titration of the active-site serine dd-peptidase of streptomyces r61 shows that formation of acyl enzyme during hydrolysis of the substrate ac2-l-lys-d-ala-d-ala and enzyme inactivation by the beta-lactam compounds benzylpenicillin , n-acetylampicillin and ampicillin relies on the acidic form of an enzyme 's group of pk approximately equal to 9.5 .
C0030827
benzylpenicillin
C0002680
ampicillin