Penicillin-sensitive transpeptidation during peptidoglycan biosynthesis in cell-free preparations from Bacillus megaterium. I. Incorporation of free diaminopimelic acid into peptidoglycan.

The effect of penicillins and cephalosporins on the various transpeptidation reactions presented in the preceding paper is discussed. Inhibition by cloxacillin and penicillin G of [Wldiaminopimelic acid incorporation during peptidoglycan synthesis appeared to be partially reversible after the antibiotic was destroyed by treatment with penicillinase. Inhibition of the cross-linking reaction by cloxacillin appeared to be fully reversible. These and other results suggested the presence of more than one transpeptidase. In addition, a D-alanine carboxypeptidase activity present in the particulate enzyme preparation was examined and found to be irreversibly inhibited by penicillin G and relatively insensitive to cloxacillin. It is suggested that the transpeptidases(s) and the D-alanine carboxypeptidase are separate enzymes.