dd‐Carboxypeptidase Activity of Membrane Fragments of Mycobacterium smegmatis

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Abstract
A DD-carboxypeptidase [EC 3.4.12.6] activity is present in membrane fragments of M. smegmatis. Kinetic parameters of the enzymatic activity were studied using UDP-N-glycolylmuramyl-L-alanyl-.gamma.-D-glutamyl-meso-2,2''-diaminopimelyl-D-[14C]alanyl-D-[14C]alanine as substrate. The DD-carboxypeptidase can be solubilized by Triton X-100 and Genapol X-100. It is inhibited by .beta.-lactam antibiotics although intact cells of M. smegmatis are insensitive to that kind of antibiotics. Inhibition by penicillin G is slowly reversible. By storage, at -20.degree. C, kinetic parameters and sensitivity to penicillin G vary non-concomitantly, suggesting a penicillin binding site different from the substrate binding site.