Stereochemical Analysis of γ-Replacement and γ-Elimination Processes Catalyzed by a Pyridoxal Phosphate Dependent Enzyme

Article abstract of DOI:10.1021/ja00406a041

(Z)- and (E)-<4-2H>Vinylglycine samples have been synthesized and used to determine the stereochemical outcome of a pyridoxal phosphate dependent bacterial enzyme cyctathionine γ-synthase.For the first time both the γ-replacement mode, vinylglycine or O-succinylhomoserine to cystathionine, and the γ-elimination mode, vinylglycine or O-succinylhomoserine to α-ketobutyrate, have been solved stereochemically.The diastereomeric <4-2H>cyctathionines produces enzymically in the γ-replacement mode were degraded to <4-2H>homoserines, the absolute chiralities were determined, and then the compounds were succinilated.The O-succinyl<4-2H>homoserines were then processed enzymically to <4-2H>cystathionines enzymically, and the stereochemical course of the first half-reaction was thereby determined.