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PubMed1975

Production, purification, and characterization of an extracellular chitosanase from Streptomyces.

The synthesis by Streptomyces sp. no. 6 of an extracellular chitosanase was induced by glucosamine. The enzyme was purified to homogeneity by Sephadex G-100, carboxymethyl-cellulose, and diethylaminoethyl-cellulose chromatography. The purified enzyme hydrolyzed chitosan (the beta-1,4-linked polymer of glucosamine) but not chitin nor carboxymethyl-cellulose. The only products of the hydrolysis detectable by paper chromatography were di- and triglucosamine. Sephadex G-100 chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the molecular weight of the enzyme was between 29,000 and 26,000. Acid hydrolysates of the enzyme contained no cysteic acid or glucosamine or other carbohydrate. At 25 C, maximum activity was obtained between pH 4.5 and 6.5. The enzymatic hydrolysis of chitosan occurred over a wide range of temperatures and was maximal at 60 C. The rate of the reaction was inhibited by concentrations of soluble chitosan higher than 0.5 g/liter. The apparent Km calculated from a Lineweaver-Burke plot was 0.688 g/liter at pH 5.5. The enzyme prevented spore germination and caused a significant decrease in the turbidity of germinated spore suspensions of the Mucor strains tested. Such a decrease was the result of a partial lysis of the cell wall.

Amino Sugars↗
PubMedDate not supplied

Transport of L-citrulline in neural cell cultures.

Uptake of L-[(14)C]citrulline was studied in cell culture models of the main neural cell populations, in astroglia-rich primary cultures derived from neonatal rat brain, in rat glioma cells C6-BU-1, in cells of the murine microglial clone N11 and in the glioma x neuroblastoma hybrid cell line 108CC15 with neuronal properties. For comparison, cells of the peripheral macrophage cell line RAW 264.7 were also investigated. A saturable component of uptake was found in all cases with K(M) values between 0.4 and 3.4 mM and V(max) values between 15 and 35 nmol.min(-1).(mg protein)(-1). A nonsaturable component dominated uptake at high concentrations of extracellular citrulline. Rates of uptake of L-citrulline were not affected when Na(+) or Cl(-) were omitted from the incubation medium or in the presence of depolarizing concentrations of K(+). Saturable uptake of citrulline was strongly inhibited by an excess of histidine or beta-2-aminobicyclo-(2.2.1)-heptane-2-carboxylic acid; excess amounts of arginine, creatine, glutamate, cysteic acid or N-methyl-alpha-aminoisobutyric acid did not reduce citrulline uptake. Preincubation of the cells with bacterial lipopolysaccharide and interferon gamma did not stimulate transport of citrulline. The results suggest that at physiological concentrations citrulline is taken up by neural cells with the help of transport system L for large neutral amino acids. Therefore, in the brain, effective utilization of extracellular citrulline as part of an intercellular trafficking of intermediates of an NO/citrulline cycle depends on the concentrations of all neutral amino acids present.

Animals↗
PubMed2006

Discovery of potential sorbitol dehydrogenase inhibitors from virtual screening.

Sorbitol dehydrogenase (SDH) is the second enzyme in the polyol pathway of glucose metabolism and is a possible target for the treatment of the complications of diabetes. In this study the molecular modelling program DOCK was used to analyse 249,071 compounds from the National Cancer Institute Database and predict those with high affinity for SDH. From a total of 21 tested the 7 compounds including flavin adenine dinucleotide disodium hydrate, (+)-Amethopterin, 3-hydroxy-2-napthoic(2-hydroxybenzylidene) hydrazide, folic acid, N-2,4-dinitrophenyl-L-cysteic acid, Vanillin azine and 1H-indole-2,3-dione,5-bromo-6-nitro-1-(2,3,4-tri-O-acetyl-alpha-L-arabinopyranosyl)-(9Cl), were shown to inhibit SDH and displayed IC50 values of 0.192 microM, 1.1 microM, 1.2 microM, 4.5 microM, 5.3 microM, 7 microM and 28 microM, respectively. These compounds may aid the design of pharmaceutical agents for the treatment of diabetes complications.

Database Management Systems↗
PubMed1977

A peptide containing aspartic acid, glutamic acid and serine in calf brain synaptic vesicles.

Free amino acids and other amino compounds in calf brain synaptic vesicles were identified and determined by thin-layer chromatography and ion-exchange chromatography. The vesicles contained ten identified amino acids with glutamic acid, aspartic acid, taurine and gamma-aminobutyric acid in the highest concentrations, and also cysteic acid (or cysteinesulfinic acid), glutamine, alanine, serine, glycine and lysine. The vesicles also contained certain unknown acid-labile, ninhydrin-positive compounds, one of which was a peptide yielding, after acid hydrolysis, about 40% aspartic acid, 30% serine, 15% glutamic acid, 10% glycine and possibly some alanine and lysine. The concentration of the peptide in the vesicles was as high as that of all the other amino compounds together.

Amino Acids↗
PubMed1975

Purification, properties, and crystallographic data for a principal nontoxic lectin from seeds of Abrus precatorius.

Nontoxic abrus lectin has been prepared by a new purification procedure. The method is accomplished by 45% saturation ammonium sulfate fractionation from a 5% acetic acid extract of the seeds of Abrus precatorius followed by diethylaminoethyl-Sephadex A-50 and Sepharose 4B affinity chromatography. The abrus lectin appeared homogeneous as judged by electrophoresis, analytical ultracentrifugation, and isoelectric focusing. The lectin molecule has a weight of 126,000 as determined by sedimentation equilibrium. It is composed of four subunits, of which two pairs have either identical or closely similar molecular sizes (33,800 and 32,200 daltons) as revealed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The results of amino acid analyses are given; none of the cysteic acid appears to arise from cysteine. An electrofocusing experiment indicated the isoelectric point to be 5.0. Crystals large enough for x-ray investigation were obtained by a vapor diffusion technique. X-ray precession photographs revealed that abrus lectin crystallizes in a tetragonal unit cell of symmetry P41212 and dimensions a = 140 and c = 210 A. The asymmetric unit contains 2 protein molecules of molecular weight 126,000 and has a solvent content of approximately 41% by volume.

Amino Acids↗
PubMed1975

Synthesis of sulphoquinovosyl diacylglycerol by higher plants.

The biosynthesis of sulphoquinovosyl diacylglycerol in germinating alfalfa seeds has been examined. Some incorporation of [35S]sulphate into the lipid occurs before chlorophyll production anh this is unaffected by chloramphenicol. Cysteic acid, molybdate, sulphite and sulpholactic acid all reduce incorporation of [35S]sulphate into sulphoquinovosyl diacylgylcerol. Some comparisons are made with other seed types. The results indicate that sulphoquinovosyl diacylgylcerol synthesis in alfalfa probably proceeds by a pathway similar to that in Euglena.

Acetates↗
PubMed1997

Protein oxidation of a hair sample kept in Alaskan ice for 800-1000 years.

Ancient finds of organic matter are not only of the highest value for palaeochemists and palaeobiologists but can be used to determine basic chemical reactions, such as protein oxidation, over long time periods. We studied oxidation of human hair protein about one thousand years old of an Alaskan child buried in ice, ten hair samples of copts of comparable age buried in graves of hot dry sand and compared the results to ten recent hair samples. Protein oxidation parameters o-tyrosine and cysteic acid of the Alaskan child were comparable to recent samples whereas they were higher in the coptic specimen. N-epsilon-carboxymethyllysine, a parameter for glycoxidation, however, was as high in coptic specimen. We conclude that ice in contrast to soil prevented protein oxidation but failed to inhibit glycoxidation, a reaction initiated by autooxidation of glucose. This study therefore has implications for the interpretation of oxidation and glycoxidation as well as preservation mechanisms of proteins.

Alaska↗
PubMed1995

Evaluation and modification of an assay procedure for cysteine dioxygenase activity: high-performance liquid chromatography method for measurement of cysteine sulfinate and demonstration of physiological relevance of cysteine dioxygenase activity in cysteine catabolism.

Conflicting reports in the literature of appropriate assay procedures for measurement of cysteine dioxygenase activity led us to evaluate the procedure for assay of cysteine dioxygenase activity in rat liver preparations. Cysteine dioxygenase activity was largely in the soluble fraction of liver and was stimulated by addition of NAD+ and Fe2+. The pH optimum of the enzyme was 6.1. Addition of an inhibitor of pyridoxal 5-phosphate-dependent enzymes was necessary to prevent rapid removal of the reaction product cysteine sulfinate. Cysteine sulfinate and cysteic acid were separated by anion-exchange HPLC on a polymer-based column with trimethylamino active groups, and the reaction products were quantitated by measurement of 35S radioactivity or by formation and measurement of fluorescent derivatives. This assay of cysteine dioxygenase under optimal conditions provides a physiologically relevant measure of cysteine dioxygenase activity in liver and hepatocytes based on the observation that this activity was highly correlated with the capacity for cysteine catabolism and taurine production by isolated hepatocytes.

Animals↗
PubMed1992

Inhibitory effect of diet related sulphydryl compounds on the formation of carcinogenic nitrosamines.

N-Nitroso compounds (NOCs) are known to be strong carcinogens in various animals including primates (Preussman and Stewart, (1984) N-Nitroso Compounds). Human exposure to these compounds can be by ingestion or inhalation of preformed NOCs or by endogenous nitrosation from naturally occurring precursors (Bartsch and Montesano, Carcinogenesis, 5 (1984) 1381-1393; Tannebaum (1979) Naturally Occuring Carcinogens, Mutagens and Modulators of Carcinogenesis; Shephard et al., Food Chem. Toxicol., 25 (1987) 91-108). Several factors present in the diet can modify levels of endogenously formed nitrosamines by acting as catalysts or inhibitors. Compounds in the human diet that alter nitrosamine formation would thus play an important role in carcinogenesis study. Earlier researchers have reported the nitrite scavenging nature of sulphydryl compounds (Williams, Chem. Soc. Rev., 15 (1983) 171-196). We therefore studied the modifying effect of sulphydryl compounds viz., cysteine (CE), cystine (CI), glutathione (GU), cysteamine (CEA), cystamine (CEI), cysteic acid (CIA) and thioglycolic acid (TGA) on the nitrosation of model amines viz., pyrrolidine (PYR), piperidine (NPIP) and morpholine (NMOR). Many of these compounds are present in the food we consume. The present work also describes the inhibitory effect of onion and garlic juices on the nitrosation reactions. Both onion and garlic are known to contain sulphur compounds (Block, Sci. Am., 252 (1985) 114-119). Most of these compounds behave as antinitrosating agents and their inhibitory activity towards formation of carcinogenic nitrosamines, under different conditions is described.

Allium↗
PubMedDate not supplied

[Substrate specificity of cysteine lyase].

Substrate specificity is studied of cysteine lyase, a phosphopyridoxal-dependent enzyme belonging to the subgroup of beta-replacing lyases. This enzyme has a narrow specificity for the amino substrate; its only primary substrate is L-cysteine. Cysteine lyase has a broad specificity for the cosubstrate (replacing agent), catalysing the synthesis of L-cysteic acid from L-cysteine and sulfite ion or cystein thioesters (in the presence of some thiols). Enzyme is incapable to use alpha-phenyl- and alpha-methylcysteine as substrates. It is found that enzyme catalyses the exchange of alpha-H atoms of the aminoacid substrate cysteine with 3H2O. It does not catalyse alpha-hydrogenexchange in close structural analogues of substrate: L-alanine, D-serine, treonine, allo-threonine and 3-phosphoserine. L-Serine inhibited the synthesis of S-hydroxyethylcystein from cysteine and beta-mercaptoethanol (Ki of L-serine is 0,8-10(-2) M), participating at the first stage of reaction: the formation of a pyridoxylidenic derivative, which does not undergo the further alpha,beta-elimination of beta-replacement reactions.

Animals↗
PubMed2006

Differential pulse voltammetric determination of nimesulide in pharmaceutical formulation and human serum at glassy carbon electrode modified by cysteic acid/CNTs base on electrochemical oxidation of L-cysteine.

Carbon nanotubes (CNTs) and cysteic acid based on electrochemical oxidation of L-cysteine (CySH) to form a novel composite thin film material at a glassy carbon electrode (GCE) for electroanalytical determination of nimesulide. The determination of nimesulide at the composite modified electrode with strong accumulation of nimesulide was studied by differential pulse voltammetry (DPV). The peak current obtained at +1.251 V (versus SCE) from DPV was linearly dependent on the nimesulide concentration in the range of 1.0 x 10(-7) -1.0 x 10(-5) M in 0.05 M H(2)SO(4) solution with a correlation coefficient of 0.997. The detection limit (S/N = 3) was found to be 5.0 x 10(-8) M. The low-cost modified electrode showed good sensitivity, selectivity, stability and had been applied to the determination of nimesulide in pharmaceutical formulation and human serum samples with satisfactory results.

Carbon↗
PubMed1986

Plasma levels and renal handling of endogenous amino acids in snakes: a comparative study.

Plasma levels of 22 endogenous amino acids were measured by ion-exchange chromatography in four species of snakes: Thamnophis sirtalis, T. radix, Aipysurus laevis, and Python molurus. Despite considerable interspecific variation in the amino acid composition, all species showed relatively high plasma concentrations of histidine, a feature apparently unique to reptiles. The renal handling of these amino acids was studied by renal clearance methods. As in other vertebrates, net tubular absorption of filtered amino acids predominated. However, net tubular secretion of taurine, cysteic acid and/or phosphoserine and beta-alanine was observed, with taurine being the predominant amino acid secreted. The percentage reabsorption of the total amino acids filtered by the snake kidneys ranged from 79 to 95%. Evidence for the postrenal absorption of amino acids in these reptiles is presented. In species that normally undergo hibernation (Thamnophis spp.), the ability of the kidney to reabsorb amino acids was depressed by cold acclimation. Cold acclimation significantly decreased plasma levels of all amino acids except taurine, whose concentration increased. The increase in plasma taurine level may have resulted from cellular osmoregulation. Under these conditions, renal excretion of taurine increased concomitantly with the increase in plasma taurine concentration.

Amino Acids↗
PubMed1991

Location of the disulfide bonds in the antitumor protein neocarzinostatin.

Two disulfide bonds in the antitumor antibiotic neocarzinostatin were determined chemically. The peptic and peptic/thermolytic peptides from the native protein were isolated by gel filtration and ion-exchange chromatography followed by reverse-phase HPLC. The cystine peptides obtained were oxidized separately by performic acid treatment and further separated by HPLC into cysteic acid peptides. Sequence analyses of the isolated peptides revealed the location of the disulfide bonds at Cys37-Cys47 and Cys88-Cys93.

Amino Acid Sequence↗
PubMed1982

Cysteine sulfinic acid in the central nervous system: uptake and release of cysteine sulfinic acid by a rat brain preparation.

Uptake and release of cysteine sulfinic acid by synaptosomal fractions (P2) and slices of rat cerebral cortex were investigated. The P2 fraction had a Na+-dependent high-affinity uptake system for cysteine sulfinic acid (Km, 12 microM), which was restricted to the synaptosomes. High-affinity uptake of cysteine sulfinic acid was competitively inhibited by glutamate, aspartate, and cysteic acid. None of the various centrally acting drugs tested specifically inhibited this transport system. Release of [14C]cysteine sulfinic acid from preloaded cortical slices or P2 fractions was examined by a superfusion method, which avoided reuptake of released [14C]cysteine sulfinic acid. High K+ (56 mM) and veratridine (10 microM) stimulated the release of cysteine sulfinic acid from slices and the P2 fraction in a partly Ca2+-dependent manner. Diazepam at concentrations of 10 and 100 microM markedly inhibited the stimulated release, but not the spontaneous release, by cortisol slices. On the contrary, it had no effect on the stimulated release of cysteine sulfinic acid from the P2 fraction.

Animals↗
PubMed1988

Reversed-phase high-performance liquid chromatography technique for taurine quantitation.

Taurine (2-aminoethanesulfonic acid) was quantitated by reversed-phase chromatography on a C18 Resolve column using a linear gradient of 9-11% methanol in water. Glutamine was used as the internal standard. Pre-column derivatization of the amino acid with o-phthalaldehyde allowed the detection of as little as 0.1 pmol taurine. Dual ion-exchange column chromatography was employed to remove other amino acids and metabolic precursors of taurine from the samples. Cysteic acid and cysteine sulfinic acid did not interfere with taurine analysis by the high-performance liquid chromatographic method. For sample deproteinization, boiling and picric acid precipitation were used. Recovery of taurine averaged 93.5 +/- 5.0% (means +/- standard error of the mean) from standard solutions and was not affected by the method of deproteinization. Using this procedure, plasma taurine concentrations for the rat and chick were determined to be 100.7 +/- 13.1 microM and 108.0 +/- 0.3 microM, respectively. Recovery of taurine from plasma samples averaged 97.2 +/- 4.7%.

Animals↗
PubMed2005

Oxidation of hypotaurine and cysteine sulphinic acid by peroxynitrite.

Peroxynitrite mediates the oxidation of the sulphinic group of both HTAU (hypotaurine) and CSA (cysteine sulphinic acid), producing the respective sulphonates, TAU (taurine) and CA (cysteic acid). The reaction is associated with extensive oxygen uptake, suggesting that HTAU and CSA are oxidized by the one-electron transfer mechanism to sulphonyl radicals, which may initiate an oxygen-dependent radical chain reaction with the sulphonates as final products. Besides the one-electron mechanism, HTAU and CSA can be oxidized by the two-electron pathway, leading directly to sulphonate formation without oxygen consumption. The apparent second-order rate constants for the direct reaction of peroxynitrite with HTAU and CSA at pH 7.4 and 25 degrees C are 77.4+/-5 and 76.4+/-9 M(-1).s(-1) respectively. For both sulphinates, the apparent second-order rate constants increase sharply with decrease in pH, and the sigmoidal curves obtained are consistent with peroxynitrous acid as the species responsible for sulphinate oxidation. The kinetic data, together with changes in oxygen uptake, sulphinate depletion, sulphonate production, and product distribution of nitrite and nitrate, suggest that oxidation of sulphinates by peroxynitrite may take place by the two reaction pathways whose relative importance depends on reagent concentrations and pH value. In the presence of bicarbonate, the direct reaction of sulphinates with peroxynitrite is inhibited and the oxidative reaction probably involves only the radicals *NO2 and CO3*-, generated by decomposition of the peroxynitrite-CO2 adduct.

Bicarbonates↗
PubMed1985

Further characterization of human eosinophil peroxidase.

The large and the small subunits (Mr 50 000 and 10 500 respectively) of human eosinophil peroxidase were isolated by gel filtration under reducing conditions. The subunits were very strongly associated but not apparently cross-linked by disulphide bridges. During storage, the large subunit tended to form aggregates, which required reduction to dissociate them. Amino acid analysis of the performic acid-treated large subunit showed the presence of 19 cysteic acid residues. The small subunit of eosinophil peroxidase had the same Mr value as the small subunit of myeloperoxidase. However, although these subunits have very similar amino acid compositions, they showed different patterns of peptide fragmentation after CNBr treatment. The carbohydrate of eosinophil peroxidase seemed associated exclusively with the large subunit and comprised mannose (4.5%, w/w) and N-acetylglucosamine (0.8%, w/w). The far-u.v.c.d. spectrum of the enzyme indicated the presence of relatively little ordered secondary structure.

Amino Acids↗
PubMed1981

Identification of N-monoacetylcystine in uraemic plasma.

1. An unidentified ninhydrin-positive substance of an acidic nature was detected in the plasma of uraemic patients. This substance was isolated from haemodialysate by ion-exchange chromatography and gel filtration, and identified as a sulphur-containing amino acid: N-monoacetylcystine. 2. The quantitative determination of sulphur amino acids in plasma revealed that the plasma levels of cysteic acid, homocysteic acid, taurine, cystine and cystathionine as well as N-monoacetylcystine in uraemic patients were markedly higher than in normal subjects (P less than 0.001 for each). However, the plasma levels of methionine in uraemic patients were within normal limits.

Amino Acids, Sulfur↗