Specificity Profiles of the Membrane‐Bound γ‐d‐Glutamyl‐(l)meso‐diaminopimelate Endopeptidase and ld‐Carboxypeptidase from Bacillus sphaericus 9602

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Abstract
Membrane‐bound peptidases from Bacillus sphaericus 9602 were tested upon various peptides in order to determine the substrate requirements of each enzyme. Ld‐Carboxypeptidase and γ‐d‐glutamyl‐meso‐diaminopimelate endopeptidase were never both found to be active on the same substrate. Ld‐Carboxypeptidase splits the l‐Lys‐d‐Ala linkage of lysine‐containing substrates and the msA2pm‐d‐Ala linkage of meso‐diaminopimelic‐acid‐containing substrates which have an amide group on the ω‐carboxyl. The endopeptidase hydrolyses the linkage of meso‐diaminopimelic‐acid‐containing peptides and derivatives with free ω‐NH2 and ω‐COOH groups. The presence or the absence of an α‐amide group on glutamic acid, the second residue of peptides, has no influence on the specificities of either enzyme. Likewise, N‐substitution of N‐terminal l‐alanine does not modify the enzymic specificities. Kinetic studies have shown that and are good substrates for Ld‐carboxypeptidase (apparent Km= 0.8 mM and 1.25 mM, respectively). is the best substrate for the endopeptidase (apparent Km= 0.33 mM). An amide group on glutamic acid gives a decrease of 80% of both Ld‐carboxypeptidase and endopeptidase activities. Various inhibitors of endopeptidase were studied:DD and meso‐diaminopimelic acid isomers are very good inhibitors. Dicarboxylic d‐amino acids also show an inhibition which is a function of the length of the side chain: the maximum is observed for n= 4 (d‐α‐aminopimelic acid).