Interaction between Penicillin and the dd‐Carboxypeptidase of the Unstable l‐Form of Proteus mirabilis, Strain 19

Abstract

Binding of penicillin to the dd‐carboxypeptidase of the unstable spheroplast L‐form of Proteus mirabilis results in the rapid formation of a modified enzyme‐inhibitor complex which in turn under goes rapid decay into reactivated enzyme and an antibiotically inactive penicillin degradation product. Major antibiotic metabolites recovered from such interactions were benzylpenicilloic acid and phenoxymethylpenicilloic acid from benzylpencillin and phenoxymethylpenicillin, respectively, suggesting a second enzymic function of the dd‐carboxypeptidase as a penicillinase of low efficiency. Statistical analyses made with the help of a linear regression program show that the enzyme interacts with the substrate UDP‐N‐acetylmuramoyl‐l‐alanyl‐d‐γ‐glutamyl‐(l)‐meso‐2,6‐diaminopimelyl‐(l)‐d‐alanyl‐d‐alanine and either benzylpencillin or carbenicillin in a non‐competitive manner. Copyright © 1978, Wiley Blackwell. All rights reserved