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At least 19 recordsLinked to original sources
PubMed1978

Rat liver cysteine dioxygenase (cysteine oxidase). Further purification, characterization, and analysis of the activation and inactivation.

Rat liver cysteine dioxygenase has been purified to homogeneity. It is a single subunit protein having a molecular weight of 22,500 +/- 1,000, with a pI of 5.5. The enzyme purified was catalytically inactive and activated by anaerobic incubation with either L-cysteine or its analogues such as carboxymethyl-L-cysteine, carboxyethyl-L-cysteine, S-methyl-L-cysteine, D-cysteine, cysteamine, N-acetyl-L-cysteine, and DL-homocysteine. The enzyme thus activated with L-cysteine was rapidly inactivated under aerobic condition. This rapid inactivation was observed at 0 degrees C where no formation of either the reaction product cysteine sulfinate or the autoxidation product of cysteine, cystine, was detected. Further analysis shows that the inactivation of the activated enzyme was due to oxygen but unrelated to either the presence of substrate, enzyme turnover or accumulation of inhibitor produced during assay. A distinct rat liver cytoplasmic protein, called protein-A, could completely prevented the enzyme from the aerobic inactivation. The loss of activity during assay in the absence of protein-A was shown to be a first order decay process. From the plots of log(deltaproduct/min) versus time, the initial velocity (VO) and the velocity at 7 min (V7) were obtained. The apparent Km value for L-cysteine in the absence of protein-A was calculated from the initial velocity as 4.5 X 10(-4)M. Protein-A did not alter the apparent Km value for L-cysteine. The chelating agents such as o-phenanthroline, alpha,alpha'-dipyridyl, bathophenanthroline, 8-hydroxyquinoline, EGTA, and EDTA strongly inhibited the enzyme activity when these chelating agents were added before preactivation. The purified cystein dioxygenase contains 1 atom of iron per mol of enzyme protein. By the activation procedure, the enzyme became less susceptible to the heat denaturation, the inhibitory effects of chelating agents and the tryptic digestion.

Animals↗
PubMedDate not supplied

Spinach threonine dehydratase. Inhibition by L-cysteine and D-cysteine.

L-threonine deaminase from spinach is inhibited by D- and L-cysteine. The inhibition patterns by D-cysteine and by L-cysteine are non-competitive. The value of Ki for D-cysteine and L-cysteine is of the same order of magnitude. Inhibitions by L-isoleucine and L-cysteine are additional. These results indicate that inhibition by L-cysteine occurs on a site of enzyme which is different from the binding site for L-isoleucine and L-valine. Probably L-cysteine and D-cysteine form the thiazolidinic ring with a PLP mole. Which is not costituent of the active site, but located in a different region.

Binding Sites↗
PubMed1977

Cystine content of legume seed proteins: estimation by determination of cysteine with 2-vinylquinoline, and relation to protein content and activity of cysteine synthase.

The cystine content of the protein of a number of different lines of legume seeds has been determined by the method of Krull et al. which selectively reacts cysteine residues of intact, reduced proteins with 2-vinylquinoline, giving an adduct with an absorption maximum at 318 nm. Some seed lines were found to have 3.5 times as much cysteine as the seed line with the lowest cysteine content, perhaps offering opportunities for improvement in the nutritional quality of bean seed proteins through breeding and selections. While no correlation between cysteine levels and protein content was observed, a positive correlation was found between the specific activity of the terminal enzyme of cysteine synthesis, cysteine synthase, and the cysteine content of seeds.

Cysteine↗
PubMed1975

Mutants of Salmonella typhimurium responding to cysteine or methionine: their nature and possible role in the regulation of cysteine biosynthesis.

Nineteen mutants of Salmonella typhimurium responding to either cysteine or methionine (cym) have been identified amongst cysteine (cys) and methionine (met) auxotrophs. Their growth responses to known intermediates in the related pathways of cysteine and methionine biosynthesis and complementation patterns in abortive transduction tests divided the mutants into six groups. Results of conjugation, cotransduction and deletion mapping experiments substantiated these groups, each of which carried a lesion within known cys genes. Enzyme assays on cym mutants from five of the six groups confirmed their cys gene deficiencies. Growth response and enzyme assay data were not consistent with mutants being leaky cys mutants (spared by methionine). None of eight cym mutants tested were able to convert [35S]methionine into [35S]cysteine. Selenate specifically inhibits the early enzymes of cysteine synthesis. In cym mutants this inhibition was relieved by cysteine but not by methionine, indicating that cym mutants require active cys enzymes for growth on methionine. There was evidence that methionine stimulated in vivo activity of cys enzymes in a cym mutant. Resistance to inhibition by 1,2,4-triazole results in reduced levels of the O-acetyl serine sulphydrylase. In cym mutants triazole resistance gave unstable suppression of the cym phenotype. Cym mutants may result from mutation in regulatory regions common to each of the cys genes, with the precise role of methionine as yet unknown.

Adenine Nucleotides↗
PubMed1978

Method of isolation of cysteine constitutive mutants of the cysteine regulon in Salmonella typhimurium.

A method for selection of constitutive cysB mutation is described which takes advantage of the resistance of cysteine constitutive mutants to 1,2,4-triazole. Since cysM cysK double mutants are cysteine auxotrophs, by selecting for triazole resistance in cysM strains, mutants arising under this condition also should be constitutive for cysteine biosynthesis. Genetic analysis of mutants isolated by this technique showed that their mutational sites are located in the cysB region. Biochemical assays of cysteine enzymes, sulphite reductase and O-acetylserine sulfhydrylase of the mutants showed the derepressed level of these enzymes and the lack or slight repression by 1-cysteine.

Cysteine↗
PubMed1976

Purification and some properties of rat liver cysteine oxidase (cysteine dioxygenase).

Cysteine oxidase (cysteine dioxygenase, EC 1.13.11.20) was purified approximately 1000-fold from rat liver. The purified enzyme (protein-B) was obtained as an inactive form, which was activated by anaerobic preincubation with L-cysteine. The active form of protein-B was inactivated during aerobic incubation to produce cysteine sulfinate. This inactivation of protein-B was protected by a distinct protein in rat liver cytoplasm, namely stabilizing protein (protein-A). The Ka and Km values for L-cysteine were 0.8-10(-3) M and 1.3-10(-3) M respectively. The enzyme was strongly inhibited by Cu+ and/or Fe2+ chelating agents but not by Cu2+ chelating agent. The optimum pH of enzyme reaction was 8.5-9.5 while that of enzyme activation was 6.8-9.5, with a broad peak.

Animals↗
PubMed1978

Decrease of rat liver cysteine dioxygenase (cysteine oxidase) activity mediated by glucagon.

The hepatic cysteine dioxygenase activity of rats was markedly decreased by the intraperitoneal administration of glucagon. The enzyme activity was also decreased by either dibutyryl cyclic AMP or theophylline. The prior administration of actinomycin D completely blocked the glucagon-mediated decrease of enzyme activity, while administrations of this inhibitor of protein synthesis after glucagon injection did not block the decrease of enzyme activity. A single administration of actinomycin D resulted in a slight increase of cysteine dioxygenase activity in the rat liver. On the other hand, the injection of cycloheximide resulted in a rapid decrease of the hepatic cysteine dioxygenase with a half-life of 2.5 h. The half-life of the enzyme in rat liver after glucagon administration was one hour. The administration of hydrocortisone or insulin had no effect on the glucagon-mediated decrease of cysteine dioxygenase of rat liver. The enzyme activity of alloxan diabetic rat liver was almost the same as that of the intact rat liver. The evidence obtained here suggests that enhancement of degradation or inactivation of cysteine dioxygenase is responsible for the glucagon-mediated decrease of the enzyme activity in rat liver.

Adrenal Glands↗
PubMed1978

Effects of L-cysteine, L-cysteine derivatives and ascorbic acid on lead excretion in rats.

Urinary and fecal excretion of lead in rats were compared after intravenous administration of L-cysteine and a number of its derivatives. In terms of increasing total lead excretion, L-cysteine ethyl ester was about half as effective as D-penicillamine, whereas L-cysteine and all other derivatives tested were only marginally effective. Interestingly, L-cysteine ethyl ester appeared to increase lead depletion mainly through biliary excretion. This compound may, therefore, have lower renal toxicity than other chelating agents which promote lead excretion principally by increasing urinary elimination. Dietary supplements containing 1% cysteine, 1% ascorbic acid of 1% of both substances did not dramatically increase lead elimination.

Animals↗
PubMed1975

Cysteine biosynthesis in Salmonella typhimurium: the presence of ATP-sulfurylase and APS-kinase in various cysteine-requiring mutants.

Enzymatic tests were performed on a series of cysteine-requiring mutants for the presence of the sulfate activating enzymes. ATP-sulfurylase (sulfate adenylyltransferase EC 2.7.7.4) and APS-kinase (adenylylsulfate kinase EC 2.7.1.25). The enzymatic products adenosine 5'-[35S]sulfatophosphate and adenosine 3'-phosphate 5'-[35S]sulfatophosphate were identified by paper electrophoresis and measured quantitatively without elution from the paper. Cys mutants mapping in cistrons, A, H, I, J, G, and Ea contain both enzymes. Mutation in the D cistron leads to the loss of ATP-sulfurylase. Mutants mapping in the C cistron lack APS-kinase. Ba, Bb, and Bc mutants lack both enzymes. The control of the synthesis of these enzymes by cysteine was examined. Both enzymes are missing when cells are grown on cysteine.

Adenosine Triphosphate↗
PubMed1977

[Cysteine--an essential amino acid? Biochemical thoughts about the position of cysteine in the metabolism of the premature neonate (author's transl)].

Liver cystathionase activity is absent in the fetal organism. This makes cysteine an essential amino acid for the prematurely born infant. The existing enzyme activity is shifting serine into DNA-synthesis. The placental transfer of cysteine from the mother to the fetus is decreased in comparison to other amino acids. A low fetal cysteine level is giving the shift to DNA-synthesis a further stimulation.

Amino Acids, Essential↗
PubMed1978

Chemical and biological characterization of different Tc complexes of cysteine and cysteine derivatives.

The labeling of cysteine and its derivatives (penicillamine, N-acetylcysteine, cysteine ethyl ester) with 99Tc (99mTc) was studied as a model for the radiopharmaceutical preparation of Tc-99m mercaptide complexes. After the use of TcO4-, TcOCl52-, and TcBr62- as labeling agents for the Tc oxidation states VII, V, and IV, respectively, complexes of Tc(V) and Tc(IV) were prepared and characterized. The biologic behavior of these complexes was studied in rats. The substitutions in cysteine are responsible for substantial changes of net charge and lipophilicity in the Tc complexes, and the consequences on the excretion patterns in Wistar rats are discussed.

Acetylcysteine↗
PubMed1976

[Thermal decomposition of cysteine, cystine, N-acetylcysteine, 4-thiazolidinecarboxylic acid and cysteine methyl ester in soy bean oil (authors transl)].

During the thermal decomposition of cysteine, cystine, N-acetylcysteine, 4-thiazolidinecarboxylic acid, cysteine methyl ester, in soy bean oil at 200 degrees C, a series of compounds containing sulphur are formed. Besides 15 alkylthiazoles, -thiazolines and -thiazolidines, compounds with 2 and 3 S-atoms can also be identified: ethane-1,2-dithiole, diethyldisulfide, diethyltrisulfide, 2-methyl-1,3-dithiolane, 1,2-dithiane, thialdine, 1,2,4-trithiolanes, 1,2,4-trithianes and 2-methyl-thiazolidino-(3,4-b-)-thiazolidine. N,N'-dibutyrylcystamine shows an antioxidant effect.

Acetylcysteine↗
PubMed1979

Cysteine auxotrophs of Salmonella typhimurium which grow without cysteine in a hydrogen/carbon dioxide atmosphere.

Cysteine auxotrophs of Salmonella typhimurium mutated in cysB, cysI or cysJ grew with sulphate as a sulphur source when incubated under a hydrogen/carbon dioxide atmosphere. Yields obtained under these conditions were equivalent to those characteristic of wild-type S. typhimurium. The same mutants failed to grow with sulphate as a sulphur source when incubated aerobically. Auxotrophs mutated in cysA, cysC, cysD, cysE, cysG and cysH required cysteine for growth under both incubation conditions. The results suggest that mutations in cysB (regulation of the several cys operons) and also cysI and cysJ (sulphite reductase activity) can be circumvented during anaerobic growth under hydrogen.

Anaerobiosis↗
PubMed1979

Dietary casein levels and taurine supplementation. Effects on cysteine dioxygenase and cysteine sulfinate decarboxylase activities and tuarine concentration in brain, liver and kidney of the rat.

Activities of cysteine dioxygenase (CO) and cysteine sulfinate decarboxylase (CSD) and the concentrations of taurine (T) in brain, liver and kidney of rats fed on diets containing 18% casein (A), 60% casein (B) and 17% casein supplemented with 1% of taurine (+T), were measured. Regardless of the diet, the three measurements were the same in the brains of the animals in the three groups. In the liver and the kidney, CO activity was also the same in all three diets, but a decrease of CSD activity associated to an increase of T was observed in rats fed on diet B. The taurine-supplemented diet led to an increase in T concentration.

Animals↗
PubMed1978

Cysteine oxidase and cysteine sulfinic acid decarboxylase in developing rat liver.

The patterns of development of cysteine oxidase (CO) and cysteine sulfinic acid decarboxylase (CSD) in rat liver are not similar. It was observed that CO is not under sex control as CSD is. The results obtained agree with the idea that, in liver, as well as in brain, CSD is the limiting factor for the regulation of taurine biosynthesis.

Age Factors↗