Streptomyces K15 DD-peptidasecatalysed reactions with ester and amide carbonyl donors

The values ofthe kinetic parameters that govern the interactions between the Streptomyces K15 DD-peptidase and,J-lactam compounds were determined by measuring the inactivating effect that these compounds exert on the transpeptidase activity of the enzyme and, in the case of [14C]benzylpenicillin and [14C]cefoxitin, by measuring the amounts of acyl-enzyme formed during the reaction. K15 DD-peptidase binds benzylpenicillin or cefoxitin at a molar ratio of 1: 1. Benzylpenicilloate is the major product released during breakdown of the acyl-enzyme formed with benzylpenicillin. Benzylpenicillin is not a better acylating agent than the amide AC2-L-Lys-D-Ala-D-AlaandesterAc2-L-Lys-D-Ala-D-lactatecarbonyl-donor substrates.,l-Lactamcompoundspossessing a methoxy group on the a-face of the molecule show high inactivating potency