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PubMed1979

Tissue and regional distribution of cysteic acid decarboxylase. A new assay method.

A sensitive and rapid assay method method for cysteic acid decarboxylase was develped which combined the selectivity of ion exchange resin (a complete retention of the substrate, cysteic acid, and exclusion of the product, taurine) with the speed of a vacuum filtration. The synthesis and purification of 35S-labeled cysteic acid were described. The validity of the assay was established by the identification of the reaction product as taurine. With this new method, the decarboxylase activity was measured in discrete regions of bovine brain. Putamen had the highest activity, 172 pmol taurine formed/min/mg protein (100%), followed by caudate nucleus, 90%; cerebral cortex, 82%; hypothalamus, 81%; cerebellar cortex, 79%; cerebellar peduncle, 59%; thalamus, 42%; brain stem, 25%; pons, 10%; and corpus callosum, 3%. The decarboxylase activity in various mouse tissues was also determined as follows: liver, 403; brain, 145; kidney, 143; spinal cord, 59; lung, 21; and spleen, 10 pmol taurine formed/min/mg. No activity could be detected in skeleton muscle and heart, suggesting a different biosynthetic pathway for taurine synthesis in these tissues. The advantages and disadvantages of the new assay method are also discussed.

Animals↗
PubMed1995

Quantification of cysteine residues following oxidation to cysteic acid in the presence of sodium azide.

Quantification of cysteines by amino acid composition analysis is inaccurate because of decomposition of these residues during protein hydrolysis. Cysteine (and cystine) residues are oxidized to cysteic acid following hydrochloric acid hydrolysis in the presence of sodium azide. Using selected native and recombinant proteins, containing different numbers of cysteine residues, we investigated the conditions for the quantitative oxidation of cysteines to cysteic acid in the presence of sodium azide. Protein hydrolysis with hydrochloric acid in the presence of 0.20% sodium azide resulted in 87-100% oxidation of the cysteines to cysteic acid which was easily quantified. The results were highly reproducible so that the azide-induced oxidation can be used as a general method to determine cysteine residues in a given protein. The sodium azide-dependent oxidation is superior to oxidation with performic acid because (i) it can be performed in solution not requiring protein lyophilization and in approximately half of the time; (ii) it delivers slightly higher yields of cysteic acid; and (iii) it does not affect tyrosine residues, which can be modified during the performic acid treatment.

Amino Acids↗
PubMed2004

Efficient preparation of L-cysteic acid and its esters.

L-Cysteic acid and its esters were prepared in good yields from the oxidation of L-cystine by chlorine in water and in alcohols. When the reaction was carried out in alcohols the corresponding esters were produced.

Alcohols↗
PubMed1991

Oxidation of cysteine to cysteic acid in proteins by peroxyacids, as monitored by immobilized pH gradients.

It has often been debated whether the presence of persulfate in a polyacrylamide gel could lead to the oxidation of cysteine (Cys) in proteins to cysteic acid. In fact, direct incubation of bovine serum albumin (BSA) with peroxodisulfate and periodate barely alters the isoelectric point (pI) and does not produce any cysteic acid. In contrast, caroate (peroxomonosulfate) and perphthalate strongly lower the pI of BSA. In the former case it as demonstrated that 4-Cys (of a total of 35) were converted into cysteic acid. Perphthalate was found to be, by far, the strongest oxidant: 15 (of 35) Cys residues were oxidized to cysteic acid and all methionine groups were destroyed.

Ammonium Sulfate↗
PubMed1988

Reevaluation of taurine levels and distribution of cysteic acid decarboxylase in developing human fetal brain regions.

The possibilities of interference by glycerophosphoryl ethanolamine (GPE) in the estimation of taurine levels in cerebral cortex, midbrain, cerebellum, medullapons, and spinal cord of developing human fetal brain regions were eliminated by hydrolyzing tissue extracts with 6 M HCl. Cysteic acid thus produced was separated from taurine by ion-exchange chromatography using Biorad-AG resin. Fluorescamine was used as fluorogen. Data reveal that the estimation of taurine in human fetal brain regions is affected if GPE is present as a contaminant in the assay system. Cysteic acid decarboxylase activity was measured using cysteic acid as the substrate. Higher enzymic activity was recorded with increased fetal body weight, but the reverse was true for taurine level.

Body Weight↗
PubMed1976

Utilization of L-methionine sulfoxide, L-methionine sulfone and cysteic acid by the weanling rat.

Three experiments were conducted to test the ability of weanling rats to utilize the oxidized forms of the sulfur amino acids methionine and cysteine for growth. In the first two experiments, diets were fed which contained graded levels of methionine, methionine sulfoxide and methionine sulfone. The third experiment included a comparison of two dietary levels of cysteine and cysteic acid. The 2 week weight gain and food consumption data indicated that methionine sulfoxide was utilized for growth with only 60% of the efficiency of that achieved by rats fed methionine. Methionine sulfone was not utilized for growth. Analysis of plasma sulfur amino acids showed that the rat has a limited capacity to utilize methionine sulfoxide by effecting its reduction to methionine. Cysteic acid did not support weight gain. This amino acid appeared to be rapidly catabolized to taurine. It was concluded that methionine sulfone and cysteic acid cannot be utilized by the weanling rat. Methionine sulfoxide cannot fully meet the dietary requirement of the rat methionine because of its limited capacity to reduce this amino acid.

Amino Acids↗
PubMed1999

Effects of cysteic acid groups on the gas-phase reactivity and dissociation of [M + 4H]4+ ions from insulin chain B.

Gas-phase ion/molecule reactions and collision-induced dissociation (CID) were conducted on [M + 4H]4+ of insulin chain B. This Fourier transform mass spectrometry work involved ions from the oxidized peptide (with two cysteic acid residues) and its reduced form (with two cysteine residues). Kinetic behavior during deprotonation and hydrogen/deuterium exchange reactions indicates that insulin B (ox) ions have two distinct structural types. In contrast, insulin B (red) ions have only one major reacting population, which has a more compact structure than the oxidized ions. No significant differences in fragmentation patterns for the two insulin B (ox) populations were observed when CID was performed as a function of deprotonating reaction time. However, markedly different fragmentation was found between [M + 4H]4+ of insulin B (ox) and (red). Therefore, the presence of cysteic acid groups in insulin B (ox) significantly impacts dissociation and presumably structure. This suggests that some insulin B (ox) ions are zwitterionic, with the five basic sites protonated and one cysteic acid group deprotonated. Molecular dynamics calculations revealed several viable structures that are consistent with the experimental results. For example, the most stable form of the reduced ion, which is unprotonated at the His10, is very compact and has lost the alpha-helix of native insulin. Low energy structures for the oxidized ions include a zwitterion with an intraionic interaction between anionic Cyx7 and cationic His10, as well as a nonzwitterionic conformer that lacks a proton at Phe1; both structures retain the alpha-helix. These structures may account for the two experimentally observed isomers, although others are possible. In addition, experiments on oxidized insulin B were conducted from methanolic solution, which may denature the conformation, and pure aqueous solution, which may leave a native conformation. These differences in solvent composition had no effect on the gas-phase results.

Algorithms↗
PubMed1977

A sensitive radiometric assay for cysteic acid decarboxylase activity in crude enzyme preparations of rat liver and brain.

1. A method is described for the synthesis of L-[U-14C]cysteic acid from L-[U-14C] cysteine hydrochloride and for its subsequent utilisation as a substrate for cysteic acid decarboxylase activity in liver and brain. 2. The enzyme determination relies on the entrapment of radio-labelled carbon dioxide in Hyamine hydroxide. 3. The assay is sensitive, reliable and convenient and is particularly suitable for measuring the activity of the decarboxylase in crude enzyme preparations.

Animals↗
PubMed2002

Identification of phosphoserine and phosphothreonine as cysteic acid and beta-methylcysteic acid residues in peptides by tandem mass spectrometric sequencing.

Tandem mass spectrometry has long been an intrinsic tool to determine phosphorylation sites in proteins. However, loss of the phosphate moiety from both phosphoserine and phosphothreonine residues in low-energy collision-induced dissociation is a common phenomenon, which makes identification of P-Ser and P-Thr residues complicated. A method for direct sequencing of the Ser and Thr phosphorylation sites by ESI tandem mass spectrometry following beta-elimination/sulfite addition to convert -HPO4 to -SO3 has been studied. Five model phosphopeptides, including three synthetic P-Ser-, P-Thr-, or P-Ser- and P-Thr-containing peptides; a protein kinases C-phosphorylated peptide; and a phosphopeptide derived from beta-casein trypsin digests were modified and then sequenced using an ESI-quadrupole ion trap mass spectrometer. Following incubation of P-Ser- or P-Thr-containing peptides with Na2SO3/NaOH, 90% P-Ser and 80% P-Thr was converted to cysteic acid and beta-methylcysteic acid, respectively, as revealed by amino acid analysis. The conversion can be carried out at 1 microM concentration of the peptide. Both cysteic acid and beta-methylcysteic acid residues in the sequence were shown to be stable and easily identifiable under general conditions for tandem mass spectrometric sequencing applicable to common peptides.

Amino Acid Sequence↗
PubMed1990

Characteristics of Cl(-)-dependent L-[35S]cysteic acid transport into rat brain synaptic membrane vesicles.

Uptake of L-[35S]cysteic acid (L-CA) in rat synaptic membrane vesicles was investigated. Preincubation with either 10 mM L-glutamic acid (L-Glu), 25 mM L-CA, 10 mM DL-homocysteic acid, or 25 mM DL-2-amino-4-phosphonobutyrate on membrane vesicles enhanced L-[35S]CA and L-[3H]Glu uptake. Na+ (5 mM) and omission of Cl- from the assay medium decreased L-[35S]CA uptake into both 10 mM L-Glu-loaded and non-loaded membrane vesicles. The anion transport blockers, 4-acetamide-4'-isothiocyano-2,2'-disulfonic acid stilbene (SITS) and 4,4'-diisothiocyano-2,2'-disulfonic acid stilbene (DIDS), inhibited L-[35S]CA uptake in a dose-dependent manner. The maximal uptake rate for L-[35S]CA was decreased by 50 microM SITS, while the apparent Km value of L-CA was not changed. SITS increased the EC50 value of Cl- for L-[35S]CA uptake from 5 mM to 10 mM with reduction of the maximal effect. These results suggested that L-[35S]CA uptake into synaptic membrane vesicles was mediated by a SITS-sensitive hetero-exchange transport with non-labeled substrates.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1980

Stimulation of LH and FSH secretion following intraventicular injection of cysteic acid but not taurine.

Taurine and related neurally active metabolites, were tested for their ability to influence basal secretion of luteinizing hormone (LH) and follicle stimulating hormone (FSH). The animal model used was the unanesthetized, unrestrained adult rat with an indwelling catheter in the jugular vein and a cannula implanted in the right lateral cerebroventricle or anterior pituitary. The proposed inhibitory neurotransmitter traurine, and its metabolic precursor, hypotaurine, did not affect the secretion of LH or FSH following infusion of 0.2 or 2.0 mumol intraventricularly or into the pituitary. In contrast, intraventricular injection of cysteic acid, a neurally excitant amino acid, in doses of 2.0 and 0.2 mumol promoted pituitary secretion of LH in both male and female rats. FSH secretion was also increased slightly by cysteic acid (2.0 mumol). These studies provide additional evidence that excitatory amino acids have a stimulatory role in the release of pituitary gonadotropins.

Amino Acids, Sulfur↗
PubMed1976

Keratin decomposition by dermatophytes. II. Presence of s-sulfocysteine and cysteic acid in soluble decomposition products.

The dermatophyte Microsporum gypseum was grown on human hair in a mineral medium. Filtrates of cultures of various age were chromatographed on Sephadex gels and further characterized by chemical analysis and thin-layer chromatography. The products of keratin decomposition were separated into two fractions. The first fraction formed 10 to 20% of the bulk and contained proteins low in sulfur content. The second, very wide fraction contained oligopeptides and polypeptides with molecular weights from several hundreds up to approximately 13,000 with a peak at 1,000-2,000 daltons. This fraction contained a relatively high amount of cystine, S-sulfocysteine, and cysteic acid. S-sulfocysteine was present in the free state and also combined in peptides where its amount exceeded that of cystine. This supports the author's hypothesis on keratin decomposition by dermatophytes. According to this hypothesis, the fungus excretes sulfite which cleaves the disulfide bonds of keratin to cysteine and S-sulfocysteine. The substrate, denatured by sulfitolysis, is then more easily digestible by fungal proteases. Besides S-sulfocysteine, comparable amounts of cysteic acid were found in all analyses. This compound most probably originated by air oxidation of sulfur amino acids in the alkaline cultivation fluid.

Biodegradation, Environmental↗
PubMed1989

L-[35S]cysteic acid selectively detects chloride-dependent L-glutamate transporters in synaptic membrane.

Na+-independent L-[35S]cysteic acid (CA) accumulation in rat cortical synaptic membrane was examined. In the absence of Cl-, the accumulation was not observed. Addition of Cl- revealed the accumulation in a dose-dependent manner. Br- and NO3- also did. Ca2+-enhanced the Cl- -dependent accumulation, whereas low concentrations of Na+ reduced it. L-[35S]CA accumulation was inhibited by quisqualate, L-glutamate (L-Glu), L-cysteine sulfinate, D,L-homocysteic acid and D,L-2-amino-4-phosphonobutyrate (D,L-APB) potently. L-CA inhibited L-[3H]Glu accumulation in synaptic membrane in the presence of Cl-. The maximal inhibition of L-CA was equal to that of D,L-APB, but L-CA did not inhibit L-[3H]Glu accumulation in the absence of Cl-. These results show that L-[35S]CA selectively detects the Cl- -dependent L-Glu transporters in synaptic membrane.

Amino Acids, Sulfur↗
PubMed1990

Relaxed specificity of endoproteinase Asp-N: this enzyme cleaves at peptide bonds N-terminal to glutamate as well as aspartate and cysteic acid residues.

Asp-N, an endoproteinase specific for cleavage of protein or polypeptide bonds N-terminal to aspartate or cysteic acid residues, has been shown to possess a similar affinity for certain glutamate residues. Of 18 glutamate residues present in 2 cyanogen bromide fragments of apolipoprotein A-I, 5 residues were cleaved at rates comparable to that of cleavage at the 12 internal aspartate residues present in these polypeptides (all of which were cleaved). Cleavage of these 5 glutamate residues was obtained under standard enzyme digestion conditions, and the identities of all peptides obtained by Asp-N digestion were determined by amino acid sequencing of peaks obtained from reversed-phase high performance liquid chromatography.

Amino Acid Sequence↗
PubMed2004

Trichothiodystrophy: quantification of cysteine in human hair and nails by application of sodium azide-dependent oxidation to cysteic acid.

The term "trichothiodystrophy" (TTD) covers several autosomal recessive diseases whose diagnostic hallmark is short, brittle hair low in sulfur and cystine because of impaired synthesis of high-sulfur matrix protein. Clinical symptoms associated with TTD represent a variable range of abnormalities in organs derived from ectoderm and neuroectoderm. Important laboratory tests of the hair for the diagnosis of TTD comprise polarizing microscopy ("tiger-tail" pattern), electron microscopy, and amino acids analysis of hydrolyzed hair with a special focus on cystine. However, only very few institutions determine the amino acid composition of human hair and nail clippings, which requires special sample preparation including hydrolysis. If no special precautions are taken, quantification of cysteine and cystine becomes inaccurate because of decomposition of these residues during hydrolysis. We therefore performed the sample work-up with azide-dependent oxidation which we have for the first time adapted for analysis of hair and nail clippings. With our control and parent data resembling published data on hair and nail samples, we obtained a decreased proportion of cysteine (half cystine, determined as cysteic acid) in materials obtained from a boy with TTD. Clearly, the method for the quantification of cysteine following sodium azide-dependent oxidation is a suitable and rather convenient approach to the quantification of cyst(e)ine and other amino acids in hair and nail proteins, and is a valuable contribution to the diagnosis of TTD.

Cysteic Acid↗