C. De Marco

Oxidative deamination of D-homocysteinesulfinic acid.

Homocysteinesulfinic acid (HCS) has been prepared by Jolles-Bergeret [l] , who also demonstrated that it is deaminated by liver glutamate dehydrogenase (L-glutamate:NAD(P) oxidoreductase, deaminating EC 1.4.1.3) with production of ammonia and an ol-ketosulfinic acid [2] , and is decarboxylated by a crude preparation of glutamate decarboxylase from Clostridium welchii with production of homohypotaurine [3] , These results confirm the suggestion that, because of the great similarity in structure of glutamic acid and HCS in the latter S02H replaces a carboxyl group these compounds may be good substrates for the same enzyme. Jolles-Bergeret further reports [2] that D-homocysteinesulfinic acid is not oxidized by hog kidney D-aminoacid oxidase (D-amino acid: oxygen oxidoreductase, deaminating EC 1.4.3.3). This results may be an obvious consequence of the fact that dicarboxylic amino acids are not affected by D-amino acid oxidase, but are substrates for the D-aspartate oxidase (D-aspartate:oxygen oxidoreductase, deaminating EC 1.4.3 .l) [4-71 . We have therefore investigated the oxidative deamination of D-HCS by D-aspartate oxidase, to have further indications that enzymes active on glutamate also may be active on HCS. It may be emphasized that D-aspartate oxidase is active on D-cysteinesulfinic acid [8] , which shows the same analogy with aspartic acid that HCS shows with glutamic acid.

Oxidation of Se-Carboxymethyl-selenocysteine by L-aminoacid oxidase and by D-aspartate oxidase

SummarySe-Carboxymethyl-DL-selenocysteine (CMSeC) has been prepared in a pure crystalline form from selenocysteine and monochloroacetic acid. It has been shown that CMSeC is a substrate for the L-aminoacid oxidase from snake venom and for the D-aspartate oxidase from beef kidney. Oxygen consumption and ammonia production indicate that only the L or the D form of CMSeC are acted upon respectively by one or the other of the above enzymes. No noticeable differences were shown in the oxidation rate of CMSeC and S-carboxymethylcysteine, an indication that the substitution of a selenium for a sulfur atom in the molecule does not greatly affect the substrate specificity of the two enzymes. Data have been obtained suggesting that the product of the oxidative deamination of CMSeC is Se-carboxymethyl-selenopyruvic acid.

Identification of S-carboxymethyl-thiopyruvate as the product of oxidative deamination of S-carboxymethyl-cysteine

SummaryBromopyruvic acid and thioglycolic acid react to form carboxymethylthiopyruvic acid, which was then isolated as the 2,4-dinitrophenylhydrazone. Chromatographic and spectral properties of the compound have been investigated. Using this as a reference standard, it has been possible to demonstrate that carboxymethylthiopyruvate is the main product of the oxidative deamination of carboxymethylcysteine, D-isomer, catalyzed by D-aspartate oxidase. It has been demonstrated moreover that carboxymethylcysteine, L-isomer, may be a substrate for snake venom L-aminoacid oxidase.

Pyridoxal phosphate-catalyzed α-β elimination of lanthionine and cystathionine

Abstract In sodium phosphate buffer pH 8.5, at 38 °, pyridoxal-5-phosphate catalyzes α-β elimination reactions on lanthionine and cystathionine, with production of ammonia, pyruvate, and cysteine, or homocysteine, respectively. In the same experimental conditions pyridoxal-phosphate cannot catalyze α-γ elimination on cystathionine or on S-β-amino-ethylhomocysteine.

Chromatographic separation of selenohypotaurine, selenotaurine, selenohomohypotaurine and selenohomotaurine

By either paper or ion-exchange chromatography the two seleninic compounds selenohypotaurine and selenohomohypotaurine, and the two selenonic compounds selenotaurine and selenohomotaurine may be all separated from each other. On paper chromatography seleninic derivatives may be separated from the corresponding sulphinic compounds, while selenonic compounds show RF values similar to those of the corresponding sulphonic derivatives. These two latter types of compounds may be differentiated, however, since selenonic compounds liberate iodine from HI, while sulphonic compounds do not. Also by automated ion-exchange chromatography seleninic derivatives are well separated from the analogous sulphinic compounds, while selenonic compounds are eluted together with the corresponding sulphonic compounds.

SYNTHESIS AND CHROMATOGRAPHIC PROPERTIES OF S-CARBOXYMETHYLHOMOCYSTEAMINE (2 CARBOXYMETHYL-3-AMINOPROPYL SULFIDE)

Abstract Details are reported for the synthesis of carboxymethylhomocysteamine starting either from homocysteamine and monochloroacetic acid, or from 3-brompropylamine and thioglycolic acid. CMHC was obtained in pure crystalline form, and with fairly good yield. The corresponding sulfoxide and sulfone have also been prepared in a crystalline form. These compounds may be separated by paper chromatography, and identified by specific reactions. On the Amino Acid Analyzer they may be easily separated from each other and from the homologous carboxymethylcysteamine, its sulfoxide and its sulfone, using the long column and the standard sodium citrate buffers at pH 3.25 and 4.25.