated cytotoxicity. These observations force redefinition of the concept of NK cells to include both CD3- LGL and CD3- SAL. PMID:1827820

Inverardi, L; Witson, J C; Fuad, S A; Winkler-Pickett, R T; Ortaldo, J R; Bach, F H

1991-06-01

239

SerpinB1 is critical for neutrophil survival through cell-autonomous inhibition of cathepsin G.  

PubMed

Bone marrow (BM) holds a large reserve of polymorphonuclear neutrophils (PMNs) that are rapidly mobilized to the circulation and tissues in response to danger signals. SerpinB1 is a potent inhibitor of neutrophil serine proteases neutrophil elastase (NE) and cathepsin G (CG). SerpinB1 deficiency (sB1(-/-)) results in a severe reduction of the BM PMN reserve and failure to clear bacterial infection. Using BM chimera, we found that serpinB1 deficiency in BM cells was necessary and sufficient to reproduce the BM neutropenia of sB1(-/-) mice. Moreover, we showed that genetic deletion of CG, but not NE, fully rescued the BM neutropenia in sB1(-/-) mice. In mixed BM chimera and in vitro survival studies, we showed that CG modulates sB1(-/-) PMN survival through a cell-intrinsic pathway. In addition, membrane permeabilization by lysosomotropic agent l-leucyl-l-leucine methyl ester that allows cytosolic release of granule contents was sufficient to induce rapid PMN death through a CG-dependent pathway. CG-mediated PMN cytotoxicity was only partly blocked by caspase inhibition, suggesting that CG cleaves a distinct set of targets during apoptosis. In conclusion, we have unveiled a new cytotoxic function for the serine protease CG and showed that serpinB1 is critical for maintaining PMN survival by antagonizing intracellular CG activity. PMID:23532733

Baumann, Mathias; Pham, Christine T N; Benarafa, Charaf

2013-05-01

240

Delineation of glutamate pathways and secretory responses in pancreatic islets with ?-cell–specific abrogation of the glutamate dehydrogenase  

PubMed Central

In pancreatic ?-cells, glutamate dehydrogenase (GDH) modulates insulin secretion, although its function regarding specific secretagogues is unclear. This study investigated the role of GDH using a ?-cell–specific GDH knockout mouse model, called ?Glud1?/?. The absence of GDH in islets isolated from ?Glud1–/– mice resulted in abrogation of insulin release evoked by glutamine combined with 2-aminobicyclo[2.2.1]heptane-2-carboxylic acid or l-leucine. Reintroduction of GDH in ?Glud1–/– islets fully restored the secretory response. Regarding glucose stimulation, insulin secretion in islets isolated from ?Glud1–/– mice exhibited half of the response measured in control islets. The amplifying pathway, tested at stimulatory glucose concentrations in the presence of KCl and diazoxide, was markedly inhibited in ?Glud1–/– islets. On glucose stimulation, net synthesis of glutamate from ?-ketoglutarate was impaired in GDH-deficient islets. Accordingly, glucose-induced elevation of glutamate levels observed in control islets was absent in ?Glud1–/– islets. Parallel biochemical pathways, namely alanine and aspartate aminotransferases, could not compensate for the lack of GDH. However, the secretory response to glucose was fully restored by the provision of cellular glutamate when ?Glud1–/– islets were exposed to dimethyl glutamate. This shows that permissive levels of glutamate are required for the full development of glucose-stimulated insulin secretion and that GDH plays an indispensable role in this process. PMID:22875990

Vetterli, Laurène; Carobbio, Stefania; Pournourmohammadi, Shirin; Martin-del-Rio, Rafael; Skytt, Dorte M.; Waagepetersen, Helle S.; Tamarit-Rodriguez, Jorge; Maechler, Pierre

2012-01-01

241

Initial adhesion of Listeria monocytogenes to fine polished stainless steel under flow conditions is determined by prior growth conditions.  

PubMed

Listeria monocytogenes is a food-borne pathogen known to persist in food production environments, where it is able to attach and form biofilms, potentially contaminating food products ready for consumption. In this study the first step in the establishment of L. monocytogenes in a food-processing environment was examined, namely the initial adhesion to stainless steel under specific dynamic flow conditions. It was found that the intrinsic ability of L. monocytogenes to adhere to solid surfaces under flow conditions is dependent on nutrient availability. The addition of L-leucine to the growth medium altered the fatty acid composition of the L. monocytogenes cells and increased adhesion. The growth conditions resulting in the highest adhesion (growth medium with added glucose) had cells with the highest electron donating and lowest electron accepting properties, whereas growth conditions resulting in lowest adhesion (growth medium with added mannose) had cells with the lowest electron donating properties and highest electron accepting properties. The highest and lowest adhesion conditions correlated with differences in expression of cell surface protein of L. monocytogenes and among these the autolysin amidase (Ami). This study implies that food composition influences the adhesion of L. monocytogenes to solid surfaces during dynamic flow conditions. PMID:23685728

Skovager, Anne; Larsen, Marianne Halberg; Castro-Mejia, Josue Leonardo; Hecker, Michael; Albrecht, Dirk; Gerth, Ulf; Arneborg, Nils; Ingmer, Hanne

2013-07-01

242

Acetylene reduction (nitrogen fixation) by enterobacteriaceae isolated from paper mill process waters.  

PubMed

Using selective media containing galactitol, over 130 Enterobacteriaceae have been isolated from paper mill process waters collected from different localities. These bacteria were extensively characterized and tested for acetylene-reducing (nitrogen-fixing) activity under anaerobic conditions. High activity was found in representatives of Klebsiella pneumoniae, Enterobacter aerogenes, Enterobacter cloacae, Erwinia herbicola, Citrobacter freundii, Citrobacter intermedius, and Escherichia coli. Under argon, nitrogenase synthesis was generally not repressed by 5 mM l-glutamate, l-aspartate, l-leucine or Casamino Acids (0.5 g/liter). In many strains, both the specific activities (nanomoles of C(2)H(4) per minute per milligram of protein) and the activities (nanomoles of C(2)H(4) per minute) had considerably declined after 24 h. In three selected strains, activity in intact cells grown under nitrogen was unaffected by the presence during assay of 10 mM l-amino acids or ammonium acetate. All of the strains examined were tolerant towards inactivation of nitrogen-fixing activity by 1.8% (vol/vol) oxygen during assay, and inactivation by up to 10% oxygen was partly reversible. Representatives of the six taxa synthesized nitrogenase in stirred aerobic cultures, though the protein concentrations attained were lower than under anaerobic conditions. It seems reasonable to suggest that under natural conditions, nitrogen fixation is able to contribute significantly to the nitrogen economy of the cells. PMID:16345168

Neilson, A H; Sparell, L

1976-08-01

243

Aminopeptidase-N from the Helicoverpa armigera (Hubner) brush border membrane vesicles as a receptor of Bacillus thuringiensis crylac delta-endotoxin.  

PubMed

Brush border membrane vesicles (BBMVs) were prepared from the 2nd instar larvae of Helicoverpa armigera. Binding of the activated Cry1Ac of Bacillus thuringiensis (Bt) toxin was shown by immunoblot. A 120-kDa protein was identified as a receptor for the Cry1Ac type delta-endotoxin. The aminopeptidase-N activity of BBMVs was measured as the hydrolysis of L-leucine p-nitroanilide. The specific activity was 35 units/mg protein. The BBMV preparation also showed low level of alkaline phosphatase activity. Zn++ chelating agents 2,2'-dipyridyl and 1,10-phenanthroline inhibited aminopeptidase activity at 10 mM concentration, indicating the presence of zinc-dependent aminopeptidase in the brush border of H. armigera. The aminopeptidase activity was increased with increasing concentration of delta-endotoxin. The purified 120-kDa binding protein was N-terminally sequenced. The first 10-amino-acid sequence showed 60-77% similarity with human cysteine-rich secretory protein-1 precursor, inhibin alpha chain precursor. Salmonella flagellar hook protein and yeast carboxypeptidase S. PMID:11683359

Ingle, S S; Trivedi, N; Prasad, R; Kuruvilla, J; Rao, K K; Chhatpar, H S

2001-10-01

244

Glutamine inhibits ammonia-induced accumulation of cGMP in rat striatum limiting arginine supply for NO synthesis.  

PubMed

Brain L-glutamine (Gln) accumulation and increased activity of the NO/cGMP pathway are immediate consequences of acute exposure to ammonia. This study tested whether excess Gln may influence NO and/or cGMP synthesis. Intrastriatal administration of the glutaminase inhibitor 6-diazo-5-oxo-L-norleucine or the system A-specific Gln uptake inhibitor methylaminoisobutyrate increased microdialysate Gln concentration and reduced basal and ammonia-induced NO and cGMP accumulation. Gln applied in vivo (via microdialysis) or in vitro (to rat brain cortical slices) reduced NO and cGMP accumulation in the presence and/or absence of ammonia, but not cGMP synthesis induced by the NO donor sodium nitroprusside. Attenuation of cGMP synthesis by Gln was prevented by administration of L-arginine (Arg). The L-arginine co-substrates of y(+)LAT2 transport system, L-leucine and cyclo-leucine, mimicked the effect of exogenous Gln, suggesting that Gln limits Arg supply for NO synthesis by interfering with y+LAT2-mediated Arg uptake across the cell membrane. PMID:19379813

Hilgier, Wojciech; Fre?ko, Inez; Klemenska, Emilia; Beresewicz, Andrzej; Oja, Simo S; Saransaari, Pirjo; Albrecht, Jan; Zieli?ska, Magdalena

2009-07-01

245

Studies on mass attenuation coefficient, effective atomic number and electron density of some amino acids in the energy range 0.122-1.330 MeV  

NASA Astrophysics Data System (ADS)

The total mass attenuation coefficients of some amino acids, such as Glycine (C2H5NO2), DL-Alanine (C3H7NO2), Proline (C5H9NO2), L-Leucine (C6H13NO2 ), L-Arginine (C6H14N4O2) and L-Arginine Monohydrochloride (C6H15ClN4O2), were measured at 122, 356, 511, 662, 1170, 1275 and 1330 keV photon energies using a well-collimated narrow beam good geometry set-up. The gamma rays were detected using NaI (Tl) scintillation detection system with a resolution of 10.2% at 662 keV. The attenuation coefficient data were then used to obtain the effective atomic numbers (Zeff) and effective electron densities (Neff) of amino acids. It was observed that the effective atomic number (Zeff) and effective electron densities (Neff) tend to be almost constant as a function of gamma-ray energy. The results show that, the experimental values of mass attenuation coefficients, effective atomic numbers and effective electron densities are in good agreement with the theoretical values with less than 1% error.

Pawar, Pravina P.; Bichile, Govind K.

2013-11-01

246

Chiral micellar electrokinetic chromatography (CMEKC)-atmospheric pressure photoionization of benzoin derivatives using mixed molecular micelles  

PubMed Central

In the present work we report, for the first time, the successful on-line coupling of chiral micellar electrokinetic chromatography (CMEKC) to atmospheric pressure photo-ionization mass spectrometry (APPI-MS). Four structurally similar neutral test solutes (e.g., benzoin derivatives) were successfully ionized by APPI-MS. The mass spectra in the positive ion mode showed that the protonated molecular ions of benzoins are not the most abundant fragment ions. Simultaneous enantioseparation by CMEKC and on-line APPI-MS detection of four photoinitiators: hydrobenzoin (HBNZ), benzoin (BNZ), benzoin methyl ether (BME), benzoin ethyl ether (BEE), were achieved using an optimized molar ratio of mixed molecular micelle of two polymeric chiral surfactants (polysodium N-undecenoxy carbonyl-L-leucinate and polysodium N-undecenoyl-L,L-leucylvalinate). The CMEKC conditions, such as voltage, chiral polymeric surfactant concentration, buffer pH, and BGE concentration, were optimized using a multivariate central composite design (CCD). The sheath liquid composition (involving % v/v methanol, dopant concentration, electrolyte additive concentration, and flow rate) and spray chamber parameters (drying gas flow rate, drying gas temperature, and vaporizer temperature) were also optimized with CCD. Models built based on the CCD results and response surface method was used to analyze the interactions between factors and their effects on the responses. The final overall optimum conditions for CMEKC-APPI-MS were also predicted and found in agreement with the experimentally optimized parameters. PMID:21500208

He, Jun; Shamsi, Shahab A.

2012-01-01

247

Synthesis and biological activities of some new (N?-dinicotinoyl)-bis-L-leucyl linear and macrocyclic peptides.  

PubMed

A series of linear and macrocyclic peptides 3-12 were synthesized using 3,5-pyridinedicarboxylic acid (1) as starting material and screened for their antimicrobial, anti-inflammatory and anticancer activities. Bis-ester 3 was prepared from 1 and L-leucine methyl ester. Hydrazinolysis and hydrolysis of dipeptide methyl ester 3 with hydrazine hydrate or 1 N sodium hydroxide afforded compounds 4 and 5, respectively. Cyclization of the dipeptide 5 with L-lysine methyl ester afforded cyclic pentapeptide ester 6. Compounds 7-9 were synthesized by reacting hydrazide 4 with phthalic anhydride, 1,8-naphthalene anhydride or acetophenone derivatives. Treatment of acid hydrazide 4 with aromatic aldehydes or tetraacid dianhydrides afforded the corresponding bis-dipeptide hydrazones 10a-e and macrocyclic peptides 11 and 12, respectively. The structures of newly synthesized compounds were confirmed by IR, 1H-NMR, MS spectral data and elemental analysis. The detailed synthesis, spectroscopic data, biological and pharmacological activities of the synthesized compounds was reported. PMID:25061721

Khayyat, Suzan; Amr, Abd El-Galil

2014-01-01

248

Molecular Dynamics of Peptide Folding at Aqueous Interfaces  

NASA Technical Reports Server (NTRS)

Even though most monomeric peptides are disordered in water they can adopt sequence-dependent, ordered structures, such as a-helices, at aqueous interfaces. This property is relevant to cellular signaling, membrane fusion, and the action of toxins and antibiotics. The mechanism of folding nonpolar peptides at the water-hexane interface was studied in the example of an 11-mer, of poly-L-leucine. Initially placed as a random coil on the water side of the interface, the peptide folded into an a-helix in 36 ns. Simultaneously, the peptide translocated into the hexane side of the interface. Folding was not sequential and involved a 3/10-helix as an intermediate. The folded peptide was either parallel to the interface or had its C-terminus exposed to water. An 11-mer, LQQLLQQLLQL, composed of leucine (L) and glutamine (G), was taken as a model amphiphilic peptide. It rapidly adopted an amphiphilic, disordered structure at the interface. Further folding proceeded through a series of amphiphilic intermediates.

Pohorille, Andrew; Chipot, Christophe; Chang, Sherwood (Technical Monitor)

1997-01-01

249

Engineering of Glarea lozoyensis for Exclusive Production of the Pneumocandin B0 Precursor of the Antifungal Drug Caspofungin Acetate.  

PubMed

Pneumocandins produced by the fungus Glarea lozoyensis are acylated cyclic hexapeptides of the echinocandin family. Pneumocandin B0 is the starting molecule for the first semisynthetic echinocandin antifungal drug, caspofungin acetate. In the wild-type strain, pneumocandin B0 is a minor fermentation product, and its industrial production was achieved by a combination of extensive mutation and medium optimization. The pneumocandin biosynthetic gene cluster was previously elucidated by a whole-genome sequencing approach. Knowledge of the biosynthetic cluster suggested an alternative way to produce exclusively pneumocandin B0. Disruption of GLOXY4, encoding a nonheme, ?-ketoglutarate-dependent oxygenase, confirmed its involvement in l-leucine cyclization to form 4S-methyl-l-proline. The absence of 4S-methyl-l-proline abolishes pneumocandin A0 production, and 3S-hydroxyl-l-proline occupies the hexapeptide core's position 6, resulting in exclusive production of pneumocandin B0. Retrospective analysis of the GLOXY4 gene in a previously isolated pneumocandin B0-exclusive mutant (ATCC 74030) indicated that chemical mutagenesis disrupted the GLOXY4 gene function by introducing two amino acid mutations in GLOXY4. This one-step genetic manipulation can rationally engineer a high-yield production strain. PMID:25527531

Chen, Li; Yue, Qun; Li, Yan; Niu, Xuemei; Xiang, Meichun; Wang, Wenzhao; Bills, Gerald F; Liu, Xingzhong; An, Zhiqiang

2015-03-01

250

Effects of Hydrogen Peroxide and Ultrasound on Biomass Reduction and Toxin Release in the Cyanobacterium, Microcystis aeruginosa.  

PubMed

Cyanobacterial blooms are expected to increase, and the toxins they produce threaten human health and impair ecosystem services. The reduction of the nutrient load of surface waters is the preferred way to prevent these blooms; however, this is not always feasible. Quick curative measures are therefore preferred in some cases. Two of these proposed measures, peroxide and ultrasound, were tested for their efficiency in reducing cyanobacterial biomass and potential release of cyanotoxins. Hereto, laboratory assays with a microcystin (MC)-producing cyanobacterium (Microcystis aeruginosa) were conducted. Peroxide effectively reduced M. aeruginosa biomass when dosed at 4 or 8 mg L-1, but not at 1 and 2 mg L-1. Peroxide dosed at 4 or 8 mg L-1 lowered total MC concentrations by 23%, yet led to a significant release of MCs into the water. Dissolved MC concentrations were nine-times (4 mg L-1) and 12-times (8 mg L-1 H2O2) higher than in the control. Cell lysis moreover increased the proportion of the dissolved hydrophobic variants, MC-LW and MC-LF (where L = Leucine, W = tryptophan, F = phenylalanine). Ultrasound treatment with commercial transducers sold for clearing ponds and lakes only caused minimal growth inhibition and some release of MCs into the water. Commercial ultrasound transducers are therefore ineffective at controlling cyanobacteria. PMID:25513892

Lürling, Miquel; Meng, Debin; Faassen, Elisabeth J

2014-01-01

251

Genomic and metabolomic insights into the natural product biosynthetic diversity of a feral-hog-associated Brevibacillus laterosporus strain.  

PubMed

Bacteria associated with mammals are a rich source of microbial biodiversity; however, little is known concerning the abilities of these microbes to generate secondary metabolites. This report focuses on a bacterium isolated from the ear of a feral hog from southwestern Oklahoma, USA. The bacterium was identified as a new strain (PE36) of Brevibacillus latersporus, which was shown via genomic analysis to contain a large number of gene clusters presumably involved in secondary metabolite biosynthesis. A scale-up culture of B. latersporus PE36 yielded three bioactive compounds that inhibited the growth of methicillin-resistant Staphylococcus aureus (basiliskamides A and B and 12-methyltetradecanoic acid). Further studies of the isolate's secondary metabolome provided both new (auripyrazine) and previously-described pyrazine-containing compounds. In addition, a new peptidic natural product (auriporcine) was purified that was determined to be composed of a polyketide unit, two L-proline residues, two D-leucine residues, one L-leucine residue, and a reduced L-phenylalanine (L-phenylalanol). An examination of the genome revealed two gene clusters that are likely responsible for generating the basiliskamides and auriporcine. These combined genomic and chemical studies confirm that new and unusual secondary metabolites can be obtained from the bacterial associates of wild mammals. PMID:24595070

Theodore, Christine M; Stamps, Blake W; King, Jarrod B; Price, Lauren S L; Powell, Douglas R; Stevenson, Bradley S; Cichewicz, Robert H

2014-01-01

252

Genomic and Metabolomic Insights into the Natural Product Biosynthetic Diversity of a Feral-Hog-Associated Brevibacillus laterosporus Strain  

PubMed Central

Bacteria associated with mammals are a rich source of microbial biodiversity; however, little is known concerning the abilities of these microbes to generate secondary metabolites. This report focuses on a bacterium isolated from the ear of a feral hog from southwestern Oklahoma, USA. The bacterium was identified as a new strain (PE36) of Brevibacillus latersporus, which was shown via genomic analysis to contain a large number of gene clusters presumably involved in secondary metabolite biosynthesis. A scale-up culture of B. latersporus PE36 yielded three bioactive compounds that inhibited the growth of methicillin-resistant Staphylococcus aureus (basiliskamides A and B and 12-methyltetradecanoic acid). Further studies of the isolate's secondary metabolome provided both new (auripyrazine) and previously-described pyrazine-containing compounds. In addition, a new peptidic natural product (auriporcine) was purified that was determined to be composed of a polyketide unit, two L-proline residues, two D-leucine residues, one L-leucine residue, and a reduced L-phenylalanine (L-phenylalanol). An examination of the genome revealed two gene clusters that are likely responsible for generating the basiliskamides and auriporcine. These combined genomic and chemical studies confirm that new and unusual secondary metabolites can be obtained from the bacterial associates of wild mammals. PMID:24595070

Theodore, Christine M.; Stamps, Blake W.; King, Jarrod B.; Price, Lauren S. L.; Powell, Douglas R.; Stevenson, Bradley S.; Cichewicz, Robert H.

2014-01-01

253

Ten novel HMGCL mutations in 24 patients of different origin with 3-hydroxy-3-methyl-glutaric aciduria.  

PubMed

3-Hydroxy-3-methylglutaric aciduria is a rare autosomal recessive genetic disorder that affects ketogenesis and L-leucine catabolism. The clinical acute symptoms include vomiting, convulsions, metabolic acidosis, hypoketotic hypoglycaemia and lethargy. To date, 33 mutations in 100 patients have been reported in the HMGCL gene. In this study 10 new mutations in 24 patients are described. They include: 5 missense mutations: c.109G>A, c.425C>T, c.521G>A, c.575T>C and c.598A>T, 2 nonsense mutations: c.242G>A and c.559G>T, one small deletion: c.853delC, and 2 mutations in intron regions: c.497+4A>G and c.750+1G>A. Two prevalent mutations were detected, 109G>T (E37X) in 38% of disease alleles analyzed and c.504_505delCT in 10% of them. Although patients are mainly of European origin (71%) and mostly Spanish (54%), the group is ethnically diverse and includes, for the first time, patients from Pakistan, Palestine and Ecuador. We also present a simple, efficient method to express the enzyme and we analyze the possible functional effects of missense mutations. The finding that all identified missense mutations cause a >95% decrease in the enzyme activity, indicates that the disease appears only in very severe genotypes." PMID:19177531

Menao, Sebastián; López-Viñas, Eduardo; Mir, Cecilia; Puisac, Beatriz; Gratacós, Esther; Arnedo, María; Carrasco, Patricia; Moreno, Susana; Ramos, Mónica; Gil, María Concepción; Pié, Angeles; Ribes, Antonia; Pérez-Cerda, Celia; Ugarte, Magdalena; Clayton, Peter T; Korman, Stanley H; Serra, Dolors; Asins, Guillermina; Ramos, Feliciano J; Gómez-Puertas, Paulino; Hegardt, Fausto G; Casals, Nuria; Pié, Juan

2009-03-01

254

Strain Improvement of Rhodotorula graminis for Production of a Novel l-Phenylalanine Ammonia-Lyase.  

PubMed

l-Phenylalanine ammonia-lyase (PAL; EC 4.3.1.5) from Rhodotorula rubra has been used in the commercial manufacture of l-phenylalanine from trans-cinnamic acid. In this study, R. graminis PAL was investigated. Mutant strain GX6000 was isolated after ethyl methanesulfonate mutagenesis of wild-type R. graminis GX5007 by selecting for resistance to phenylpropiolic acid, an analog of trans-cinnamic acid. Mutant strain GX6000 produced inducible PAL at levels four- to fivefold higher than had wild-type R. graminis. Furthermore, this strain had several other physiological traits that make it more commercially useful than R. rubra. For example, during fermentation, the PAL half-life was three- to fivefold longer, PAL specific activity was six to seven times higher, and PAL synthesis was significantly less inhibited by temperatures above 30 degrees C. Induction of PAL in strain GX6000 appeared to be less tightly regulated; l-leucine acted synergistically with l-phenylalanine, the physiological inducer, to increase the PAL specific activity and titer to 165 U/g (dry weight) and 3,000 U/liter, respectively, a 40% increase over the effect of l-phenylalanine alone. Strain GX6000 PAL showed significantly greater stability in bioreactors for the synthesis of l-phenylalanine, a finding that is consistent with the stability properties observed during fermentation. PMID:16347620

Orndorff, S A; Costantino, N; Stewart, D; Durham, D R

1988-04-01

255

Strain Improvement of Rhodotorula graminis for Production of a Novel l-Phenylalanine Ammonia-Lyase  

PubMed Central

l-Phenylalanine ammonia-lyase (PAL; EC 4.3.1.5) from Rhodotorula rubra has been used in the commercial manufacture of l-phenylalanine from trans-cinnamic acid. In this study, R. graminis PAL was investigated. Mutant strain GX6000 was isolated after ethyl methanesulfonate mutagenesis of wild-type R. graminis GX5007 by selecting for resistance to phenylpropiolic acid, an analog of trans-cinnamic acid. Mutant strain GX6000 produced inducible PAL at levels four- to fivefold higher than had wild-type R. graminis. Furthermore, this strain had several other physiological traits that make it more commercially useful than R. rubra. For example, during fermentation, the PAL half-life was three- to fivefold longer, PAL specific activity was six to seven times higher, and PAL synthesis was significantly less inhibited by temperatures above 30°C. Induction of PAL in strain GX6000 appeared to be less tightly regulated; l-leucine acted synergistically with l-phenylalanine, the physiological inducer, to increase the PAL specific activity and titer to 165 U/g (dry weight) and 3,000 U/liter, respectively, a 40% increase over the effect of l-phenylalanine alone. Strain GX6000 PAL showed significantly greater stability in bioreactors for the synthesis of l-phenylalanine, a finding that is consistent with the stability properties observed during fermentation. PMID:16347620

Orndorff, Steve A.; Costantino, Nina; Stewart, David; Durham, Don R.

1988-01-01

256

Rational Design and Characterization of D-Phe-Pro-D-Arg-Derived Direct Thrombin Inhibitors  

PubMed Central

The tremendous social and economic impact of thrombotic disorders, together with the considerable risks associated to the currently available therapies, prompt for the development of more efficient and safer anticoagulants. Novel peptide-based thrombin inhibitors were identified using in silico structure-based design and further validated in vitro. The best candidate compounds contained both l- and d-amino acids, with the general sequence d-Phe(P3)-Pro(P2)-d-Arg(P1)-P1?-CONH2. The P1? position was scanned with l- and d-isomers of natural or unnatural amino acids, covering the major chemical classes. The most potent non-covalent and proteolysis-resistant inhibitors contain small hydrophobic or polar amino acids (Gly, Ala, Ser, Cys, Thr) at the P1? position. The lead tetrapeptide, d-Phe-Pro-d-Arg-d-Thr-CONH2, competitively inhibits ?-thrombin's cleavage of the S2238 chromogenic substrate with a Ki of 0.92 µM. In order to understand the molecular details of their inhibitory action, the three-dimensional structure of three peptides (with P1? l-isoleucine (fPrI), l-cysteine (fPrC) or d-threonine (fPrt)) in complex with human ?-thrombin were determined by X-ray crystallography. All the inhibitors bind in a substrate-like orientation to the active site of the enzyme. The contacts established between the d-Arg residue in position P1 and thrombin are similar to those observed for the l-isomer in other substrates and inhibitors. However, fPrC and fPrt disrupt the active site His57-Ser195 hydrogen bond, while the combination of a P1 d-Arg and a bulkier P1? residue in fPrI induce an unfavorable geometry for the nucleophilic attack of the scissile bond by the catalytic serine. The experimental models explain the observed relative potency of the inhibitors, as well as their stability to proteolysis. Moreover, the newly identified direct thrombin inhibitors provide a novel pharmacophore platform for developing antithrombotic agents by exploring the conformational constrains imposed by the d-stereochemistry of the residues at positions P1 and P1?. PMID:22457833

Zakia, Sheuli; Gingold, Julian; Philipp, Manfred; Pereira, Pedro J. B.

2012-01-01

257

Amino acid prodrug of quinidine: an approach to circumvent P-glycoprotein mediated cellular efflux.  

PubMed

In the present study, we investigated the effect of large neutral amino acid modification in overcoming P-gp mediated cellular efflux of quinidine. L-isoleucine ester prodrug of quinidine (Ile-quinidine) was synthesized in our laboratory. [14C]-erythromycin was selected as a model substrate to study interaction of quinidine and Ile-quinidine with P-gp. Transport studies were conducted to study translocation kinetics of quinidine and Ile-quinidine in MDCK-MDR1 cells. In cellular accumulation study, uptake rate of [14C]-erythromycin elevated drastically in presence of cyclosporine A and GF 120918. This result indicates that [14C]-erythromycin is an excellent substrate of P-gp. Similarly, uptake rate of [14C]-erythromycin was enhanced significantly in presence of quinidine (25 and 50 ?M). However, [14C]-erythromycin uptake rate remained fairly constant in presence of Ile-quinidine (25 ?M). Apparent A-B and B-A permeability of quinidine observed in MDCK-MDR1 cells were 1.6 ± 0.2 × 10(-6) and 7.0 ± 0.4 × 10(-6)cm/s, a 4.4-fold difference. Moreover, A-B permeability of quinidine increased dramatically in the presence of cyclosporine A and GF 120918. Apparent permeability values of Ile-quinidine observed from A-B and B-A direction were 4.3 ± 0.9 × 10(-6) and 5.5 ± 0.4 × 10(-6)cm/s, a 1.3-fold difference. Importantly, A-B transport of Ile-quinidine did not change dramatically in the presence of cyclosporine and GF 120918. Based on these results, it was apparent that quinidine displayed higher substrate affinity toward P-gp relative to Ile-quinidine. Chemical or enzymatic hydrolysis of Ile-quinidine resulted in regeneration of low quantities of quinidine during transport studies. Competitive inhibition studies demonstrated that Ile-quinidine was recognized by multiple amino acid transporters such as LAT1, LAT2 and cationic amino acid transporter. In conclusion, chemical modification of quinidine with neutral amino acids results in circumvention of P-gp mediated drug efflux. Hence, amino acid transporter targeted prodrug delivery seems to be a viable strategy for improving drug accumulation in P-gp overexpressing cells. PMID:24440401

Patel, Mitesh; Mandava, Nanda K; Pal, Dhananjay; Mitra, Ashim K

2014-04-10

258

Chemical and Enzymatic Stability of Amino acid Prodrugs Containing Methoxy, Ethoxy and Propylene Glycol Linkers  

PubMed Central

Purpose To evaluate the chemical and enzymatic stabilities of methoxy, ethoxy and propylene glycol linker containing prodrugs in order to find a suitable linker for prodrugs of carboxylic acids with amino acids. Methods L-valine and L-phenylalanine prodrugs of model compounds (benzoic acid and phenyl acetic acid) containing methoxy, ethoxy and propylene glycol linkers were synthesized. The hydrolysis rate profile of each compound was studied at physiologically relevant pHs (1.2, 4, 6 and 7.4). Enzymatic hydrolysis of propylene glycol containing compounds was studied using Caco-2 homogenate as well as purified enzymes, valacyclovirase. Results It was observed that the stability of the prodrugs increases with the linker length (propyl>ethyl>methyl). The model prodrugs were stable at acidic pH as compared to basic pH. It was observed that the prodrug with the aliphatic amino acid promoiety was more stable as compared to its aromatic counterpart. The comparison between benzyl and the phenyl model compounds revealed that the amino acid side chain is significant in determining the stability of the prodrug whereas the benzyl or phenyl carboxylic acid had little or no effect on the stability. The enzymatic activation studies of propylene glycol linker prodrug in presence of valacyclovirase and cell homogenate showed faster generation of the parent drug at pH 7.4. The half life of prodrugs at pH 7.4 was more than 12 hours, whereas in presence of cell homogenate the half lives were less than 1 hour. Hydrolysis by Caco-2 homogenate generated the parent compound in two steps, where the prodrug was first converted to the intermediate, propylene glycol benzoate, which was then converted to the parent compound (benzoic acid). Enzymatic hydrolysis of propylene glycol containing prodrugs by valacyclovirase showed hydrolysis of the amino acid ester part to generate the propylene glycol ester of model compound (propylene glycol benzoate) as the major product. Conclusion The methoxy linker containing amino acid prodrugs were the least stable while propylene glycol linker containing prodrugs were most stable. This work suggests that the propylene glycol linker is an optimal linker for amino acids prodrugs since it has good chemical stability and is enzymatically hydrolyzed to yield the parent drug. This approach can be further extended to other non-amino acid prodrugs and to provide a chemical handle to modify lead molecules containing carboxylic group(s). PMID:19566080

Gupta, Deepak; Gupta, Sheeba Varghese; Lee, Kyung-Dall; Amidon, Gordon L.

2012-01-01

259

Global regulation of food supply by Pseudomonas putida DOT-T1E.  

PubMed

Pseudomonas putida DOT-T1E was used as a model to develop a "phenomics" platform to investigate the ability of P. putida to grow using different carbon, nitrogen, and sulfur sources and in the presence of stress molecules. Results for growth of wild-type DOT-T1E on 90 different carbon sources revealed the existence of a number of previously uncharted catabolic pathways for compounds such as salicylate, quinate, phenylethanol, gallate, and hexanoate, among others. Subsequent screening on the subset of compounds on which wild-type DOT-TIE could grow with four knockout strains in the global regulatory genes Deltacrc, Deltacrp, DeltacyoB, and DeltaptsN allowed analysis of the global response to nutrient supply and stress. The data revealed that most global regulator mutants could grow in a wide variety of substrates, indicating that metabolic fluxes are physiologically balanced. It was found that the Crc mutant did not differ much from the wild-type regarding the use of carbon sources. However, certain pathways are under the preferential control of one global regulator, i.e., metabolism of succinate and d-fructose is influenced by CyoB, and l-arginine is influenced by PtsN. Other pathways can be influenced by more than one global regulator; i.e., l-valine catabolism can be influenced by CyoB and Crp (cyclic AMP receptor protein) while phenylethylamine is affected by Crp, CyoB, and PtsN. These results emphasize the cross talk required in order to ensure proper growth and survival. With respect to N sources, DOT-T1E can use a wide variety of inorganic and organic nitrogen sources. As with the carbon sources, more than one global regulator affected growth with some nitrogen sources; for instance, growth with nucleotides, dipeptides, d-amino acids, and ethanolamine is influenced by Crp, CyoB, and PtsN. A surprising finding was that the Crp mutant was unable to flourish on ammonium. Results for assayed sulfur sources revealed that CyoB controls multiple points in methionine/cysteine catabolism while PtsN and Crc are needed for N-acetyl-l-cysteamine utilization. Growth of global regulator mutants was also influenced by stressors of different types (antibiotics, oxidative agents, and metals). Overall and in combination with results for growth in the presence of various stressors, these phenomics assays provide multifaceted insights into the complex decision-making process involved in nutrient supply, optimization, and survival. PMID:20139187

Daniels, Craig; Godoy, Patricia; Duque, Estrella; Molina-Henares, M Antonia; de la Torre, Jesús; Del Arco, José María; Herrera, Carmen; Segura, Ana; Guazzaroni, M Eugenia; Ferrer, Manuel; Ramos, Juan Luis

2010-04-01

260

3H-L-histidine and 65Zn(2+) are cotransported by a dipeptide transport system in intestine of lobster Homarus americanus.  

PubMed

The tubular intestine of the American lobster Homarus americanus was isolated in vitro and perfused with a physiological saline whose composition was based on hemolymph ion concentrations and contained variable concentrations of (3)H-l-histidine, (3)H-glycyl-sarcosine and (65)Zn(2+). Mucosa to serosa (M-->S) flux of each radiolabelled substrate was measured by the rate of isotope appearance in the physiological saline bathing the tissue on the serosal surface. Addition of 1-50 micromol l(-1) zinc to the luminal solution containing 1-50 micromol l(-1) (3)H-l-histidine significantly (P<0.01) increased M-->S flux of amino acid compared to controls lacking the metal. The kinetics of M-->S (3)H-l-histidine flux in the absence of zinc followed Michaelis-Menten kinetics (K(m)=6.2+/-0.8 micromol l(-1); J(max) =0.09+/-0.004 pmol cm(-2) min(-1)). Addition of 20 micromol l(-1) zinc to the luminal perfusate increased both kinetic constants (K(m)=19+/-3 micromol l(-1); J(max)=0.28+/-0.02 pmol cm(-2) min(-1)). Addition of both 20 micromol l(-1) zinc and 100 micromol l(-1) l-leucine abolished the stimulatory effect of the metal alone (K(m)=4.5+/-1.7 micromol l(-1); J(max)=0.08+/-0.008 pmol cm(-2) min(-1)). In the absence of l-histidine, M-->S flux of (65)Zn(2+) also followed the Michaelis-Menten relationship and addition of l-histidine to the perfusate significantly (P<0.01) increased both kinetic constants. Addition of either 50 micromol l(-1) Cu(+) or Cu(2+) and 20 micromol l(-1) l-histidine simultaneously abolished the stimulatory effect of l-histidine alone on transmural (65)Zn(2+) transport. Zinc-stimulation of M-->S (3)H-l-histidine flux was significantly (P<0.01) reduced by the addition of 100 micromol l(-1) glycyl-sarcosine to the perfusate, as a result of the dipeptide significantly (P<0.01) reducing both l-histidine transport K(m) and J(max). Transmural transport of (3)H-glycyl-sarcosine was unaffected by the presence of either l-histidine or l-leucine when either amino acid was added to the perfusate alone, but at least a 50% reduction in peptide transport was observed when zinc and either of the amino acids were added simultaneously. These results show that (3)H-l-histidine and (65)Zn(2+) are cotransported across the lobster intestine by a dipeptide carrier protein that binds both substrates in a bis-complex (Zn-[His](2)) resembling the normal dipeptide substrate. In addition, the transmural transports of both substrates may also occur by uncharacterized carrier processes that are independent of one another and appear relatively specific to the solutes used in this study. PMID:15634848

Conrad, Erik M; Ahearn, Gregory A

2005-01-01

261

The `neurotoxicity' of l-2,4-diaminobutyric acid  

PubMed Central

The neurolathyrogen l-2,4-diaminobutyric acid is concentrated by liver, and liver damage can yield neurotoxicity; thus the neurotoxicity caused by this compound may be due to liver damage followed by secondary brain damage. 1. The intraperitoneal administration of toxic doses of l-2,4-diaminobutyric acid to rats resulted in hyperirritability, tremors and convulsions in 12–20hr. and increased the concentration of ammonia of blood and brain slightly and the concentration of glutamine of brain two- to three-fold. By contrast, toxic doses of l-homoarginine, l-lysine, l-leucine and ammonium acetate caused dyspnoea, extreme prostration, and in some cases coma in 15–30min., and increased the concentration of ammonia of blood significantly and the concentration of glutamine of brain slightly. These results indicate that l-2,4-diaminobutyric acid caused a chronic ammonia toxicity, whereas the other amino acids and ammonium acetate resulted in an acute ammonia toxicity. 2. Liver slices from l-2,4-diaminobutyric acid-treated animals and normal liver slices preincubated with l-2,4-diaminobutyric acid utilized ammonia and formed urea at a lower rate than control slices from normal rats. 3. l-2,4-Diaminobutyric acid inhibited competitively ornithine carbamoyltransferase of rat liver homogenates, thus demonstrating that this reaction is a primary site of toxicity for this neurolathyrogen. Although we were unable to show marked elevations of blood ammonia concentration after treatment with l-2,4-diaminobutyric acid, these results are interpreted to mean that ammonia utilization (urea synthesis) in liver is inhibited by l-2,4-diaminobutyric acid and that at least part of the neurotoxicity is due to a prolonged slight increase in body ammonia concentration. PMID:5639925

O'Neal, Robert M.; Chen, Chung-Ho; Reynolds, Carol S.; Meghal, Sharadchandra K.; Koeppe, Roger E.

1968-01-01

262

Activation of autophagy by rapamycin does not protect oligodendrocytes against protein aggregate formation and cell death induced by proteasomal inhibition.  

PubMed

Pathological protein inclusions containing the microtubule-associated protein tau, ubiquitin, and a variety of heat shock proteins, originating in oligodendrocytes, are consistent features observed in a number of neurodegenerative diseases. Defects in the proteolytic degradation systems have been associated with protein aggregate formation. The ubiquitin proteasome system (UPS) and autophagy are critically involved in the maintenance of cellular homeostasis and their activities need to be carefully balanced. A genuine crosstalk exists between the UPS and the autophagosomal system, and when the UPS is impaired, autophagy might act as a compensatory mechanism. Autophagy represents a lysosomal degradation system for degrading long-lived proteins and organelles, including damaged mitochondria. As we have shown before, proteasomal impairment by the reversible proteasomal inhibitor MG-132 (carbobenzoxy-L-leucyl-L-leucyl-L-leucinal) in oligodendrocytes leads to protein aggregate formation and apoptotic cell death, caused by activation of caspases and the mitochondrial pathway. The present study was undertaken to elucidate whether upregulation of the autophagic pathway by rapamycin can protect oligodendrocytes and ameliorate the consequences of MG-132-induced protein aggregate formation. The data show that rapamycin attenuated the formation of dense protein aggregates, but did not enhance the survival capability of oligodendrocytes after proteasomal inhibition. After activation of the autophagic pathway in combination with proteasomal inhibition, caspase 3 activation and poly(ADP-ribose) polymerase-1 cleavage were even more pronounced than after proteasomal inhibition alone. Furthermore, rapamycin augmented MG-132-induced activation of extracellular signal-regulated kinases 1 and 2, which are involved in the regulation of cell death and survival. In summary, depending on the cellular context and system, rapamycin may promote cell survival or, under other conditions in concert with apoptosis, may augment cell death, which seems to be the case in oligodendrocytes. Its therapeutic use for neurodegenerative disorders is most likely limited, since long-term administration may impair neuronal survival and specifically damage the myelin forming cells of the CNS. PMID:25069858

Noack, Monika; Richter-Landsberg, Christiane

2015-01-01

263

The proteasome inhibitor bortezomib reduced cholesterol accumulation in fibroblasts from Niemann-Pick type C patients carrying missense mutations.  

PubMed

Niemann-Pick disease type C (NPC) is a lipid storage disorder mainly caused by mutations in the NPC1 gene. Approximately 60% of these mutations are missense changes that may induce reduced NPC1 protein levels by increased degradation via ubiquitin-proteasome. This is the case for the most prevalent worldwide mutation, p.Ile1061Thr, as well as for other three missense changes. In the present study, we analyzed the NPC1 levels in fibroblasts from eighteen NPC patients presenting missense mutations. We found that fourteen of these cells lines showed decreased levels of NPC1. Six of these cell lines were homozygous, whereas the other eight were associated with a frame shifting mutation. We focused our attention in the NPC homozygous samples and demonstrated that, in most of the cases, NPC1 reduction was a consequence of a decrease of its half-life. NPC cells were treated not only with the proteasome inhibitors carbobenzoxy-l-leucyl-l-leucyl-l-leucinal or N-acetyl-leucyl-leucyl-norleucinal, both widely used as a research tools, but also with bortezomib, the first proteasome inhibitor to reach clinical applications, although it has never been used in NPC disease. We observed that, after treatment, the mutant NPC1 protein levels were partially recovered in most of the cell lines. Importantly, these mutant proteins partially recovered their activity and substantially reduced free cholesterol levels. These results suggest that by enhancing the NPC1 protein stability with the use of proteasome inhibitors, their functionality might be recovered and this might represent a therapeutical approach for future treatments of NPC disease resulting from specific missense mutations. PMID:25131710

Macías-Vidal, Judit; Girós, Marisa; Guerrero, Martina; Gascón, Pere; Serratosa, Joan; Bachs, Oriol; Coll, Maria Josep

2014-10-01

264

Allocation of endogenous and dietary protein in the reconstitution of the gastrointestinal tract in migratory blackcaps at stopover sites.  

PubMed

During migratory flight, the mass of the gastrointestinal tract (GIT) and its associated organs in small birds decreases in size by as much as 40%, compared with the preflight condition because of the catabolism of protein. At stopover sites, birds need 2-3 days to rebuild their GIT so that they can restore body mass and fat reserves to continue migration. The source of protein used to rebuild the GIT may be exogenous (from food ingested) or endogenous (reallocated from other organs) or both. Because the relative contribution of these sources to rebuild the GIT of migratory birds is not yet known, we mimicked in-flight fasting and then re-feeding in two groups of blackcaps (Sylvia atricapilla), a Palearctic migratory passerine. The birds were fed a diet containing either 3% or 20% protein to simulate different refueling scenarios. During re-feeding, birds received known doses of (15)N-(l)-leucine before we measured the isotope concentrations in GIT and associated digestive organs and in locomotory muscles. We then quantified the extent to which blackcaps rebuilt their GIT with endogenous and/or dietary protein while refeeding after a fast. Our results indicate that blackcaps fed the low-protein diet incorporated less exogenous nitrogen into their tissues than birds fed the 20% protein diet. They also allocated relatively more exogenous protein to the GIT than to pectoral muscle than those birds re-fed with the high-protein diet. However, this compensation was not sufficient for birds eating the low-protein diet to rebuild their intestine at the same rate as the birds re-fed the high-protein diet. We concluded that blackcaps must choose stopover sites at which they can maximize protein intake to minimize the time it takes to rebuild their GIT and, thus, resume migration as soon as possible. PMID:22399651

Muñoz-Garcia, Agustí; Aamidor, Sarah E; McCue, Marshall D; McWilliams, Scott R; Pinshow, Berry

2012-04-01

265

[Effects of applying different kind fertilizers on enzyme activities related to carbon, nitrogen, and phosphorus cycles in reddish paddy soil].  

PubMed

Based on the long-term fixed position experimental data from Qianyanzhou Ecological Experiment Station, Chinese Academy of Sciences in 1998, this paper analyzed the effects of applying different kind fertilizers (straw, ST; pig manure, OM; and chemical fertilizer, NPK) on the nutrients (C, N, and P) status and the activities of related enzymes ( beta-1,4-glucosidase, betaG; beta-1,4-N-acetylglucosaminidase, NAG; L-leucine aminopeptidase, LAP; and acid phosphatase, AP) in reddish paddy soil. With the application of OM, the activities of soil betaG, NAG, and LAP increased significantly, as compared with other treatments, and were 1.4, 2. 6, and 1.9 times higher than the control (CK) , respectively. Applying OM also improved the ratio of soil organic carbon to total nitrogen (C/N), but decreased the soil betaG/(NAG+LAP) ratio, suggesting that pig manure could benefit the degradation of soil cellulose and the accumulation of soil organic carbon. Applying NPK increased the activities of soil betaG, NAG, and LAP, but decreased the AP activity, with a decrement of 34% as compared with CK. Under the application of NPK, the soilbetaG/AP and (NAG+ LAP)/AP ratios increased, but the ratios of soil organic carbon to total phosphorus (C/P) and of soil total nitrogen to total phosphorus (N/P) decreased, indicating that chemical fertilizers could induce the accumulation of soil inorganic phosphorus, and inhibit the microbial functions of degrading polysaccharides and phosphate phospholipids. PMID:23898644

Xu, Li-Li; Wang, Qiu-Bing; Zhang, Xin-Yu; Sun, Xiao-Min; Dai, Xiao-Qin; Yang, Feng-Ting; Bu, Jin-Feng; Wang, Hui-min

2013-04-01

266

Pulmonary immunization of guinea pigs with diphtheria CRM-197 antigen as nanoparticle aggregate dry powders enhance local and systemic immune responses.  

PubMed

This study establishes the immune response elicited in guinea pigs after pulmonary and parenteral immunizations with diphtheria CRM-197 antigen (CrmAg). Several spray-dried powders of formalin-treated/untreated CrmAg nanoaggregates with L-leucine were delivered to the lungs of guinea pigs. A control group consisting of alum with adsorbed CrmAg in saline was administered by intramuscular injection. Animals received three doses of powder vaccines containing 20 or 40 ?g of CrmAg. The serum IgG titers were measured for 16 weeks after the initial immunization; IgA titers were measured at the time of sacrifice in the broncho-alveolar lavage fluid. Further, toxin neutralization tests in naïve guinea pigs were performed for a few select serum samples. Histopathology of the lung tissues was conducted to evaluate inflammation or injury to the lung tissues. While the highest titer of serum IgG antibody was observed in guinea pigs immunized by the intramuscular route, those animals immunized with dry powder formulation by the pulmonary route, and without the adjuvant alum, exhibited high IgA titers. A pulmonary administered dry powder, compared to parenteral immunization, conferred complete protection in the toxin neutralization test. Mild inflammation was observed in lung tissues of animals receiving dry powder vaccines by the pulmonary route. Thus, administering novel CrmAg as dry powders to the lungs may be able to overcome some of the disadvantages observed with the existing diphtheria vaccine which is administered by the parenteral route. In addition, these powders will have the advantage of eliciting a high mucosal immune response in the lungs without using traditional adjuvants. PMID:20878294

Muttil, Pavan; Pulliam, Brian; Garcia-Contreras, Lucila; Fallon, John Kevin; Wang, Chenchen; Hickey, Anthony James; Edwards, David A

2010-12-01

267

Bacterial translocation is reduced by a specific nutritional combination in mice with chemotherapy-induced neutropenia.  

PubMed

Immune function is compromised in many cancer patients, leading to an increased risk of (infectious) complications. Chemotherapy-induced neutropenia is a common cause of treatment-induced immune suppression. In the present study, the effect of a specific nutritional combination (SNC) on bacterial translocation was studied in a model of chemotherapy-induced neutropenia in C3H/HeN mice colonized with Pseudomonas aeruginosa PAO-1. Dietary intervention started after stable colonization with P. aeruginosa to compare the SNC containing high protein, l-leucine, fish oil, and specific oligosaccharides to an isoenergetic control diet. After 3 wk, the mice were treated with cyclophosphamide to induce neutropenia. This rendered the mice susceptible to Pseudomonas translocation, which was quantified 5 d later. Intervention with the SNC resulted in a reduced incidence and intensity of bacterial translocation to the liver (P < 0.05) and a similar trend in the lungs (P ? 0.057). In addition, the SNC reduced the fecal pH (P < 0.05) and decreased P. aeruginosa counts in fecal samples (P < 0.05). Moreover, plasma concentrations of proinflammatory cytokines were correlated with the reduced bacterial translocation to the liver (? > 0.78; P < 0.001). In conclusion, dietary intervention with the SNC significantly reduced the incidence and severity of P. aeruginosa translocation in a mouse model of chemotherapy-induced immune suppression. Several mechanisms might have played a role, including the modulation of the intestinal microbiota, an improved gut barrier function, immune function, and a reduced inflammatory state. These results suggest an opportunity to develop new applications in cancer patients, with the aim to reduce infectious and other complications. PMID:21562235

Faber, Joyce; van Limpt, Kees; Kegler, Diane; Luiking, Yvette; Garssen, Johan; van Helvoort, Ardy; Vos, Arjan Paul; Knol, Jan

2011-07-01

268

Homocysteine, a risk factor for atherosclerosis, biphasically changes the endothelial production of kynurenic acid.  

PubMed

Increased serum level of homocysteine is an independent risk factor for vascular disease. The effect of DL-homocysteine on the endothelial production of kynurenic acid, an antagonist of alpha7-nicotinic and N-methyl-D-aspartate (NMDA) glutamate receptors, has been evaluated in vitro and in vivo. In rat aortic rings, DL-homocysteine at 40-100 microM enhanced, whereas at >or=400 microM decreased the synthesis of kynurenic acid. S-adenosylhomocysteine mimicked the biphasic action of DL-homocysteine. On the contrary, thiol-containing compounds, L-cysteine and L-methionine, were only inhibiting kynurenic acid production. L-kynurenine uptake blockers, L-phenylalanine and L-leucine, reversed the stimulatory effect of S-adenosylhomocysteine. L-glycine, co-agonist of NMDA receptor, and cis-4-phosphonomethyl-2-piperidine carboxylic acid (CGS 19755), an antagonist of NMDA receptor, have not influenced kynurenic acid formation. In vivo, DL-homocysteine (1.3 mmol, i.p.) increased the level of kynurenic acid in rat serum from 23.7+/-7.1 to 60.7+/-14.2 (15 min, P<0.01) and 55.7+/-13.6 (60 min, P<0.01) pmol/ml, respectively; the endothelial content of kynurenic acid was also increased (51.6+/-5.8 vs. 73.2+/-9.4 fmol/microg of protein; 15 min; P<0.01). DL-homocysteine seems to modulate the production of kynurenic acid both directly and indirectly, possibly following the conversion to S-adenosylhomocysteine. The obtained data suggest a potential contribution of altered formation of kynurenic acid to the endothelial changes induced by hyperhomocysteinemia. PMID:15961072

Stazka, Janusz; Luchowski, Piotr; Urbanska, Ewa M

2005-07-11

269

Myocardial Oxidative Metabolism and Protein Synthesis during Mechanical Circulatory Support by Extracorporeal Membrane Oxygenation  

SciTech Connect

Extracorporeal membrane oxygenation (ECMO) provides mechanical circulatory support essential for survival in infants and children with acute cardiac decompensation. However, ECMO also causes metabolic disturbances, which contribute to total body wasting and protein loss. Cardiac stunning can also occur which prevents ECMO weaning, and contributes to high mortality. The heart may specifically undergo metabolic impairments, which influence functional recovery. We tested the hypothesis that ECMO alters oxidative. We focused on the amino acid leucine, and integration with myocardial protein synthesis. We used a translational immature swine model in which we assessed in heart (i) the fractional contribution of leucine (FcLeucine) and pyruvate (FCpyruvate) to mitochondrial acetyl-CoA formation by nuclear magnetic resonance and (ii) global protein fractional synthesis (FSR) by gas chromatography-mass spectrometry. Immature mixed breed Yorkshire male piglets (n = 22) were divided into four groups based on loading status (8 hours of normal circulation or ECMO) and intracoronary infusion [13C6,15N]-L-leucine (3.7 mM) alone or with [2-13C]-pyruvate (7.4 mM). ECMO decreased pulse pressure and correspondingly lowered myocardial oxygen consumption (~ 40%, n = 5), indicating decreased overall mitochondrial oxidative metabolism. However, FcLeucine was maintained and myocardial protein FSR was marginally increased. Pyruvate addition decreased tissue leucine enrichment, FcLeucine, and Fc for endogenous substrates as well as protein FSR. Conclusion: The heart under ECMO shows reduced oxidative metabolism of substrates, including amino acids, while maintaining (i) metabolic flexibility indicated by ability to respond to pyruvate, and (ii) a normal or increased capacity for global protein synthesis, suggesting an improved protein balance.

Priddy, MD, Colleen M.; Kajimoto, Masaki; Ledee, Dolena; Bouchard, Bertrand; Isern, Nancy G.; Olson, Aaron; Des Rosiers, Christine; Portman, Michael A.

2013-02-01

270

Efficient fermentation of an improved synthetic grape must by enological and laboratory strains of Saccharomyces cerevisiae  

PubMed Central

Grape must or freshly pressed grape juice is a complex chemical matrix that impacts the efficiency of yeast fermentation. The composition of natural grape must (NGM) can be variable; thus, to ensure reproducibility, a synthetic grape must (SGM) with defined composition is commonly used. The aim of this work was to create conditions to advance the use of Saccharomyces cerevisiae laboratory strains for wine fermentation studies, considering previous results obtained for enological strains fermenting NGM under simulated winery conditions. We designed a new SGM formulation, ISA-SGM, by introducing specific modifications to a commonly used formulation, putting together previous reports. We added glucose and fructose in equal amounts (125 g/l) and 50 parts per million (ppm) sulfur dioxide (SO2, corresponding to standard enological treatment), and we optimized the concentrations of malic acid (3 g/l), citric acid (0.3 g/l), and tartaric acid (3 g/l). Using ISA-SGM, we obtained similar fermentative profiles for the wine strain ISA1000, the prototrophic strain S288C, and its auxotrophic derivative BY4741. In this case, the concentrations of supplements were optimized to 120 mg/l L-uracil, 80 mg/l L-methionine, 400 mg/l L-leucine, and 100 mg/l L-histidine. All these strains tested in ISA-SGM presented a similar fermentative performance as ISA1000 in NGM. ISA-SGM formulation is a promising new tool to allow the use of the auxotrophic BY strains in the detailed assessment of the alcoholic fermentation process under simulated winery conditions, and it provides a foundation to extract relevant physiological conclusions in future research on enological yeast traits. PMID:24949253

2014-01-01

271

Leucine and glucose turnover in chronic alcoholics during early abstinence and after an ethanol load.  

PubMed

We studied leucine turnover using a primed infusion of [1-14C]-L-leucine and glucose turnover using a primed infusion of [6-3H]-D-glucose in five alcoholic patients without liver damage and five age-matched controls. Infusions were maintained for 6 hr, and at the end of the 3rd hour, a 0.8 g/kg iv ethanol load was administered in 20 min. Leucine flux, nonoxidative disposal and oxidation rates, and glucose rate of appearance were calculated during the 3rd and 6th hours of infusion. Ethanol disappearance rate and the percentage completely metabolized to CO2 and H2O in 3 hr were also calculated. Compared with controls, alcoholics had significantly higher basal leucine flux (55.6 +/- 12 vs. 37.3 +/- 9.3 microM/m2/min) and nonoxidative disposal (48.7 +/- 8.7 vs. 31.1 +/- 7.5 microM/m2/min). No differences were observed in basal glucose appearance rates in alcoholics and controls (397.6 +/- 115.2 vs. 349.4 +/- 120.6 microM/m2/min). Compared with controls, alcoholics had a higher alcohol disappearance rate (2.72 +/- 0.59 vs. 1.84 +/- 0.43 mM/kg/min) and percentage of ethanol metabolized to CO2 and H2O in 3 hr (40.6 +/- 10.2 vs. 22.9 +/- 6.9%). After the ethanol load, both leucine turnover and glucose rate of appearance decreased significantly only in alcoholics. There was a positive correlation between the change in leucine flux and ethanol disappearance rate and percentage metabolized to CO2 and H2O in alcoholics. PMID:8116845

Petermann, M; González, C; Hirsch, S; Pía de la Maza, M; Bunout, D

1993-12-01

272

Cloning and characterization of a novel fold-type I branched-chain amino acid aminotransferase from the hyperthermophilic archaeon Thermococcus sp. CKU-1.  

PubMed

We successfully cloned a novel branched-chain amino acid aminotransferase (Ts-BcAT; EC 2.6.1.42) gene from the Thermococcus sp. CKU-1 genome and expressed it in the soluble fraction of Escherichia coli Rosetta (DE3) cells. Ts-BcAT is a homodimer with an apparent molecular mass of approximately 92 kDa. The primary structure of Ts-BcAT showed high homology with the fold-type I, subgroup I aminotransferases, but showed little homology with BcATs known to date, i.e., those of Escherichia coli and Salmonella typhimurium, which belong to the fold-type IV, subgroup III aminotransferases. The maximum enzyme activity of Ts-BcAT was detected at 95 °C, and Ts-BcAT did not lose any enzyme activity, even after incubation at 90 °C for 5 h. Ts-BcAT was active in the pH range from 4.0 to 11.0, the optimum pH was 9.5, and the enzyme was stable between pH 6 and 7. The exceptionally low pK a of the nitrogen atom in the Lys258 ?-amino group in the internal aldimine bond of Ts-BcAT was determined to be 5.52 ± 0.05. Ts-BcAT used 21 natural and unnatural amino acids as a substrate in the overall transamination reaction. L-Leucine and other aliphatic amino acids are efficient substrates, while polar amino acids except glutamate were weak substrates. Phylogenetic analysis revealed that Ts-BcAT is a novel fold-type I, subgroup I branched-chain aminotransferase. PMID:24687296

Uchida, Yuki; Hayashi, Hideyuki; Washio, Tsubasa; Yamasaki, Ryo; Kato, Shiro; Oikawa, Tadao

2014-05-01

273

Myocardial Reloading After Extracorporeal Membrane Oxygenation Alters Substrate Metabolism While Promoting Protein Synthesis  

PubMed Central

Background Extracorporeal membrane oxygenation (ECMO) unloads the heart, providing a bridge to recovery in children after myocardial stunning. ECMO also induces stress which can adversely affect the ability to reload or wean the heart from the circuit. Metabolic impairments induced by altered loading and/or stress conditions may impact weaning. However, cardiac substrate and amino acid requirements upon weaning are unknown. We assessed the hypothesis that ventricular reloading with ECMO modulates both substrate entry into the citric acid cycle (CAC) and myocardial protein synthesis. Methods and Results Sixteen immature piglets (7.8 to 15.6 kg) were separated into 2 groups based on ventricular loading status: 8?hour ECMO (UNLOAD) and postwean from ECMO (RELOAD). We infused into the coronary artery [2?13C]?pyruvate as an oxidative substrate and [13C6]?L?leucine as an indicator for amino acid oxidation and protein synthesis. Upon RELOAD, each functional parameter, which were decreased substantially by ECMO, recovered to near?baseline level with the exclusion of minimum dP/dt. Accordingly, myocardial oxygen consumption was also increased, indicating that overall mitochondrial metabolism was reestablished. At the metabolic level, when compared to UNLOAD, RELOAD altered the contribution of various substrates/pathways to tissue pyruvate formation, favoring exogenous pyruvate versus glycolysis, and acetyl?CoA formation, shifting away from pyruvate decarboxylation to endogenous substrate, presumably fatty acids. Furthermore, there was also a significant increase of tissue concentrations for all CAC intermediates (?80%), suggesting enhanced anaplerosis, and of fractional protein synthesis rates (>70%). Conclusions RELOAD alters both cytosolic and mitochondrial energy substrate metabolism, while favoring leucine incorporation into protein synthesis rather than oxidation in the CAC. Improved understanding of factors governing these metabolic perturbations may serve as a basis for interventions and thereby improve success rate from weaning from ECMO. PMID:23959443

Kajimoto, Masaki; O'Kelly Priddy, Colleen M.; Ledee, Dolena R.; Xu, Chun; Isern, Nancy; Olson, Aaron K.; Rosiers, Christine Des; Portman, Michael A.

2013-01-01

274

Spray-dried porcine plasma reduces the effects of staphylococcal enterotoxin B on glucose transport in rat intestine.  

PubMed

We investigated the intestinal transport of D-glucose (D-Glc) and 3 essential amino acids in a model of intestinal inflammation, and the effects of dietary supplementation with animal plasma proteins on this function. Wistar Lewis rats were fed a diet containing an isonitrogenous amount of milk protein (control group) or a diet supplemented with either spray-dried animal plasma (SDAP) or immunoglobulin concentrate (IC) from porcine plasma, from d 21 of life (weaning) until d 35. On d 30 and 33, rats were challenged intraperitoneally with Staphylococcus aureus enterotoxin B (SEB; groups SEB, SEB-SDAP, and SEB-IC) and on d 35, brush border membrane vesicles (BBMVs) were prepared and used for transport and binding studies. Administration of SEB reduced D-Glc transport across sodium glucose transporter 1 [SGLT1; 20% reduction in maximal transport rate (Vmax); P < 0.05], without affecting the Michaelis constant (Km). The results from specific phlorizin binding, Western blot, and immunohistochemistry supported the view that the effects of SEB are due to reduced expression of D-Glc transporters in the apical membrane. SEB increased the passive diffusion constant (Kd) for D-Glc 3-fold (P < 0.05). SEB did not affect mediated or passive amino acid fluxes of L-leucine, L-methionine, or L-lysine. Dietary SDAP increased the D-Glc Vmax in the SEB group without affecting the passive component. Changes in d-Glc Vmax due to SEB and to the dietary treatments were correlated with changes in the number of SGLT1 transporters present in the BBMVs (r = 0.9468; P < 0.05). Dietary IC had no observed effect. We estimate that, in rats challenged with SEB, SDAP supplementation can increase glucose absorption by 8-9% during the interdigestive periods. PMID:15987845

Garriga, Carles; Pérez-Bosque, Anna; Amat, Concepció; Campbell, Joy M; Russell, Louis; Polo, Javier; Planas, Joana M; Moretó, Miquel

2005-07-01

275

Effects of single-walled carbon nanotubes on soil microorganisms  

NASA Astrophysics Data System (ADS)

Single-walled carbon nanotubes (SWCNTs) are novel materials that have the potential to be used in various commercial fields due to their unique physicochemical properties. As a result of commercial development of nanotechnology, SWCNTs may be discharged to the soil environment with unknown consequences. However, there are as yet no data in the scientific literature that demonstrate the effects of SWCNTs on microbial function in soils. Therefore, we aimed to determine the effects of SWCNTs on soil microbial activity through a 2-week incubation study on urban soils supplemented with different concentrations of SWCNTs ranging from 0 to 1000 ?g CNT/g soil. Fluorometric test using fluorogenic substrates were employed for the measurement of several enzyme activities in soil samples. More specifically, we determined the changes in the activities of cellobiohydrolase, ?-1,4-glucosidase, ?-1,4-xylosidase, ?-1,4-N-acetylglucosaminidase, L-leucine aminopeptidase and acid phosphatase which play important roles in the carbon, nitrogen, and phosphorus cycles in response to the addition of SWCNTs. We found that microbial enzyme activities decreased as the concentrations of SWCNT added increased. The lowest enzyme activities were observed under 1000 ?g CNT/g soil. The overall pattern shows that enzyme activities decreased slightly in the first 2-3 days and increased in the later stage of the incubation. Our results suggest that relatively high concentrations of SWCNTs can inhibit microbial activities, and this may be due to microbial cell membrane damage caused by SWCNTs. However, further study needs to be conducted to determine the mechanism responsible for inhibitory effect of SWCNTs on soil microbial activity. It can be concluded that changes in the activities of extracellular enzymes can indicate the effect of SWCNTs on soil microorganisms and nutrient cycling.

Jin, L.; Chung, H.; Son, Y.

2011-12-01

276

Development and evaluation of a dry powder formulation of liposome-encapsulated oseltamivir phosphate for inhalation.  

PubMed

Abstract This study aims to develop oseltamivir phosphate (OP) liposomes as inhalation powders by spray-drying based on the single factor investigation, which was mainly composed of lactose, l-leucine and mannitol. It was found that the ratio of OP and liposomes (1:10), inlet temperature (110?°C) and airflow rate (2.3?mL/min) showed optimized physical properties of OP liposomes. Deposition was evaluated after the aerosolization of powders at 600?L/h via the Aerolizer® into a twin-stage impinger. The concentrations of OP and oseltamivir carboxylate (OSCA) in rats plasma using LC-MS have been determined and performed via pharmacokinetic software DAS 2.0 package. The liposomal OP dry powders displayed an average particle size around 3.5?µm with fine particle fraction (FPF?=?35.40%). In vitro evaluation demonstrated a sustained release pattern accounting for 20% drug release compared to that of OP solution up to 90% drug release in 2?h. And the cumulative release percentage was up to 50% in 20?h. Atrioventricular fitting results indicated that all preparations were best fitted with a two-compartment model. There was a significant difference in MRT, Cmax and Tmax (p?

Tang, Yue; Zhang, Heyang; Lu, Xifeng; Jiang, Liqun; Xi, Xinyuan; Liu, Jianping; Zhu, Jiabi

2013-12-01

277

Regulation of Bud Rest in Tubers of Potato, Solanum tuberosum L  

PubMed Central

The rest period of the potato tuber was studied in relation to certain biochemical changes that are induced by gibberellic acid (GA3). The concentration of reducing sugars in excised plugs with buds treated with 10?4m GA3 decreased in the first 4 hours after treatment and then rapidly increased up to 70 hours. The pattern in control buds was similar, but the changes occurred more slowly. The response to GA3 is temperature-dependent and is not limited to any particular tissue of the tuber. The concentration of reducing sugars in excised buds increased proportionally to the log of the concentration of GA3 in a range from 10?8 to 10?4m. At 10?3m, GA3 slightly inhibited production of reducing sugars. Malonate inhibits the initial decrease and the subsequent increase in reducing sugars in control buds, but not the increase induced by GA3. Total protein in buds was not influenced by 10?4m GA3 over a period of 40 hours, nor did activity of ?-amylase increase significantly until 20 hours after beginning of treatment. Invertase activity was present initially and, in the presence of GA3, increased after 20 hours. GA3 had no effect on starch phosphorylase activity, which was always present and remained steady over the 20-hour test period. In short term experiments the rate of protein synthesis and synthesis of specific protein fractions were not affected by 10?4m GA3, as measured by the incorporation of l-phenylalanine-U-14C or by experiments with 14C- and 3H- labeled l-phenylalanine or l-leucine. PMID:16657283

Clegg, M. D.; Rappaport, Lawrence

1970-01-01

278

Solid-state NMR studies of aminocarboxylic salt bridges in L-lysine modified cellulose.  

PubMed

LysCel is a cellulose-based material in which l-lysine molecules are grafted with their amino side chains to the cellulose hydroxyl groups. This modification increases considerably the mechanical strength and resistance of cellulosic structures toward water. It has been attributed to the formation of double salt bridges between lysine aminocarboxyl groups in the zwitterionic state. In order to characterize this unusual structure, we have performed high-resolution solid-state (15)N and (13)C CPMAS NMR experiments on LysCel samples labeled with (15)N in the alpha-position or epsilon-position. Furthermore, (13)C-(15)N REDOR experiments were performed on LysCel where half of the aminocarboxyl groups were labeled in 1-position with 13C and the other half in alpha-position with (15)N. The comparison with the 13C and 15N chemical shifts of l-leucine lyophilized at different pH shows that the aminocarboxyl groups of LysCel are indeed zwitterionic. The REDOR experiments indicate distances of about 3.5 A between the carboxyl carbon and the nitrogen atoms of different aminocarboxyl groups, indicating that the latter are in close contact with each other. However, the data are not compatible with isolated aminocarboxyl dimers but indicate the assembly of zwitterionic aminocarboxyl dimers either in a flat ribbon or as tetramers, exhibiting similar intra- and interdimer (13)C...(15)N distances. This interaction of several aminocarboxyl groups is responsible for the zwitterionic state, in contrast to the gas phase, where amino acid dimers exhibiting two OHN hydrogen bonds are neutral. PMID:19117475

Manríquez, Ricardo; López-Dellamary, Fernando A; Frydel, Jaroslaw; Emmler, Thomas; Breitzke, Hergen; Buntkowsky, Gerd; Limbach, Hans-Heinrich; Shenderovich, Ilja G

2009-01-29

279

Defects of protein production in erythroid cells revealed in a zebrafish Diamond–Blackfan anemia model for mutation in RPS19  

PubMed Central

Diamond–Blackfan anemia (DBA) is a rare congenital red cell aplasia that classically presents during early infancy in DBA patients. Approximately, 25% of patients carry a mutation in the ribosomal protein (RP) S19 gene; mutations in RPS24, RPS17, RPL35A, RPL11, and RPL5 have been reported. How ribosome protein deficiency causes defects specifically to red blood cells in DBA has not been well elucidated. To genetically model the predominant ribosome defect in DBA, we generated an rps19 null mutant through the use of TALEN-mediated gene targeting in zebrafish. Molecular characterization of this mutant line demonstrated that rps19 deficiency reproduced the erythroid defects of DBA, including a lack of mature red blood cells and p53 activation. Notably, we found that rps19 mutants' production of globin proteins was significantly inhibited; however, globin transcript level was either increased or unaffected in rps19 mutant embryos. This dissociation of RNA/protein levels of globin genes was confirmed in another zebrafish DBA model with defects in rpl11. Using transgenic zebrafish with specific expression of mCherry in erythroid cells, we showed that protein production in erythroid cells was decreased when either rps19 or rpl11 was mutated. L-Leucine treatment alleviated the defects of protein production in erythroid cells and partially rescued the anemic phenotype in both rps19 and rpl11 mutants. Analysis of this model suggests that the decreased protein production in erythroid cells likely contributes to the blood-specific phenotype of DBA. Furthermore, the newly generated rps19 zebrafish mutant should serve as a useful animal model to study DBA. Our in vivo findings may provide clues for the future therapy strategy for DBA. PMID:25058426

Zhang, Y; Ear, J; Yang, Z; Morimoto, K; Zhang, B; Lin, S

2014-01-01

280

Effects of Leucine Supplementation and Serum Withdrawal on Branched-Chain Amino Acid Pathway Gene and Protein Expression in Mouse Adipocytes  

PubMed Central

The essential branched-chain amino acids (BCAA), leucine, valine and isoleucine, are traditionally associated with skeletal muscle growth and maintenance, energy production, and generation of neurotransmitter and gluconeogenic precursors. Recent evidence from human and animal model studies has established an additional link between BCAA levels and obesity. However, details of the mechanism of regulation of BCAA metabolism during adipogenesis are largely unknown. We interrogated whether the expression of genes and proteins involved in BCAA metabolism are sensitive to the adipocyte differentiation process, and responsive to nutrient stress from starvation or BCAA excess. Murine 3T3-L1 preadipocytes were differentiated to adipocytes under control conditions and under conditions of L-leucine supplementation or serum withdrawal. RNA and proteins were isolated at days 0, 4 and 10 of differentiation to represent pre-differentiation, early differentiation and late differentiation stages. Expression of 16 BCAA metabolism genes was quantified by quantitative real-time PCR. Expression of the protein levels of branched-chain amino acid transaminase 2 (Bcat2) and branched-chain alpha keto acid dehydrogenase (Bckdha) was quantified by immunoblotting. Under control conditions, all genes displayed induction of gene expression during early adipogenesis (Day 4) compared to Day 0. Leucine supplementation resulted in an induction of Bcat2 and Bckdha genes during early and late differentiation. Western blot analysis demonstrated condition-specific concordance between gene and protein expression. Serum withdrawal resulted in undetectable Bcat2 and Bckdha protein levels at all timepoints. These results demonstrate that the expression of genes related to BCAA metabolism are regulated during adipocyte differentiation and influenced by nutrient levels. These results provide additional insights on how BCAA metabolism is associated with adipose tissue function and extends our understanding of the transcriptomic response of this pathway to variations in nutrient availability. PMID:25050624

Vivar, Juan C.; Knight, Megan S.; Pointer, Mildred A.; Gwathmey, Judith K.; Ghosh, Sujoy

2014-01-01

281

The contribution of phenylalanine to tyrosine metabolism in vivo. Studies in the post-absorptive and phenylalanine-loaded rat.  

PubMed

1. Rates of appearance and oxidation of plasma L-leucine, L-phenylalanine and L-tyrosine, as well as conversion of plasma phenylalanine into plasma tyrosine, were determined in 90-120 g rats after overnight starvation and while receiving 115-120 mumol of L-phenylalanine/h. 2. In the post-absorptive state, plasma tyrosine and phenylalanine appearances were similar, despite the fact that 22% of plasma tyrosine appearance could be attributed to the hydroxylation of phenylalanine. 3. A constant infusion of 115-120 mumol of L-phenylalanine/h did not significantly alter plasma leucine kinetics, but increased appearance of plasma phenylalanine and tyrosine. The percentage of phenylalanine and tyrosine appearance that was oxidized increased from 12.1% and 24.4% to 37.3% and 48.0% respectively. In phenylalanine-loaded rats, 72% of plasma tyrosine appearance could be attributed to the conversion of phenylalanine. 4. Whole-body tyrosine oxidation measured from a continuous infusion of either L-[14C]tyrosine or L-[14C]phenylalanine differed by 165%. 5. It can be concluded that, in the post-absorptive state, phenylalanine hydroxylation makes a substantial contribution to the plasma appearance of tyrosine and is significantly increased when phenylalanine is administered. The disposal of excess infused phenylalanine is a result of a greater percentage of plasma phenylalanine being converted into tyrosine and a greater proportion of tyrosine being further oxidized. However, apparent tyrosine oxidation rates estimated from plasma tyrosine specific radioactivities and appearance of expired 14CO2 during administration of [14C]tyrosine are underestimates of true rates, in part because tyrosine generated from phenylalanine hydroxylation is catabolized without freely equilibrating with the plasma compartment. PMID:6870807

Moldawer, L L; Kawamura, I; Bistrian, B R; Blackburn, G L

1983-03-15

282

Formation of Isobutene from 3-Hydroxy-3-Methylbutyrate by Diphosphomevalonate Decarboxylase?  

PubMed Central

Isobutene is an important commercial chemical used for the synthesis of butyl rubber, terephthalic acid, specialty chemicals, and a gasoline performance additive known as alkylate. Currently, isobutene is produced from petroleum and hence is nonrenewable. Here, we report that the Saccharomyces cerevisiae mevalonate diphosphate decarboxylase (ScMDD) can convert 3-hydroxy-3-methylbutyrate (3-HMB) to isobutene. Whole cells of Escherichia coli producing ScMDD with an N-terminal 6×His tag (His6-ScMDD) formed isobutene from 3-HMB at a rate of 154 pmol h?1 g cells?1. In contrast, no isobutene was detected from control cells lacking ScMDD. His6-ScMDD was purified by nickel affinity chromatography and shown to produce isobutene from 3-HMB at a rate of 1.33 pmol min?1 mg?1 protein. Controls showed that both His6-ScMDD and 3-HMB were required for detectable isobutene formation. Isobutene was identified by gas chromatography (GC) with flame ionization detection as well as by GC-mass spectrometry (MS). ScMDD was subjected to error-prone PCR, and two improved variants were characterized, ScMDD1 (I145F) and ScMDD2 (R74H). Whole cells of E. coli producing ScMDD1 and ScMDD2 produced isobutene from 3-HMB at rates of 3,000 and 5,888 pmol h?1 g cells?1, which are 19- and 38-fold increases compared to rates for cells producing His6-ScMDD. This showed that genetic modifications can be used to increase the rate at which ScMDD converts 3-HMB to isobutene. Because 3-HMB can be produced from l-leucine, ScMDD has a potential application for the production of renewable isobutene. Moreover, isobutene is a gas, which might simplify its purification from a fermentation medium, substantially reducing production costs. PMID:20971863

Gogerty, David S.; Bobik, Thomas A.

2010-01-01

283

Cu(II)-dipeptide complexes of 2-(4'-thiazolyl)benzimidazole: Synthesis, DNA oxidative damage, antioxidant and in vitro antitumor activity.  

PubMed

Two new Cu(II)-dipeptide complexes of 2-(4'-thiazolyl)benzimidazole, [Cu(Gly-Gly)(TBZ)(Cl)]·4H2O (1) and [Cu(Gly-l-Leu)(TBZ)(Cl)]·H2O (2) (Gly-Gly=glycyl-glycine anion, Gly-l-Leu=glycyl-l-leucine anion and TBZ=2-(4'-thiazolyl)benzimidazole) have been synthesized and characterized by elemental analyses, molar conductance measurements and spectroscopy methods (IR, UV-visible, electrospray ionization mass spectra (ESI-MS) and EPR). The DNA binding and cleavage properties of the complexes monitored by multi-spectroscopic techniques (UV absorption, fluorescence and circular dichroism), viscosity determination and agarose gel electrophoresis indicated that the complexes bound to calf thymus (CT)-DNA via a partial intercalative mode with considerable intrinsic binding constants (Kb=1.64×10(5)M(-1) for 1 and 2.59×10(5)M(-1) for 2), and cleaved pBR322 DNA efficiently in the mediation of ascorbic acid (AA), probably via an oxidative damage mechanism induced by OH. The antioxidant activities of the complexes have been evaluated by means of modified nitroblue tetrazolium (NBT) photoreduction and cellular antioxidant activity (CAA) assays using HepG2 cells as a model, and it was found that IC50 values of 1 and 2 for dismutation of O2(-) were 0.172 and 0.247?M, respectively, and the CAA50 values were 10.57 and 10.74?M. In addition, the complexes were subjected to in vitro cytotoxicity against three human carcinoma cell lines (HeLa, A549 and HepG2), which revealed that the complexes exhibited effective cytotoxicity (IC50 values varying from 33.17 to 100?M) and selective inhibition toward HeLa cell lines. These findings indicate that the complexes have the potential to act as effective metallopeptide chemotherapeutic agents. PMID:25528481

Fu, Xia-Bing; Zhang, Jia-Jia; Liu, Dan-Dan; Gan, Qian; Gao, Hong-Wei; Mao, Zong-Wan; Le, Xue-Yi

2015-02-01

284

Improved narrowband dipolar recoupling for homonuclear distance measurements in rotating solids.  

PubMed

Recovery of the magnetic dipolar interaction between nuclei bearing the same gyromagnetic ratio in rotating solids can be promoted by synchronous rf irradiation. Determination of the dipolar interaction strength can serve as a tool for structural elucidation in polycrystalline powders. Spinning frequency dependent narrow-band (nb) RFDR and SEDRA experiments are utilized as simple techniques for the determination of dipolar interactions between the nuclei in coupled homonuclear spin pairs. The magnetization exchange and coherence dephasing due to a fixed number of rotor-synchronously applied pi-pulses is monitored at spinning frequencies in the vicinity of the rotational resonance (R(2)) conditions. The powder nbRFDR and nbSEDRA decay curves of spin magnetizations and coherences, respectively, as a function of the spinning frequency can be measured and analyzed using simple rate equations providing a quantitative measure of the dipolar coupling. The effects of the phenomenological relaxation parameters in these rate equations are discussed and an improved methodology is suggested for analyzing nbRFDR data for small dipolar couplings. The distance between the labeled nuclei in the 1,3-(13)C(2)-hydroxybutyric acid molecule is rederived using existing nbRFDR results and the new simulation procedure. A nbSEDRA experiment has been performed successfully on a powder sample of singly labeled 1-(13)C-L-leucine measuring the dipolar interaction between the labeled carboxyl carbon and the natural abundant beta-carbon. Both narrowband techniques are employed for the determination of the nuclear distances between the side-chain carbons of leucine and its carbonyl carbon in a tripeptide Leu-Gly-Phe that is singly (13)C-labeled at the leucine carbonyl carbon position. PMID:11846581

Goobes, G; Vega, S

2002-02-01

285

Cyanobacterial toxins: removal during drinking water treatment, and human risk assessment.  

PubMed Central

Cyanobacteria (blue-green algae) produce toxins that may present a hazard for drinking water safety. These toxins (microcystins, nodularins, saxitoxins, anatoxin-a, anatoxin-a(s), cylindrospermopsin) are structurally diverse and their effects range from liver damage, including liver cancer, to neurotoxicity. The occurrence of cyanobacteria and their toxins in water bodies used for the production of drinking water poses a technical challenge for water utility managers. With respect to their removal in water treatment procedures, of the more than 60 microcystin congeners, microcystin-LR (L, L-leucine; R, L-arginine) is the best studied cyanobacterial toxin, whereas information for the other toxins is largely lacking. In response to the growing concern about nonlethal acute and chronic effects of microcystins, the World Health Organization has recently set a new provisional guideline value for microcystin-LR of 1.0 microg/L drinking water. This will lead to further efforts by water suppliers to develop effective treatment procedures to remove these toxins. Of the water treatment procedures discussed in this review, chlorination, possibly micro-/ultrafiltration, but especially ozonation are the most effective in destroying cyanobacteria and in removing microcystins. However, these treatments may not be sufficient during bloom situations or when a high organic load is present, and toxin levels should therefore be monitored during the water treatment process. In order to perform an adequate human risk assessment of microcystin exposure via drinking water, the issue of water treatment byproducts will have to be addressed in the future. PMID:10698727

Hitzfeld, B C; Höger, S J; Dietrich, D R

2000-01-01

286

Downregulation of LAT1 expression suppresses cholangiocarcinoma cell invasion and migration.  

PubMed

Currently, there is no effective treatment for cholangiocarcinoma (CCA), which is the most prevalent in the northeastern part of Thailand. A new molecular target for the treatment of CCA is, therefore, urgently needed. Although L-type amino acid transporter 1 (LAT1) is highly expressed in CCA cells, its role in malignant phenotypes of CCA cells remains unclear. This study aimed to investigate the impact of LAT1 on proliferation, migration, and invasion of KKU-M213 cells, the CCA cells derived from Thai patients with intrahepatic cholangiocarcinoma. Results showed that KKU-M213 cells expressed all LAT isoforms (LAT1, LAT2, LAT3 and LAT4). The expressions of LAT1 and its associated protein 4F2hc were highest whereas those of LAT2 and LAT4 were extremely low. Treatment with 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH) reduced L-leucine uptake concomitant with an inhibition of cell motility and, to a lesser extent, on cell proliferation. It also induced a time dependent up-regulation of LAT1 and 4F2hc expressions. Similarly, cell migration and invasion, but not proliferation, were reduced in LAT1 knockdown KKU-M213 cells. In addition, silencing of LAT1 inhibited the expressions of 4F2hc mRNA and protein whereas the expression of microRNA-7, the 4F2hc down-regulator, was increased. Furthermore, the phosphorylation levels of ERK1/2 and p70S6K were reduced after LAT1 knockdown. Collectively, these results suggest that suppression of cell invasion and migration in LAT1 knockdown KKU-M213 cells may be partly mediated through the inhibition of the 4F2hc-signaling pathway by the up-regulation of microRNA-7. Based on this finding, LAT1 may be a potential therapeutic target for treating CCA. PMID:24726839

Janpipatkul, Keatdamrong; Suksen, Kanoknetr; Borwornpinyo, Suparerk; Jearawiriyapaisarn, Natee; Hongeng, Suradej; Piyachaturawat, Pawinee; Chairoungdua, Arthit

2014-08-01

287

Discovery of new angiotensin converting enzyme (ACE) inhibitors from medicinal plants to treat hypertension using an in vitro assay  

PubMed Central

Background and purpose of the study Angiotensin converting enzyme (ACE) inhibitors plays a critical role in treating hypertension. The purpose of the present investigation was to evaluate ACE inhibition activity of 50 Iranian medicinal plants using an in vitro assay. Methods The ACE activity was evaluated by determining the hydrolysis rate of substrate, hippuryl-L-histidyl-L-leucine (HHL), using reverse phase high performance liquid chromatography (RP-HPLC). Total phenolic content and antioxidant activity were determined by Folin-Ciocalteu colorimetric method and DPPH radical scavenging assay respectively. Results Six extracts revealed?>?50% ACE inhibition activity at 330 ?g/ml concentration. They were Berberis integerrima Bunge. (Berberidaceae) (88.2?±?1.7%), Crataegus microphylla C. Koch (Rosaceae) (80.9?±?1.3%), Nymphaea alba L. (Nymphaeaceae) (66.3?±?1.2%), Onopordon acanthium L. (Asteraceae) (80.2?±?2.0%), Quercus infectoria G. Olivier. (Fagaceae) (93.9?±?2.5%) and Rubus sp. (Rosaceae) (51.3?±?1.0%). Q. infectoria possessed the highest total phenolic content with 7410?±?101 mg gallic acid/100 g dry plant. Antioxidant activity of Q. infectoria (IC50 value 1.7?±?0.03 ?g/ml) was more than that of BHT (IC50 value of 10.3?±?0.15 ?g/ml) and Trolox (IC50 value of 3.2?±?0.06 ?g/ml) as the positive controls. Conclusions In this study, we introduced six medicinal plants with ACE inhibition activity. Despite the high ACE inhibition and antioxidant activity of Q. infectoria, due to its tannin content (tannins interfere in ACE activity), another plant, O. acanthium, which also had high ACE inhibition and antioxidant activity, but contained no tannin, could be utilized in further studies for isolation of active compounds. PMID:24359711

2013-01-01

288

Simultaneous chiral separation and determination of ephedrine alkaloids by MEKC-ESI-MS using polymeric surfactant I: method development.  

PubMed

In this work, simultaneous separation of eight stereoisomers of ephedrine and related compounds ((+/-)-ephedrine, (+/-)-pseudoephedrine, (+/-)-norephedrine and (+/-)-N-methylephedrine) was accomplished using a polymeric chiral surfactant, i.e. polysodium N-undecenoxycarbonyl-L-leucinate (poly-L-SUCL) by chiral (C)MEKC-ESI-MS. The conditions of CMEKC were first investigated. The baseline separation of all eight stereoisomers of ephedrine and related compounds was achieved under optimum CMEKC conditions (35 mM poly-L-SUCL, 15 mM NH(4)OAc, pH 6.0, 30% v/v ACN, 30 kV and 20 degrees C) in less than 30 min. Next, a central composite design for response surface modeling has been described to evaluate the electrospray chamber parameters and the sheath liquid conditions. Optimum mass abundance of stereoisomers of ephedrine and related compounds was observed using the spray chamber parameters, namely 250 degrees C drying gas temperature and 8 L/min drying gas flow rate at a nebulizer pressure of 4 psi. Furthermore, the experimental design indicates that the optimum mass abundance of the stereoisomers of ephedrine and related compounds can be obtained using a sheath liquid containing 80:20 v/v methanol-water, 5 mM NH(4)OAc at pH 8.5 delivered at 5 microL/min. Finally, compared to MEKC-UV, the use of poly-L-SUCL in MEKC-MS provided significantly higher sensitivity for stereoisomers of ephedrine and related compounds. PMID:17465416

Hou, Jingguo; Zheng, Jie; Rizvi, Syed A A; Shamsi, Shahab A

2007-05-01

289

The effect of eicosapentaenoic and docosahexaenoic acid on protein synthesis and breakdown in murine C2C12 myotubes  

SciTech Connect

Highlights: ? EPA can enhance protein synthesis and retard protein breakdown in muscle cells. ? These effects were concurrent with increases in p70s6k and FOXO3a phosphorylation. ? EPA may be a useful tool in the treatment of muscle wasting conditions. -- Abstract: Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been found to stimulate protein synthesis with little information regarding their effects on protein breakdown. Furthermore whether there are distinct effects of EPA and DHA remains to be established. The aim of the current study was to determine the distinct effects of EPA and DHA on protein synthesis, protein breakdown and signalling pathways in C2C12 myotubes. Fully differentiated C2C12 cells were incubated for 24 h with 0.1% ethanol (control), 50 ?M EPA or 50 ?M DHA prior to experimentation. After serum (4 h) and amino acid (1 h) starvation cells were stimulated with 2 mM L-leucine and protein synthesis measured using {sup 3}H-labelled phenylalanine. Protein breakdown was measured using {sup 3}H-labelled phenylalanine and signalling pathways (Akt, mTOR, p70S6k, 4EBP1, rps6 and FOXO3a) via Western blots. Data revealed that after incubation with EPA protein synthesis was 25% greater (P < 0.05) compared to control cells, with no effect of DHA. Protein breakdown was 22% (P < 0.05) lower, compared to control cells, after incubation with EPA, with no effect of DHA. Analysis of signalling pathways revealed that both EPA and DHA incubation increased (P < 0.05) p70s6k phosphorylation, EPA increased (P < 0.05) FOXO3a phosphorylation, with no alteration in other signalling proteins. The current study has demonstrated distinct effects of EPA and DHA on protein metabolism with EPA showing a greater ability to result in skeletal muscle protein accretion.

Kamolrat, Torkamol [Musculoskeletal Research Programme, Institute of Medical Sciences, University of Aberdeen, AB25 2ZD (United Kingdom)] [Musculoskeletal Research Programme, Institute of Medical Sciences, University of Aberdeen, AB25 2ZD (United Kingdom); Gray, Stuart R., E-mail: s.r.gray@abdn.ac.uk [Musculoskeletal Research Programme, Institute of Medical Sciences, University of Aberdeen, AB25 2ZD (United Kingdom)

2013-03-22

290

Evaluation and Modification of Commercial Dry Powder Inhalers for the Aerosolization of a Submicrometer Excipient Enhanced Growth (EEG) Formulation  

PubMed Central

The aim of this study was to evaluate and modify commercial dry powder inhalers (DPIs) for the aerosolization of a submicrometer excipient enhanced growth (EEG) formulation. The optimized device and formulation combination was then tested in a realistic in vitro mouth-throat - tracheobronchial (MT-TB) model. An optimized EEG submicrometer powder formulation, consisting of albuterol sulfate (drug), mannitol (hygroscopic excipient), L-leucine (dispersion enhancer) and poloxamer 188 (surfactant) in a ratio of 30:48:20:2 was prepared using a Büchi Nano spray dryer. The aerosolization performance of the EEG formulation was evaluated with 5 conventional DPIs: Aerolizer, Novolizer, HandiHaler, Exubera and Spiros. To improve powder dispersion, the HandiHaler was modified with novel mouth piece (MP) designs. The aerosol performance of each device was assessed using a next generation impactor (NGI) at airflow rates generating a pressure drop of 4 kPa across the DPI. In silico and in vitro deposition and hygroscopic growth of formulations was studied using a MT-TB airway geometry model. Both Handihaler and Aerolizer produced high emitted doses (ED) together with a significant submicrometer aerosol fraction. A modified HandiHaler with a MP including a three-dimensional (3D) array of rods (HH-3D) produced a submicrometer particle fraction of 38.8% with a conventional fine particle fraction (% <5µm) of 97.3%. The mass median diameter (MMD) of the aerosol was reduced below 1 µm using this HH-3D DPI. The aerosol generated from the modified HandiHaler increased to micrometer size (2.8 µm) suitable for pulmonary deposition, when exposed to simulated respiratory conditions, with negligible mouth-throat (MT) deposition (2.6 %). PMID:23608613

Son, Yoen-Ju; Longest, P. Worth; Tian, Geng; Hindle, Michael

2013-01-01

291

The molecular mechanism of intestinal levodopa absorption and its possible implications for the treatment of Parkinson's disease.  

PubMed

Levodopa (L-DOPA) is the naturally occurring precursor amino acid for dopamine and the main therapeutic agent for neurologic disorders due to dopamine depletion, such as Parkinson's disease. l-DOPA absorption in small intestine has been suggested to be mediated by the large neutral amino acids transport machinery, but the identity of the involved transporters is unknown. Clinically, coadministration of l-DOPA and dietary amino acids is avoided to decrease competition for transport in intestine and at the blood-brain barrier. l-DOPA is routinely coadministered with levodopa metabolism inhibitors (dopa-decarboxylase and cathechol-O-methyl transferase inhibitors) that share structural similarity with levodopa. In this systematic study involving Xenopus laevis oocytes and Madin-Darby canine kidney epithelia expression systems and ex vivo preparations from wild-type and knockout mice, we identified the neutral and dibasic amino acids exchanger (antiporter) b(0,+)AT-rBAT (SLC7A9-SLC3A1) as the luminal intestinal l-DOPA transporter. The major luminal cotransporter (symporter) B(0)AT1 (SLC6A19) was not involved in levodopa transport. L-Leucine and L-arginine competed with levodopa across the luminal enterocyte membrane as expected for b(0,+)AT-rBAT substrates, whereas dopa-decarboxylase and cathechol-O-methyl transferase inhibitors had no effect. The presence of amino acids in the basolateral compartment mimicking the postprandial phase increased transepithelial levodopa transport by stimulating basolateral efflux via the antiporter LAT2-4F2 (SLC7A8-SLC3A2). Additionally, the aromatic amino acid uniporter TAT1 (SLC16A10) was shown to play a major role in l-DOPA efflux from intestinal enterocytes. These results identify the molecular mechanisms mediating small intestinal levodopa absorption and suggest strategies for optimization of delivery and absorption of this important prodrug. PMID:25073474

Camargo, Simone M R; Vuille-dit-Bille, Raphael N; Mariotta, Luca; Ramadan, Tamara; Huggel, Katja; Singer, Dustin; Götze, Oliver; Verrey, François

2014-10-01

292

Abrin Immunotoxin: Targeted Cytotoxicity and Intracellular Trafficking Pathway  

PubMed Central

Background Immunotherapy is fast emerging as one of the leading modes of treatment of cancer, in combination with chemotherapy and radiation. Use of immunotoxins, proteins bearing a cell-surface receptor-specific antibody conjugated to a toxin, enhances the efficacy of cancer treatment. The toxin Abrin, isolated from the Abrus precatorius plant, is a type II ribosome inactivating protein, has a catalytic efficiency higher than any other toxin belonging to this class of proteins but has not been exploited much for use in targeted therapy. Methods Protein synthesis assay using 3[H] L-leucine incorporation; construction and purification of immunotoxin; study of cell death using flow cytometry; confocal scanning microscopy and sub-cellular fractionation with immunoblot analysis of localization of proteins. Results We used the recombinant A chain of abrin to conjugate to antibodies raised against the human gonadotropin releasing hormone receptor. The conjugate inhibited protein synthesis and also induced cell death specifically in cells expressing the receptor. The conjugate exhibited differences in the kinetics of inhibition of protein synthesis, in comparison to abrin, and this was attributed to differences in internalization and trafficking of the conjugate within the cells. Moreover, observations of sequestration of the A chain into the nucleus of cells treated with abrin but not in cells treated with the conjugate reveal a novel pathway for the movement of the conjugate in the cells. Conclusions This is one of the first reports on nuclear localization of abrin, a type II RIP. The immunotoxin mAb F1G4-rABRa-A, generated in our laboratory, inhibits protein synthesis specifically on cells expressing the gonadotropin releasing hormone receptor and the pathway of internalization of the protein is distinct from that seen for abrin. PMID:23472175

Gadadhar, Sudarshan; Karande, Anjali A.

2013-01-01

293

Cyanobacterial toxins: removal during drinking water treatment, and human risk assessment.  

PubMed

Cyanobacteria (blue-green algae) produce toxins that may present a hazard for drinking water safety. These toxins (microcystins, nodularins, saxitoxins, anatoxin-a, anatoxin-a(s), cylindrospermopsin) are structurally diverse and their effects range from liver damage, including liver cancer, to neurotoxicity. The occurrence of cyanobacteria and their toxins in water bodies used for the production of drinking water poses a technical challenge for water utility managers. With respect to their removal in water treatment procedures, of the more than 60 microcystin congeners, microcystin-LR (L, L-leucine; R, L-arginine) is the best studied cyanobacterial toxin, whereas information for the other toxins is largely lacking. In response to the growing concern about nonlethal acute and chronic effects of microcystins, the World Health Organization has recently set a new provisional guideline value for microcystin-LR of 1.0 microg/L drinking water. This will lead to further efforts by water suppliers to develop effective treatment procedures to remove these toxins. Of the water treatment procedures discussed in this review, chlorination, possibly micro-/ultrafiltration, but especially ozonation are the most effective in destroying cyanobacteria and in removing microcystins. However, these treatments may not be sufficient during bloom situations or when a high organic load is present, and toxin levels should therefore be monitored during the water treatment process. In order to perform an adequate human risk assessment of microcystin exposure via drinking water, the issue of water treatment byproducts will have to be addressed in the future. PMID:10698727

Hitzfeld, B C; Höger, S J; Dietrich, D R

2000-03-01

294

Nutritional profile of phytococktail from trans-Himalayan plants.  

PubMed

We estimated the nutritive value, vitamin content, amino acid composition, fatty acid content, and mineral profile of a phytococktail comprising sea buckthorn (Hippophae rhamnoides), apricot (Prunus armeniaca), and roseroot (Rhodiola imbricata) from trans-Himalaya. The free vitamin forms in the phytococktail were determined by rapid resolution liquid chromatography/tandem mass spectrometry (RRLC-MS/MS). Vitamin E and B-complex vitamins were detected as the principle vitamins. Reversed-phase high performance liquid chromatography (RP-HPLC) with pre-column derivatization was used for identification and quantification of amino acids. Eight essential and eleven non-essential amino acids were quantified, and the content ranged between 76.33 and 9485.67 µg/g. Among the essential amino acids, L-methionine, L-phenylalanine, L-lysine, L-leucine, and L-histidine were found to be the dominant contributors. We also quantified the fatty acids in the phytococktail by using gas chromatography coupled with a flame ionization detector (GC-FID) with fatty acid methyl esters (FAMEs) derivatization. The analysis revealed the presence of 4 major fatty acids contributing to the total lipid content. Palmitic acid was found to be the rich source of saturated fatty acid (SFA) and constituted ?31% of the total lipid content. Among the unsaturated fatty acids (UFAs), palmitoleic acid (43.47%), oleic acid (20.89%), and linoleic acid (4.31%) were prominent. The mineral profiling was carried out by inductively coupled plasma optical emission spectrometer (ICP-OES), and it was found to contain a number of important dietary mineral elements. The harsh climatic conditions, difficult terrain, and logistic constraints at high altitude regions of Indian trans-Himalayan cold desert lead to the scarcity of fresh fruits and vegetables. Therefore, the source of multiple vitamins, essential amino acids, fatty acids, and dietary minerals from the phytococktail would provide great health benefit in the stressful environment and could be used as a high value nutritional supplement. PMID:24376624

Dhar, Priyanka; Tayade, Amol B; Kumar, Jatinder; Chaurasia, Om P; Srivastava, Ravi B; Singh, Shashi B

2013-01-01

295

Luminal l-glutamate enhances duodenal mucosal defense mechanisms via multiple glutamate receptors in rats  

PubMed Central

Presence of taste receptor families in the gastrointestinal mucosa suggests a physiological basis for local and early detection of a meal. We hypothesized that luminal l-glutamate, which is the primary nutrient conferring fundamental umami or proteinaceous taste, influences mucosal defense mechanisms in rat duodenum. We perfused the duodenal mucosa of anesthetized rats with l-glutamate (0.1–10 mM). Intracellular pH (pHi) of the epithelial cells, blood flow, and mucus gel thickness (MGT) were simultaneously and continuously measured in vivo. Some rats were pretreated with indomethacin or capsaicin. Duodenal bicarbonate secretion (DBS) was measured with flow-through pH and CO2 electrodes. We tested the effects of agonists or antagonists for metabotropic glutamate receptor (mGluR) 1 or 4 or calcium-sensing receptor (CaSR) on defense factors. Luminal l-glutamate dose dependently increased pHi and MGT but had no effect on blood flow in the duodenum. l-glutamate (10 mM)-induced cellular alkalinization and mucus secretion were inhibited by pretreatment with indomethacin or capsaicin. l-glutamate effects on pHi and MGT were mimicked by mGluR4 agonists and inhibited by an mGluR4 antagonist. CaSR agonists acidified cells with increased MGT and DBS, unlike l-glutamate. Perfusion of l-glutamate with inosinate (inosine 5?-monophosphate, 0.1 mM) enhanced DBS only in combination, suggesting synergistic activation of the l-glutamate receptor, typical of taste receptor type 1. l-leucine or l-aspartate had similar effects on DBS without any effect on pHi and MGT. Preperfusion of l-glutamate prevented acid-induced cellular injury, suggesting that l-glutamate protects the mucosa by enhancing mucosal defenses. Luminal l-glutamate may activate multiple receptors and afferent nerves and locally enhance mucosal defenses to prevent subsequent injury attributable to acid exposure in the duodenum. PMID:19643955

Watanabe, Chikako; Mizumori, Misa; Kaunitz, Jonathan D.

2009-01-01

296

Engineering hydrophobically modified chitosan for enhancing the dispersion of respirable microparticles of levofloxacin.  

PubMed

The potential of amphiphilic chitosan formed by grafting octanoyl chains on the chitosan backbone for pulmonary delivery of levofloxacin has been studied. The success of polymer synthesis was confirmed using FT-IR and NMR, whilst antimicrobial activity was assessed against Pseudomonas aeruginosa. Highly dispersible dry powders for delivery as aerosols were prepared with different amounts of chitosan and octanoyl chitosan to study the effect of hydrophobic modification and varying concentration of polymer on aerosolization of drug. Powders were prepared by spray-drying from an aqueous solution containing levofloxacin and chitosan/amphiphilic octanoyl chitosan. l-leucine was also used to assess its effect on aerosolization. Following spray-drying, the resultant powders were characterized using scanning electron microscopy, laser diffraction, dynamic light scattering, HPLC, differential scanning calorimetry, thermogravimetric analysis and X-ray powder diffraction. The in vitro aerosolization profile was determined using a Next Generation Impactor, whilst in vitro antimicrobial assessment was performed using MIC assay. Microparticles of chitosan have the property of mucoadhesion leading to potential increased residence time in the pulmonary mucus, making it important to test the toxicity of these formulations. In-vitro cytotoxicity evaluation using MTT assay was performed on A549 cell line to determine the toxicity of formulations and hence feasibility of use. The MTT assay confirmed that the polymers and the formulations were non-cytotoxic. Hydrophobically modifying chitosan showed significantly lower MIC (4-fold) than the commercial chitosan against P. aeruginosa. The powders generated were of suitable aerodynamic size for inhalation having a mass median aerodynamic diameter less than 4.5?m for formulations containing octanoyl chitosan. These highly dispersible powders have minimal moisture adsorption and hence an emitted dose of more than 90% and a fine particle fraction (FPF) of 52%. Powders with non-modified chitosan showed lower dispersibility, with an emitted dose of 72% and FPF of 20%, as a result of high moisture adsorption onto the chitosan matrix leading to cohesiveness and subsequently decreased dispersibility. PMID:25305582

Merchant, Zahra; Taylor, Kevin M G; Stapleton, Paul; Razak, Sana A; Kunda, Nitesh; Alfagih, Iman; Sheikh, Khalid; Saleem, Imran Y; Somavarapu, Satyanarayana

2014-11-01

297

Nutritional Profile of Phytococktail from Trans-Himalayan Plants  

PubMed Central

We estimated the nutritive value, vitamin content, amino acid composition, fatty acid content, and mineral profile of a phytococktail comprising sea buckthorn (Hippophae rhamnoides), apricot (Prunus armeniaca), and roseroot (Rhodiola imbricata) from trans-Himalaya. The free vitamin forms in the phytococktail were determined by rapid resolution liquid chromatography/tandem mass spectrometry (RRLC-MS/MS). Vitamin E and B-complex vitamins were detected as the principle vitamins. Reversed-phase high performance liquid chromatography (RP-HPLC) with pre-column derivatization was used for identification and quantification of amino acids. Eight essential and eleven non-essential amino acids were quantified, and the content ranged between 76.33 and 9485.67 µg/g. Among the essential amino acids, L-methionine, L-phenylalanine, L-lysine, L-leucine, and L-histidine were found to be the dominant contributors. We also quantified the fatty acids in the phytococktail by using gas chromatography coupled with a flame ionization detector (GC-FID) with fatty acid methyl esters (FAMEs) derivatization. The analysis revealed the presence of 4 major fatty acids contributing to the total lipid content. Palmitic acid was found to be the rich source of saturated fatty acid (SFA) and constituted ?31% of the total lipid content. Among the unsaturated fatty acids (UFAs), palmitoleic acid (43.47%), oleic acid (20.89%), and linoleic acid (4.31%) were prominent. The mineral profiling was carried out by inductively coupled plasma optical emission spectrometer (ICP-OES), and it was found to contain a number of important dietary mineral elements. The harsh climatic conditions, difficult terrain, and logistic constraints at high altitude regions of Indian trans-Himalayan cold desert lead to the scarcity of fresh fruits and vegetables. Therefore, the source of multiple vitamins, essential amino acids, fatty acids, and dietary minerals from the phytococktail would provide great health benefit in the stressful environment and could be used as a high value nutritional supplement. PMID:24376624

Dhar, Priyanka; Tayade, Amol B.; Kumar, Jatinder; Chaurasia, Om P.; Srivastava, Ravi B.; Singh, Shashi B.

2013-01-01

298

Dual effect of DL-homocysteine and S-adenosylhomocysteine on brain synthesis of the glutamate receptor antagonist, kynurenic acid.  

PubMed

Increased serum level of homocysteine, a sulfur-containing amino acid, is considered a risk factor in vascular disorders and in dementias. The effect of homocysteine and metabolically related compounds on brain production of kynurenic acid (KYNA), an endogenous antagonist of glutamate ionotropic receptors, was studied. In rat cortical slices, DL-homocysteine enhanced (0.1-0.5 mM) or inhibited (concentration inducing 50% inhibition [IC50]=6.4 [5.5-7.5] mM) KYNA production. In vivo peripheral application of DL-homocysteine (1.3 mmol/kg intraperitoneally) increased KYNA content (pmol/g tissue) from 8.47 +/- 1.57 to 13.04 +/- 2.86 (P <0.01; 15 min) and 11.4 +/- 1.72 (P <0.01; 60 min) in cortex, and from 4.11 +/- 1.54 to 10.02 +/- 3.08 (P <0.01; 15 min) in rat hippocampus. High concentrations of DL-homocysteine (20 mM) applied via microdialysis probe decreased KYNA levels in rabbit hippocampus; this effect was antagonized partially by an antagonist of group I metabotropic glutamate receptors, LY367385. In vitro, S-adenosylhomocysteine acted similar to but more potently than DL-homocysteine, augmenting KYNA production at 0.03-0.08 mM and reducing it at > or =0.5 mM. The stimulatory effect of S-adenosylhomocysteine was abolished in the presence of the L-kynurenine uptake inhibitors L-leucine and L-phenyloalanine. Neither the N-methyl-D-aspartate (NMDA) antagonist CGS 19755 nor L-glycine influenced DL-homocysteine- and S-adenosylhomocysteine-induced changes of KYNA synthesis in vitro. DL-Homocysteine inhibited the activity of both KYNA biosynthetic enzymes, kynurenine aminotransferases (KATs) I and II, whereas S-adenosylhomocysteine reduced only the activity of KAT II. L-Methionine and L-cysteine, thiol-containing compounds metabolically related to homocysteine, acted only as weak inhibitors, reducing KYNA production in vitro and inhibiting the activity of KAT II (L-cysteine) or KAT I (L-methionine). The present data suggest that DL-homocysteine biphasically modulates KYNA synthesis. This seems to result from conversion of compound to S-adenosylhomocysteine, also acting dually on KYNA formation, and in part from the direct interaction of homocysteine with metabotropic glutamate receptors and KYNA biosynthetic enzymes. It seems probable that hyperhomocystemia-associated brain dysfunction is mediated partially by changes in brain KYNA level. PMID:15605380

Luchowska, E; Luchowski, P; Paczek, R; Ziembowicz, A; Kocki, T; Turski, W A; Wielosz, M; Lazarewicz, J; Urbanska, E M

2005-02-01

299

Effect of a Herbal-Leucine mix on the IL-1?-induced cartilage degradation and inflammatory gene expression in human chondrocytes  

PubMed Central

Background Conventional treatments for the articular diseases are often effective for symptom relief, but can also cause significant side effects and do not slow the progression of the disease. Several natural substances have been shown to be effective at relieving the symptoms of osteoarthritis (OA), and preliminary evidence suggests that some of these compounds may exert a favorable influence on the course of the disease. The objective of this study was to investigate the anti-inflammatory/chondroprotective potential of a Herbal and amino acid mixture containing extract of the Uncaria tomentosa, Boswellia spp., Lepidium meyenii and L-Leucine on the IL-1?-induced production of nitric oxide (NO), glycosaminoglycan (GAG), matrix metalloproteinases (MMPs), aggrecan (ACAN) and type II collagen (COL2A1) in human OA chondrocytes and OA cartilage explants. Methods Primary OA chondrocytes or OA cartilage explants were pretreated with Herbal-Leucine mixture (HLM, 1-10 ?g/ml) and then stimulated with IL-1? (5 ng/ml). Effect of HLM on IL-1?-induced gene expression of iNOS, MMP-9, MMP-13, ACAN and COL2A1 was verified by real time-PCR. Estimation of NO and GAG release in culture supernatant was done using commercially available kits. Results HLM tested in these in vitro studies was found to be an effective anti-inflammatory agent, as evidenced by strong inhibition of iNOS, MMP-9 and MMP-13 expression and NO production in IL-1?-stimulated OA chondrocytes (p < 0.05). Supporting these gene expression results, IL-1?-induced cartilage matrix breakdown, as evidenced by GAG release from cartilage explants, was also significantly blocked (p < 0.05). Moreover, in the presence of herbal-Leucine mixture (HLM) up-regulation of ACAN and COL2A1 expression in IL-1?-stimulated OA chondrocytes was also noted (p < 0.05). The inhibitory effects of HLM were mediated by inhibiting the activation of nuclear factor (NF)-kB in human OA chondrocytes in presence of IL-1?. Conclusion Our data suggests that HLM could be chondroprotective and anti-inflammatory agent in arthritis, switching chondrocyte gene expression from catabolic direction towards anabolic and regenerative, and consequently this approach may be potentially useful as a new adjunct therapeutic/preventive agent for OA or injury recovery. PMID:21854562

2011-01-01

300

The estimation of antistress properties of peat degradation products  

NASA Astrophysics Data System (ADS)

Introduction. It is known that polyphenol preparations, produced from peat, represent adaptogens, immunomodulators and can participate in regulation of genetic informational realization as triggers of nonspecific nature. These compounds promote launching of protein-synthesizing system that is very important under unfavorable influence on organism. The experimental data of last years confirmed doth therapeutic value of humic acids as adaptogenes and their antioxidant, anti-inflammatory, antimutogenic, radioprotective and other properties. Lysosomes take the key positions in many physiological and pathological processes of organism owing to their unique structural-functional properties, reactivity and plasticity. These organelles take especial meaning in increased functional activity under stress factors influence. In this way lysosomes become modulators of intracellular processes. It is known that under chronic stress, the systems of neurohumoral regulation and adaptation gradually run out, the function of brain cellular membrane structures disturbs. Understanding of stress developing mechanisms is necessary condition for means development of operative avoiding of the harmful consequences. Purpose. The aim of the work was to investigate corrective influence of hydrohumates on compartmentalization changing of lysosomal cysteine cathepsin H (EC 3.4.22.16) in different rat brain structures. The experiment was held on Wistar's rats (160-200 g weight) which were divided into 4 groups: 1 - the control group; 2 - the animals which were received the hydrohumate with water (10 mg hydrohumate (0,1% solution) per 1 kg of weight) during 3 weeks; 3 - the group of stressed rats (test "forced swimming" for 2 hours); 4 - the stressed rats which received the hydrohumate. The activity of lysosomal cysteine cathepsin H was determined spectrophotometerically by hydrolysis of 2-naphthyl-amid L-leucine (Koch-Light Lab., England). It was found out that intracellular compartmentalization changes of lysosomal cysteine protease (cathepsin H) occur as a result of increasing its free activity in 1,6 times in neocortex and 1,8 times in cerebellum, which testify to stress-induced disruption of architectonics and stability of brain cellular lysosomal membranes. These changes could be considered as important biochemical indicators of chronic stress severity. Besides, they could be interpreted as trigger switching over to another functional condition, when power of system reparation becomes not enough for effective removal of disorders. Conclusions. The hydrohumates make corrective action on activity indices of researched enzymes by decreasing it on 45%. Such influence testifies to its membranotrophic properties. It could be suggested that hydrohumates stimulate the reparative processes because of its high antioxidant activity and levels sharp fluctuation of physiological state.

Chorna, V. I.; Lyanna, O. L.

2009-04-01

301

A new treatment for human malignant melanoma targeting L-type amino acid transporter 1 (LAT1): A pilot study in a canine model  

SciTech Connect

Highlights: •LAT1 is highly expressed in tumors but at low levels in normal tissues. •We examine LAT1 expression and function in malignant melanoma (MM). •LAT1 expression in MM tissues and cell lines is higher than those in normal tissues. •LAT1 selective inhibitors inhibit amino acid uptake and cell growth in MM cells. •New chemotherapeutic protocols including LAT1 inhibitors are effective for treatment. -- Abstract: L-type amino acid transporter 1 (LAT1), an isoform of amino acid transport system L, transports branched or aromatic amino acids essential for fundamental cellular activities such as cellular growth, proliferation and maintenance. This amino acid transporter recently has received attention because of its preferential and up-regulated expression in a variety of human tumors in contrast to its limited distribution and low-level expression in normal tissues. In this study, we explored the feasibility of using LAT1 inhibitor as a new therapeutic agent for human malignant melanomas (MM) using canine spontaneous MM as a model for human MM. A comparative study of LAT expression was performed in 48 normal tissues, 25 MM tissues and five cell lines established from MM. The study observed LAT1 mRNA levels from MM tissues and cell lines that were significantly (P < 0.01) higher than in normal tissues. Additionally, MM with distant metastasis showed a higher expression than those without distant metastasis. Functional analysis of LAT1 was performed on one of the five cell lines, CMeC-1. [{sup 3}H]L-Leucine uptake and cellular growth activities in CMeC-1 were inhibited in a dose-dependent manner by selective LAT1 inhibitors (2-amino-2-norbornane-carboxylic acid, BCH and melphalan, LPM). Inhibitory growth activities of various conventional anti-cancer drugs, including carboplatin, cyclophosphamide, dacarbazine, doxorubicin, mitoxantrone, nimustine, vinblastine and vincristine, were significantly (P < 0.05) enhanced by combination use with BCH or LPM. These findings suggest that LAT1 could be a new therapeutic target for MM.

Fukumoto, Shinya; Hanazono, Kiwamu [Veterinary Internal Medicine, Department of Small Animal Clinical Sciences, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501 (Japan)] [Veterinary Internal Medicine, Department of Small Animal Clinical Sciences, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501 (Japan); Fu, Dah-Renn; Endo, Yoshifumi; Kadosawa, Tsuyoshi [Veterinary Oncology, Department of Small Animal Clinical Sciences, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501 (Japan)] [Veterinary Oncology, Department of Small Animal Clinical Sciences, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501 (Japan); Iwano, Hidetomo [Veterinary Biochemistry, Department of Basic Veterinary Medicine, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501 (Japan)] [Veterinary Biochemistry, Department of Basic Veterinary Medicine, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501 (Japan); Uchide, Tsuyoshi, E-mail: uchide@rakuno.ac.jp [Veterinary Internal Medicine, Department of Small Animal Clinical Sciences, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501 (Japan)] [Veterinary Internal Medicine, Department of Small Animal Clinical Sciences, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501 (Japan)

2013-09-13

302

Immunization with DISC1 protein in an animal model of ADHD influences behavior and excitatory amino acids in prefrontal cortex and striatum.  

PubMed

The Disrupted-in-schizophrenia 1 (DISC1) gene is involved in vulnerability to neuropsychiatric disorders. Naples high-excitability (NHE) rat model neuropsychiatric problems characterized by an unbalanced mesocortical dopamine system. Here, we assessed behavioral and neurochemical effects of immunization against multimeric rat DISC1 protein in adult NHE rats, an animal model of attention-deficit hyperactivity disorder and their Random-Bred (NRB) controls. Males of both lines received subcutaneous injections of vehicle (PB), adjuvant only (AD) or recombinant rat DISC1 protein purified from E. coli, suspended in AD (anti-DISC1) at age of 30, 45 and 60 postnatal days (pnd). At 75 pnd, the rats were exposed to a Làt maze and 2 days later to an Olton eight-arm radial maze, and horizontal (HA) and vertical activities (VA) were monitored. Non-selective (NSA) and selective spatial attention (SSA) were monitored in the Làt and in the Olton maze by duration of rearings and working memory, respectively. Post mortem neurochemistry in the prefrontal cortex (PFc), dorsal (DS) and ventral (VS) striatum of L-Glutamate, L-Aspartate and L-Leucine was performed. All immunized rats showed a clear humoral IgM (but not IgG) immune response against the immunogen, indicating that immunological self-tolerance to DISC1 can be overcome by immunization. NHE rats exhibited a higher unspecific IgM response to adjuvant, indicating an immunological abnormality. The sole anti-DISC1 immunization-specific behavioral in the NHE rats was an increased horizontal activity in the Làt maze. Adjuvant treatment increased vertical activity in both lines, but in the NRB controls it increased rearing and decreased horizontal activity. Liquid chromatography/tandem mass spectrometry analysis of soluble or membrane-trapped neurotransmitters aspartate, glutamate and leucine revealed increased soluble aspartate levels in the ventral striatum of NRB controls after anti-DISC1 immunization. Immune activation by adjuvant independent of simultaneous DISC1 immunization led to other specific changes in NHE and control NRB rats. In DISC1-immunized NHE rats, horizontal activity in Lat maze correlated with membrane-trapped glutamate in PFc and in the NRB rats, duration of rearing in Olton maze correlated with membrane-trapped glutamate in PFc and aspartate in dorsal striatum. In addition to non-specific immune activation (by AD), the postnatal anti-DISC1 immune treatment led to behavioral changes related to mechanisms of activity and attention and had influenced amino acids and synaptic markers in striatum and neocortex in the adult NHE as well as control animals. PMID:25595600

Ruocco, L A; Treno, C; Gironi Carnevale, U A; Arra, C; Boatto, G; Pagano, C; Tino, A; Nieddu, M; Michel, M; Prikulis, I; Carboni, E; de Souza Silva, M A; Huston, J P; Sadile, A G; Korth, C

2015-03-01

303

Neutral amino acid transport by membrane vesicles of Streptococcus cremoris is subject to regulation by internal pH.  

PubMed Central

The pH dependence of transport of the neutral amino acids L-serine and L-alanine by membrane vesicles of Streptococcus cremoris have been studied in detail. The rates of four modes of facilitated diffusion (e.g., influx, efflux, exchange, and counterflow) of L-serine and L-alanine increase with increasing H+ concentration. Rates of artificially imposed electrical potential across the membrane (delta psi)-driven transport of L-serine and L-alanine show an optimum at pH 6 to 6.5. Under similar conditions, delta psi- and pH gradient across the membrane (delta pH)-driven transport of L-leucine is observed within the pH range studied (pH 5.5 to 7.5). The effect of ionophores on the uptake of L-alanine and L-serine has been studied in membrane vesicles of S. cremoris fused with proteoliposomes containing beef heart mitochondrial cytochrome c oxidase as a proton motive force (delta p)-generating system (Driessen et al., Proc. Natl. Acad. Sci. USA 82:7555-7559, 1985). An increase in the initial rates of L-serine and L-alanine uptake is observed with decreasing pH, which is not consistent with the pH dependency of delta p. Nigericin, an ionophore that induced a nearly complete interconversion of delta pH into delta psi, stimulated both the rate and the final level of L-alanine and L-serine uptake. Valinomycin, an ionophore that induced a collapse of delta psi with a noncompensating increase in delta pH, inhibited L-alanine and L-serine uptake above pH 6.0 more efficiently than it decreased delta p. Experiments which discriminate between the effects of the internal pH and the driving force (delta pH) on solute transport indicate that at high internal pH the transport systems for L-alanine and L-serine are inactivated. A unique relation exists between the internal pH and the initial rate of uptake of L-serine and L-alanine with an apparent pK of 7.0. The rate of L-alanine and L-serine uptake decreases with increasing internal pH. The apparent complex relation between the delta p and transport of L-alanine and L-serine can be explained by a regulatory effect of the internal pH on the activity of the L-serine and L-alanine carriers. PMID:3108240

Driessen, A J; Kodde, J; de Jong, S; Konings, W N

1987-01-01

304

Acute effects of a commercially-available pre-workout supplement on markers of training: a double-blind study  

PubMed Central

Background Pre-workout supplements containing numerous ingredients claim to increase performance and strength. Product-specific research is important for identifying efficacy of combined ingredients. The purpose of this study was to evaluate the effects of a proprietary pre-workout dietary supplement containing creatine monohydrate, beta-alanine, L-Tarurine, L-Leucine, and caffeine, on anaerobic power, muscular strength, body composition, and mood states. Methods In a double-blind, randomized, matched-pair design, twenty male subjects (mean?±?SD; 22.4?±?9.5 yrs, 76.9?±?11.2 kg, 22.7?±?9.5% body fat), consumed either 30 g of a pre-workout supplement (SUP) or maltodextrin placebo (PLC) 30 minutes before a resistance training workout, after completing baseline testing. Body composition was determined via dual-energy x-ray absorptiometry (DEXA). Subjects completed 12 vertical jumps for height (VJ) and one repetition maximum (1RM) and repetitions to failure lifts on bench (BPM) and leg press (LPM). Finally, subjects completed a Wingate power test on a cycle ergometer [mean power (WMP) and peak power (WPP)]. After baseline testing, participants completed eight days of supplementation and four split-body resistance-training bouts. Side effect questionnaires were completed daily 30 minutes after consuming the supplement. Subjects completed post-supplement testing on Day 8. Data were analyzed utilizing a 2?×?2 repeated measures ANOVA [treatment (PLC vs SUP)?×?time (T1 vs T2)] and ninety-five percent confidence intervals. Results There were no significant treatment?×?time interactions (p?>?0.05). There were no significant changes in %body fat (%BF; ?-0.43?±?0.58; p?=?0.920), fat mass (?-2.45?±?5.72; p?=?0.988), or lean body mass (LBM; 10.9?±?12.2; p?=?0.848). 95% CI demonstrated significant LBM increases for both groups. There was a main effect for time for WPP (?100.5?±?42.7W; p?=?0.001), BPM (?8.0?±?12.9 lbs; p?=?0.001), and LPM (?80.0?±?28.8 lbs; p?=?0.001), with no significant differences between treatments. There was no significant difference in mood states between groups or over time. Conclusion The proprietary pre-workout blend combined with eight days of training did not significantly (ANOVA) improve body composition or performance. While not significant, greater gains in LPM were demonstrated in the SUP group for lean body mass and lower body strength. Future studies should evaluate more chronic effects of proprietary pre-workout blends on total training volume and performance outcomes. PMID:25302053

2014-01-01

305

Effect of Starvation on the Turnover and Metabolic Response to Leucine  

PubMed Central

l-Leucine was administered as a primed continuous 3-4-h infusion in nonobese and obese subjects in the postabsorptive state and for 12 h in obese subjects after a 3-day and 4-wk fast. In nonobese and obese subjects studied in the post-absorptive state, the leucine infusion resulted in a 150-200% rise in plasma leucine above preinfusion levels, a small decrease in plasma glucose, and unchanged levels of plasma insulin and glucagon and blood ketones. Plasma isoleucine (60-70%) and valine (35-40%) declined to a greater extent than other amino acids (P < 0.001). After 3 days and 4 wk of fasting, equimolar infusions of leucine resulted in two- to threefold greater increments in plasma leucine as compared to post-absorptive subjects, a 30-40% decline in other plasma amino acids, and a 25-30% decrease in negative nitrogen balance. Urinary excretion of 3-methylhistidine was however, unchanged. Plasma glucose which declined in 3-day fasted subjects after leucine administration, surprisingly rose by 20 mg/100 ml after 4 wk of fasting. The rise in blood glucose occurred in the absence of changes in plasma glucagon and insulin and in the face of a 15% decline in endogenous glucose production (as measured by infusion of [3-3H]glucose). On the other hand, fractional glucose utilization fell by 30% (P < 0.001), thereby accounting for hyperglycemia. The estimated metabolic clearance rate of leucine fell by 48% after 3 days of fasting whereas the plasma delivery rate of leucine was unchanged, thereby accounting for a 40% rise in plasma leucine during early starvation. After a 4-wk fast, the estimated metabolic clearance rate of leucine declined further to 59% below base line. Plasma leucine nevertheless fell to postabsorptive levels as the plasma delivery rate of leucine decreased 65% below postabsorptive values. Conclusions: (a) Infusion of exogenous leucine in prolonged fasting results in a decline in plasma levels of other amino acids, improvement in nitrogen balance and unchanged excretion of 3-methylhistidine, thus suggesting stimulation of muscle protein synthesis, (b) leucine infusion also reduces glucose production and to an even greater extent, glucose consumption, thereby raising blood glucose concentration; and (c) the rise in plasma leucine in early starvation results primarily from a decrease in leucine clearance which drops progressively during starvation. PMID:659610

Sherwin, Robert S.

1978-01-01

306

Prepuberal stimulation of 5-HT7-R by LP-211 in a rat model of hyper-activity and attention-deficit: permanent effects on attention, brain amino acids and synaptic markers in the fronto-striatal interface.  

PubMed

The cross-talk at the prefronto-striatal interface involves excitatory amino acids, different receptors, transducers and modulators. We investigated long-term effects of a prepuberal, subchronic 5-HT7-R agonist (LP-211) on adult behaviour, amino acids and synaptic markers in a model for Attention-Deficit/Hyperactivity Disorder (ADHD). Naples High Excitability rats (NHE) and their Random Bred controls (NRB) were daily treated with LP-211 in the 5th and 6th postnatal week. One month after treatment, these rats were tested for indices of activity, non selective (NSA), selective spatial attention (SSA) and emotionality. The quantity of L-Glutamate (L-Glu), L-Aspartate (L-Asp) and L-Leucine (L-Leu), dopamine transporter (DAT), NMDAR1 subunit and CAMKII?, were assessed in prefrontal cortex (PFC), dorsal (DS) and ventral striatum (VS), for their role in synaptic transmission, neural plasticity and information processing. Prepuberal LP-211 (at lower dose) reduced horizontal activity and (at higher dose) increased SSA, only for NHE but not in NRB rats. Prepuberal LP-211 increased, in NHE rats, L-Glu in the PFC and L-Asp in the VS (at 0.250 mg/kg dose), whereas (at 0.125 mg/kg dose) it decreased L-Glu and L-Asp in the DS. The L-Glu was decreased, at 0.125 mg/kg, only in the VS of NRB rats. The DAT levels were decreased with the 0.125 mg/kg dose (in the PFC), and increased with the 0.250 mg/kg dose (in the VS), significantly for NHE rats. The basal NMDAR1 level was higher in the PFC of NHE than NRB rats; LP-211 treatment (at 0.125 mg/kg dose) decreased NMDAR1 in the VS of NRB rats. This study represents a starting point about the impact of developmental 5-HT7-R activation on neuro-physiology of attentive processes, executive functions and their neural substrates. PMID:24709857

Ruocco, Lucia A; Treno, Concetta; Gironi Carnevale, Ugo A; Arra, Claudio; Boatto, Gianpiero; Nieddu, Maria; Pagano, Cristina; Illiano, Placido; Barbato, Fabiana; Tino, Angela; Carboni, Ezio; Laviola, Giovanni; Lacivita, Enza; Leopoldo, Marcello; Adriani, Walter; Sadile, Adolfo G

2014-01-01

307

Leucine-rich diet supplementation modulates foetal muscle protein metabolism impaired by Walker-256 tumour  

PubMed Central

Background Cancer-cachexia induces a variety of metabolic disorders of protein turnover and is more pronounced when associated with pregnancy. Tumour-bearing pregnant rats have impaired protein balance, which decreases protein synthesis and increases muscle breakdown. Because branched-chain amino acids, especially leucine, stimulate protein synthesis, we investigated the effect of a leucine-rich diet on protein metabolism in the foetal gastrocnemius muscles of tumour-bearing pregnant rats. Methods Foetuses of pregnant rats with or without Walker 256 tumours were divided into six groups. During the 20 days of the experiment, the pregnant groups were fed with either a control diet (C, control rats; W, tumour-bearing rats; Cp, rats pair-fed the same normoprotein-diet as the W group) or with a leucine-rich diet (L, leucine rats; LW, leucine tumour-bearing rats; and Lp, rats pair-fed the same leucine-rich diet as the LW group). After the mothers were sacrificed, the foetal gastrocnemius muscle samples were resected, and the protein synthesis and degradation and tissue chymotrypsin-like, cathepsin and calpain enzyme activities were assayed. The muscle oxidative enzymes (catalase, glutathione-S-transferase and superoxide dismutase), alkaline phosphatase enzyme activities and lipid peroxidation (malondialdehyde) were also measured. Results Tumour growth led to a reduction in foetal weight associated with decreased serum protein, albumin and glucose levels and low haematocrit in the foetuses of the W group, whereas in the LW foetuses, these changes were less pronounced. Muscle protein synthesis (measured by L-[3H]-phenylalanine incorporation) was reduced in the W foetuses but was restored in the LW group. Protein breakdown (as assessed by tyrosine release) was enhanced in the L and W groups, but chymotrypsin-like activity increased only in group W and tended toward an increase in the LW foetuses. The activity of cathepsin H was significantly higher in the W group foetuses, but the proteolytic calcium-dependent pathway showed similar enzyme activity. In parallel, an intense oxidative stress process was observed only in the group W foetuses. Conclusions These data suggested that the proteasomal and lysosomal proteolytic pathways and oxidative stress are likely to participate in the process of foetal muscle catabolism of Walker’s tumour-bearing pregnant rats. The present work shows that foetal muscle can be protected by supplementation with a leucine-rich diet. PMID:24383706

2014-01-01

308

Pt based enzyme electrode probes assembled with Prussian Blue and conducting polymer nanostructures.  

PubMed

Conductive polymer nanotubules of 1,2-diaminobenzene (1,2-DAB) were prepared using a porous polycarbonate membrane template, placed on a Pt foil and used to support the polymer, then, the electropolymerisation was performed by chronocoulometry. The obtained conductive polymer nanostructures were then placed on Pt electrode and used to support highly dispersed prussian blue (PB), which acts as the active component for H2O2 detection. The observed good stability of PB as catalyst of H2O2 was related to the presence of organic non-conventional conducting polymers in a composite nanostructured film. These nanostructured polymer/PB composite films were also characterised by scanning electron microscopy (SEM) and Raman spectroscopy. The non-conventional conducting polymer nanotubules/PB modified Pt electrodes were tested by cyclic voltammeter for stability at different pH values, then, by amperometry, for hydrogen peroxide, ascorbic acid, acetaminophen, uric acid and acetylcholine. Glucose oxidase (GOD), lactate oxidase (LOD), L-amino acid oxidase (L-AAOD), alcohol oxidase (AOD), glycerol-3-phosphate oxidase (GPO), lysine oxidase (LyOx), and choline oxidase (ChOx) were immobilised on PB layer supported on 1,2-diaminobenzene (1,2-DAB) nanotubules onto the Pt electrodes. Different strategies for enzyme immobilisation were performed and used. Analytical parameters such as reproducibility, interference rejection, response time, storage and operational stability of the sensors have been studied and optimised. Results provide a guide to design high sensitive, stable and interference-free biosensors. The glucose biosensors assembled with nanostructured poly(1,2-DAB) showed a detection limit of 5 x 10(-5) mol l(-1), a wide linearity range (5 x 10(-5) to 5 x 10(-3) mol l(-1)), a high selectivity, a stability of 3 months at 4 degrees C, and at least 4 weeks at room temperature. Similar analytical parameters and stability were also studied for L-(+)-lactic acid, L-leucine, ethanol, glycerol-3-phosphate, lysine, and choline biosensors. PMID:15556371

Curulli, A; Valentini, F; Orlanduci, S; Terranova, M L; Palleschi, G

2004-12-15

309

Hypercontractility of intestinal longitudinal smooth muscle induced by cytokines is mediated by the nuclear factor-?B/AMP-activated kinase/myosin light chain kinase pathway.  

PubMed

Recent studies have identified AMP-activated kinase (AMPK) as a target of Ca(2+)/calmodulin-dependent kinase kinase (CaMKK?) and a negative regulator of myosin light-chain (MLC) kinase (MLCK). The present study examined whether a change in expression or activity of AMPK is responsible for hypercontractility of intestinal longitudinal muscle during inflammation or in response to proinflammatory cytokines. In mouse colonic longitudinal muscle cells, acetylcholine (ACh) stimulated AMPK and MLCK phosphorylation and activity and induced MLC20 phosphorylation and muscle contraction. Blockade of CaMKK? with STO609 (7-oxo-7H-benzimidazo[2,1-a]benz[de]isoquinoline-3-carboxylic acid acetate) inhibited AMPK and MLCK phosphorylation and augmented MLCK activity, MLC20 phosphorylation, and smooth muscle cell contraction. In muscle cells isolated from the colon of TNBS (2,4,6-trinitrobenzenesulfonic acid)-treated mice or from strips treated with interleukin-1? or tumor necrosis factor-?, nuclear factor ?B was activated as indicated by an increase in p65 phosphorylation and I?B? degradation, and AMPK was phosphorylated at a cAMP-dependent protein kinase (PKA)-specific site (Ser(485)) that is distinct from the stimulatory CaMKK? site (Thr(172)), resulting in attenuation of ACh-stimulated AMPK activity and augmentation of MLCK activity and muscle cell contraction. Inhibition of nuclear factor-?B activity with MG-132 (carbobenzoxy-L-leucyl-L-leucyl-L-leucinal Z-LLL-CHO) or PKA activity with myristoylated PKA inhibitor 14-22 amide blocked phosphorylation of AMPK at Ser(485) and restored MLCK activity and muscle cell contraction to control levels. The results imply that PKA released from I?B? complex phosphorylated AMPK at a PKA-specific site and inhibited its activity, thereby relieving the inhibitory effect of AMPK on MLCK and increasing MLCK activity and muscle cell contraction. We conclude that hypercontractility of intestinal longitudinal muscle induced by inflammation or proinflammatory cytokines is mediated by nuclear factor ?B/PKA-dependent inhibition of AMPK and activation of MLCK. PMID:24769544

Nalli, Ancy D; Kumar, Divya P; Mahavadi, Sunila; Al-Shboul, Othman; Alkahtani, Reem; Kuemmerle, John F; Grider, John R; Murthy, Karnam S

2014-07-01

310

L-proline transport by purified cell types of lobster hepatopancreas.  

PubMed

The hepatopancreas of the American lobster, Homarus americanus, has four epithelial cell types that are anatomically distinguishable and can be separated for in vitro investigation of their individual biological roles in the intact organ using centrifugal elutriation. Previous studies employing this separation method have produced hepatopancreatic cell suspensions that have been used to examine the nature of copper transport, 2 Na+/1 H+ exchange, and D-glucose absorption by each cell type in isolation from the other cells comprising the tubular epithelium. The present investigation used this method to study amino acid transport by E-, F-, R-, and B-cells of the lobster hepatopancreas in order to characterize the absorption processes for protein digestion products by this organ and to identify which cell type was most likely the responsible agent for net transcellular transfer of these organic molecules from lumen to blood. Results indicated that heptopancreatic E- and F-cell types were the only cells exhibiting Na+-dependent 3H-L-proline transport. Further examination of 3H-L-proline influx by F-cell suspensions indicated that this cell type possessed plasma membrane Na+-dependent IMINO-like and B0-like transport mechanisms and Na+-independent L-like transport mechanisms. Using selective inhibitors of these separate transport systems (e.g., L-pipecolate, L-alanine, and L-leucine), the IMINO-like transporter appeared to predominate in L-proline influx into F-cells, while lesser amounts of amino acid transport took place by the B0-like and L-like systems. The results of this study suggest that the hepatopancreatic F-cell is the epithelial cell type responsible for the bulk of amino acid absorption by this organ and that the IMINO-like transporter is responsible for most of the L-proline transfer through this agent. It is further suggested that as digestion and absorption proceeds in the hepatopancreas and concentrations of luminal amino acids and sodium fall, Na+-dependent transport systems, like the IMINO-like and B0-like, increase their binding affinities for their substrates to maximize nutrient transfer across the epithelium. PMID:16823835

Fiandra, L; Mandal, P K; Giordana, B; Ahearn, G A

2006-10-01

311

Bat2p is essential in Saccharomyces cerevisiae for fusel alcohol production on the non-fermentable carbon source ethanol.  

PubMed

Branched-chain amino acids (BCAAs) are key substrates in the formation of fusel alcohols, important flavour components in fermented foods. The first step in the catabolic BCAA degradation is a transaminase step, catalyzed by a branched-chain amino acid transaminase (BCAAT). Saccharomyces cerevisiae possesses a mitochondrial and a cytosolic BCAAT, Bat1p and Bat2p, respectively. In order to study the impact of the BCAATs on fusel alcohol production derived from the BCAA metabolism, S. cerevisiae BCAAT-deletion mutants were constructed. The BCAA l-leucine was exogenously supplied during cultivations with mutants of S. cerevisiae. BAT1 deletion is not essential for fusel alcohol production, neither under glucose nor under ethanol growth conditions. The 3-methyl-1-butanol production rate of bat1Delta-cells on ethanol was decreased in comparison with that of wild-type cells, but the cells were still able to produce 3-methyl-1-butanol. However, drastic effects in fusel alcohol production were obtained in cells lacking BAT2. Although the constructed bat2Delta-single deletion strain and the bat1Deltabat2Delta-double deletion strain were still able to produce 3-methyl-1-butanol when grown on glucose, they were incapable of producing any 3-methyl-1-butanol when ethanol was the sole carbon source available. In the circumstances used, gene expression analysis revealed a strong upregulation of BAT2 gene activity in the wild type, when cells grew on ethanol as carbon source. Apparently, the carbon metabolism is able to influence the expression of BCAATs and interferes with the nitrogen metabolism. Furthermore, analysis of gene expression profiles shows that the expression of genes coding for other transaminases present in S. cerevisiae was influenced by the deletion of one or both BCAATs. Several transaminases were upregulated when a BCAAT was deleted. Strikingly, none of the known transaminases was significantly upregulated when BAT2 was deleted. Therefore we conclude that the expression of BAT2 is essential for 3-methyl-1-butanol formation on the non-fermentable carbon source, ethanol. PMID:15851104

Schoondermark-Stolk, Sung A; Tabernero, Maria; Chapman, John; Ter Schure, Eelko G; Verrips, C Theo; Verkleij, Arie J; Boonstra, Johannes

2005-05-01

312

Mechanistic studies on the aminopeptidase from Aeromonas proteolytica: a two-metal ion mechanism for peptide hydrolysis.  

PubMed

The aminopeptidase from Aeromonas proteolytica (AAP) is uncompetitively inhibited by fluoride ion at pH 8.0 with an inhibition constant (Ki) of 30 mM. Thus, fluoride inactivates AAP only after substrate binding, and only a single fluoride ion binds to AAP. On the other hand, chloride ion does not inhibit AAP up to concentrations of 2 M at pH 8.0. The pH dependence of fluoride inhibition of AAP was measured over the pH range 6.0-9.5. Between pH values of 6.0 and 9.0, fluoride ion acts as a pure uncompetitive inhibitor of AAP, and the Ki increases from 1.2 to 370 mM. From a plot of pKi vs pH, a pKa value of 7.0 +/- 0.3 was extracted which corresponds to a single deprotonation process. At pH values higher than 9.0, the fluoride inhibition pattern changes to competitive. This change in inhibition pattern was attributed to a change in ionic strength or perhaps pH of the solution since fluoride ion was also found to become a competitive inhibitor of AAP at pH 8.0 in the presence of 2 M NaCl. These data, taken together with previous kinetic studies of mono- and dinuclear hydrolases with fluoride ion, suggest that a Zn(II)-bound water/hydroxide exists at the dimetal active site of AAP with a pKa of 7.0 and that this water/hydroxide acts as the active site nucleophile. The hydrolysis of L-leucine-p-nitroanilide was measured spectrophotometrically in triplicate between 25 and 85 degrees C at eight substrate concentrations ranging from 5 to 800 microM. From these data, Km values were derived at each temperature studied and were found to increase exponentially with increasing temperature. Moreover, the calculated Vmax values were also found to increase over this temperature range, mimicking the Km values. An Arrhenius plot was constructed from k(cat) values and was found to be linear over the temperature range 25-85 degrees C, indicating that the rate-limiting step in AAP peptide hydrolysis is product formation and does not change as a function of temperature. From the slope of the line, the activation energy (Ea) was calculated to be 36.5 kJ/mol. The enthalpy and entropy of activation at 25 degrees C calculated over the temperature range 298-358 K were found to be 34.0 kJ/mol and -94.2 J/(mol x K), respectively. The free energy of activation at 25 degrees C was found to be 62.1 kJ/mol. Combination of the available X-ray crystallographic data with the present kinetic and thermodynamic results, as well as the previously reported kinetic and spectroscopic data, has allowed a detailed catalytic mechanism for AAP to be proposed. PMID:9100023

Chen, G; Edwards, T; D'souza, V M; Holz, R C

1997-04-01

313

Microbial functional diversity in a mediterranean forest soil: impact of soil nitrogen availability  

NASA Astrophysics Data System (ADS)

Beneficial or negative effects of N deposition on forest soil are strongly linked to the activity of microbial biomass and enzyme activities because they regulate soil quality and functioning due to their involvement in organic matter dynamics, nutrient cycling and decomposition processes. Moreover, because the ability of an ecosystem to withstand serious disturbances may depend in part on the microbial component of the system, by characterizing microbial functional diversity we may be able to better understand and manipulate ecosystem processes. Changes in the biodiversity of the soil microbial community are likely to be important in relation to maintenance of soil ecosystem function because the microbial communities influence the potential of soils for enzyme-mediated substrate catalysis. Objective of this study was to evaluate how soil N availability affected microbial functional diversity in a 4 months laboratory experiment. The incubation experiment was carried out with an organo-mineral soil collected in a Quercus cerris forest at the Roccarespampani site (Central Italy, Viterbo). All samples were incubated at 28°C and were kept to a water content between 55 and 65% of the water holding capacity. Different amount of N (NH4NO3) were added as solution once a week in order to mimic the N wet deposition and to let microbial community deal with a slow increase in time of inorganic N content. The amount of nutrient solutions was chosen depending on the average soil-water loss due to evaporation in one week. The total amount of N-NH4NO3 was chosen to be comparable with the range of N depositions currently reported in European forests, i.e. between 1 and 75 kg N ha-1 y-1. The total amount added at the end of incubation varied from 0, 10, 25, 50 and 75 kg N ha-1. Distilled water was added in the control soil in order to provide the same amount of solution as the treated soils. In order to discriminate the effect of N, the NH4NO3 solutions were adjusted to soil pH and phosphorus was added in order to prevent any nutrient limitation effect. In this experiment microbial functional diversity was assessed at the community level with two independent approaches: the first one uses soil hydrolytic and oxidative enzymes and the second one C substrates utilization rates with the MicroResp system. The activities of important soil enzymes involved in organic matter and nutrient transformations were determined using a fluorimetric approach: beta-glucosidase, alfa-glucosidase, beta-xylosidase and beta-cellobiohydrolase activities are key enzymes in the cellulose and starch degradation; N-acetyl-?-glucosaminidase and leucine-aminopeptidase activities are involved in N cycling through chitin degradation, a major source of mineralizable N in soil and peptides release; acid phosphatase is crucial in organic P transformation; butyric esterase is an indicator of the physiological performance of microbial biomass in soil. (Poly)phenol oxidative activity was determined spectrophotometrically as an indicator of lignin and lignin-like substances polymerization and depolymerization. All enzymes were assessed at the beginning of the incubation and after 6, 13, 26, 42, 55, 83 and 118 days. For the MicroResp method C substrates for the analysis of Community Level Physiological Profile (CLPP) were selected depending on their ecological relevance and the objective of the experiment. C sources include four carbohydrates (Alpha-D-glucose, N-acetyl-Glucosamine, D-Galactose, D-fructose), four amino acids (L-arabionose, L-leucine, L-arginine, Glycine), five carboxylic acid (Malic acid, citric acid, Oxalic acid, L-aspartic acid and gamma-amino-butyric acid) and two phenolic acids (vanillic acid and syringic acid). MicroResp analysis was performed at the beginning and at the end of the incubation. Discriminant function analysis and Shannon diversity index were used to determine microbial functional diversity with the two different approaches.

Dalmonech, D.; Lagomarsino, A.; Moscatelli, M. C.

2009-04-01