A survey of the kinetic parameters of class C beta-lactamases. Penicillins.
The interaction between six class C beta-lactamases and various penicillins has been studied. All the enzymes behaved in a very uniform manner. Benzylpenicillin exhibited relatively low kcat. values (14-75 s-1) but low values of Km resulted in high catalytic efficiencies [kcat./Km = 10 X 10(6)-75 X 10(6) M-1.s-1]. The kcat. values for ampicillin were 10-100-fold lower. Carbenicillin, oxacillin cloxacillin and methicillin were very poor substrates, exhibiting kcat. values between 1 x 10(-3) and 0.1 s-1. The Km values were correspondingly small. It could safely be hypothesized that, with all the tested substrates, deacylation was rate-limiting, resulting in acyl-enzyme accumulation.
Galleni
M
M
Laboratoire d'Enzymologie, Université de Liège, Sart Tilman, Belgium.
Frère
J M
JM
D000667:Ampicillin / Q000378:metabolism; D002228:Carbenicillin / Q000378:metabolism; D003023:Cloxacillin / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D008712:Methicillin / Q000378:metabolism; D010068:Oxacillin / Q000378:metabolism; D010400:Penicillin G / Q000378:metabolism; D010406:Penicillins / Q000378:metabolism*; D013379:Substrate Specificity; D001618:beta-Lactamases / Q000378:metabolism*
D007527:Isoenzymes; D010406:Penicillins; D000667:Ampicillin; D001618:beta-Lactamases; D002228:Carbenicillin; D003023:Cloxacillin; D010400:Penicillin G; D008712:Methicillin; D010068:Oxacillin