Kinetics of interaction between the exocellular DD-carboxypeptidase-transpeptidase from Streptomyces R61 and beta-lactam antibiotics. A choice of models.
The simplest model for the interaction between the exocellular DD-carboxypeptidase-transpeptidase from Streptomyces R61 and beta-lactam antibiotics involves the three following steps: (a) the formation of a reversible equimolar enzyme - antibiotic complex; (b) the irreversible transformation of this complex into a modified enzyme - antibiotic complex; and (c) the breakdown of this latter complex and the concomitant release of a regenerated enzyme and a modified antibiotic molecule. The dissociation constant for step 1 and the rate constants for steps 2 and 3 were measured with various beta-lactam antibiotics. With antibiotic such as benzylpenicillin, which behaves as a good 'substrate', steps 1 and 2 occur at enzymic velocities, whereas step 3 occurs at a very low velocity and hence is responsible for the low efficiency of the overall process.
D000217:Acyltransferases / Q000378:metabolism*; D000667:Ampicillin / Q000378:metabolism; D001665:Binding Sites; D002228:Carbenicillin / Q000378:metabolism; D002268:Carboxypeptidases / Q000378:metabolism*; D007700:Kinetics; D008433:Mathematics; D010400:Penicillin G / Q000378:metabolism; D010406:Penicillins / Q000378:metabolism*; D010458:Peptidyl Transferases / Q000378:metabolism*; D011485:Protein Binding; D013302:Streptomyces / Q000201:enzymology*
D010406:Penicillins; D000667:Ampicillin; D000217:Acyltransferases; D010458:Peptidyl Transferases; D002268:Carboxypeptidases; D002228:Carbenicillin; D010400:Penicillin G