PubMed Health⌕ Search

Biomedical subjects

S Duprè

Publications and source records attributed to S Duprè.

11 recordsLinked to original sources
PubMed1992

Enzymatic synthesis of S-aminoethyl-L-cysteine from pantetheine.

The recently characterized compound S-aminoethylcysteine ketimine can be synthesized from purified S-aminoethylcysteine by enzymatic systems (transaminases or L-amino acid oxidase) present in mammalian tissues. S-Aminoethylcysteine, which could be considered as the natural precursor of the ketimine, is produced from L-serine and cysteamine by the action of the enzyme cystathionine-beta-synthase. We demonstrate in this paper that pantetheine, a normal cellular component, is an efficient cysteamine donor for the synthesis of S-aminoethylcysteine and of S-aminoethylcysteine ketimine in the place of free cysteamine, and we describe the enzymatic system, composed of partially purified enzymes, for the in vitro synthesis of S-aminoethylcysteine ketimine from pantetheine. This seems to indicate a new biological role for pantetheine.

Amidohydrolases↗
PubMed1991

Sulfur-containing cyclic ketimines and imino acids. A novel family of endogenous products in the search for a role.

Aminoethylcysteine, lanthionine, cystathionine and cystine are mono-deaminated either by L-amino-acid oxidase or by a transaminase exhibiting the properties described for glutamine transaminase. The deaminated products cyclize producing the respective ketimines. Authentic samples of each ketimine were prepared by reacting the appropriate aminothiol compound with bromopyruvate, except cystine ketimine which required the interaction of thiopyruvate with cystine sulfoxide. Reduction of the first three mentioned ketimines with NaBH4 yields the respective derivatives with the saturated rings of thiomorpholine and hexahydrothiazepine. The same reduction is carried out enzymically by a reductase extracted from mammalian tissues. Properties of the members of this family of compounds are described. Gas chromatography followed by mass spectrometry permits the identification of most of these products. HPLC is very useful for the determination of the ketimines by taking advantage of specific absorbance at 380 nm obtained by prior derivatization with phenylisothiocyanate. Adaptation of these and other analytical procedures to biological samples disclosed the presence of most of these compounds in bovine brain and in human urine. By using [35S]lanthionine ketimine as a representative member of the ketimine group, the specific, high-affinity, saturable and reversible binding to bovine brain membranes has been demonstrated. The binding is removed by aminoethylcysteine ketimine and by cystathionine ketimine indicating the occurrence in bovine brain of a common binding site for ketimines. The reduced ketimines are totally ineffective in competing with [35S]lanthionine ketimine. Alltogether these findings are highly indicative for the existence in mammals of a novel class of endogenous sulfur-containing cyclic products provided with a possible neurochemical function to be investigated further.

Amino Acids, Sulfur↗
PubMed1977

Is the alkaline cleavage of disulfide bonds in peptides an alpha-beta elimination reaction or a hydrolysis?

The cleavage of oxidized glutathione by alkali has been studied as representative of the cleavage of protein disulfides. This process is quite different when studied in 10-4N or 2-10-1N NaOH. At low alkali concentration no spectral changes are noted; at higher hydroxyl concentration the appearance of persulfide groups (followed at 335 nm), the formation of thiocyanate (arising from cold cyanolysis of persulfide groups) and the absorbance at 240 nm follow the same kinetics. The amount of half-cystine, recovered as cysteic acid after a 3-h reaction, is significantly lower than calculated. These results confirm that oxidized glutathione undergoes beta-elimination at high pH values, and that persulfide groups absorb not only at 335 nm (as already known) but also at 240 nm where, under our conditions, the contribution of other absorbing species is not very high.

Alkalies↗
PubMed1975

Hydroxyamino compounds produced by the oxidation of diamines with diamine oxidase in the presence of alcohol dehydrogenase.

When the diamines putrescine, cadaverine, cystamine and lanthionamine are oxidized by purified pig kidney diamine oxidase in the presence of NADH and either liver or yeast crystalline alcohol dehydrogenase, NADH is oxidized. Chromatographic evidence obtained in the case of putrescine and cystamine indicates the production of the respective hydroxy-amino compound. In the case of cystamine, the product of the reaction is mercapto-ethanol-cysteamine mixed disulfide which may represent a biological source for the production of mercaptoethanol used for other reactions.

Alcohol Oxidoreductases↗
PubMedDate not supplied

In vitro enzymatic conversion of pantothenylcysteine-4'-phosphate into cysteamine.

In vivo production of taurine can not proceed from cysteine via the action of cysteinsulphinic acid-decarboxylase in those mammalian organs where this enzymatic activity is absent, such as heart. The possibility of existence of another metabolic way is strengthened by the experimental finding that, in vitro, cysteamine is obtained from pantothenylcysteine-4'-phosphate through the combined action of two mammalian enzymes, i.e. pantothenylcysteine-4'-phosphate decarboxylase and pantetheinase, used in partially purified forms. This new route should be related to the known biosynthetic pathway of CoA.

Acid Phosphatase↗