L-cysteic acid

Sanchez-Cano et al. have proposed paired synthesis for obtaining L-cysteic acid and L-cysteine from L-cystine which greatly improves the economical parameters [57], The global process-flow for the paired synthesis, with L-cystine and water as starting materials is shown in Fig. 3. Table 2 compares the results for the paired (B) and the individual syntheses (A, C). 

L-Cysteic acid residues were produced within the peptide chain when submaxillary-gland glycoprotein from sheep was treated with alkali (pH 9.0), during 24 hours at room temperature in the presence of sulfite (0.1 M). The yield was —55% on the basis of the L-serine decomposed, and the corresponding derivative from L-threonine was not detected.167... 

L-Cysteic acid Oxidation product of 1,-Cysteine mGlu-R Class I (la, 5a) agonist... 

L-Aspartic Acid L-Cysteic Acid L-Cysteine Sulphinic Acid L-Glutamic Acid... 

Rosowski, A., Eorsch, R. A., Freisheim, J. H., Moran, R. G., Wick, M. Methotrexate analogues. 19. Replacement of the glutamate side chain in classical antifolates by L-homocysteic acid and L-cysteic acid effect on enzyme inhibition and antitumor activity. J. Med. Chem. 1984,27, 600-604. 

Studies on the inhibition of partially purified FPGS from human liver by the sulphonic acid analogues of MTX and AMT have also been reported [288]. The L-homocysteic acid analogues L-(VIII.IOO) and l-(VIII.102) had estimated K, values of 131 5 and 35 2 /iM, respectively, whereas the corresponding values for the L-cysteic acid analogues L-(VIII.lOl) and l-(VIII.103) were 173 + 6 and 66 5 pM. Interestingly, the kinetics of inhibition observed with the human enzyme were strictly competitive for l-(VIII. 100) and l-(VIII.102), but were of the mixed type for L-(VIII.lOl) and l-(VIII.103). While the latter... 

Enzymatic decarboxylation169 of L-cysteic acid-35S (equation 86) by the tissues of chicken embryo has been investigated by Fromageot and coworkers170. Enzyme preparations from liver appeared to be the most active, and the authors determined [35S]taurine as well as unreacted 35S-cysteic acid, 35S-/Lsulphonylpyruvic acid and 35S-sulphate. The reaction is inhibited by L-cysteine sulphinic acid, by DL-a-methylcysteic acid, CH2ICOONa, NaCN and by hydroxylamine. The enzyme is activated by pyridoxal phosphate. 

I, D-lysine 2, L-lysine 3, D-arginine 4, glycine 5, D-alanine, D-serine 6, D-threonine 7, D-arginine 8, L-threonine, L-alanine, D-hi tidine 9, D-cysteic acid 10, L-cysteic acid ... 

Literature proposed CZE methods for phenols and derivatives using test mixtures based on aqueous buffered systems (phosphate-borate and borate " ), volatile electrolytes (ammonium hydrogencarbonate, diethylmalonic acid/dimethylamine in isopropanol and L-cysteic acid, 3-amino-1-propanesulfonic acid, aminomethanesulfonic acid, and diethylmalonic acid ), andnon-aqueous media (ammonium acetate in ACN/acetic acid in MeOH acetate, bromide, chloride, and malonate in ACN and diprotic acids/tetrabutylammonium hydroxide and maleate in MeOH ). 

The exchange of labelled sulphur can be promoted by enzyme catalysts, instead of heating. Bird egg yolk and the cysteine desulphydrase that it contains catalyse the exchange of sulphur-35 from Na2 S to L-cysteine, L-cystine and L-cysteic acid. In a typical experiment, 150 ml of a buffer solution containing 2 millimoles of cysteine-HCl, 2 millimoles of Naa S and 500 mg of cysteine desulphydrase preparation is incubated at 38°C for 15 h. A mixture of 74-4% cystine- S and 25-3% cysteine- S is obtained. L-Cystine- S is subsequently reduced electrolytically to cysteine- S. The total yield of L-cysteine- S obtained by isotope exchange is 70%. 

Sulfinic acids, e.g., L-cysteine sulfinic acid and hypotaurine, and sulfonic acids, e.g., L-cysteic acid and taurine, are naturally occurring products of L-cysteiiie and cysteamine oxygenation. They occur in microorganisms, plants, and animals. 

L-Cysteine is transformed to L-cysteine sulfinic acid and L-cysteic acid. Cysteamine (D 11) yields hypotaurine and taurine (Fig. 189). The latter compounds may be transformed to other secondary products by deamination, thiolation, guanylation, and methylation. L-Cysteine sulfinic acid may be degraded to L-alanine and sulfurous acid, which is oxidized to sulfuric acid. 

Other amino-acids which have been studied include L-cysteic acid mono-hydrate,which is conformationally similar to L-cysteine and taurine, and (—)-2-aA o-amino-norbornane-2-carboxyllc acid hydrobromide which has been shown to have the absolute configuration (li , 2R, AS). DL-Tryptophan formate exhibits an anti conformation about the C -Cp bond, in contrast to the gauche arrangement observed in the hydrochloride. 

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