Abstract
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 .times. 106-75 .times. 106 M-1 .cntdot. S-1]. The kcat values for ampicillin. were 1.0-100-fold lower. Carbenicillin, oxacillin, cloxacillin and methicillin were very poor substrates, exhibiting kcat values between 1 .times. 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.