The inactivation of beta-lactamase I from B. Cereus by dicloxacillin: effect of buffer composition on the kinetic characteristics of the modified enzyme.

Buffer composition affects the pattern of inactivation of B. cereus beta-lactamase I by dicloxacillin. At pH 7.0, in the presence of phosphate ions, dicloxacillin appears to cause essentially an irreversible inactivation of the catalytic site of the enzyme, while in a tris-cacodylate buffer the inactivation process appears to affect essentially the substrate-binding site. Buffer ions act presumably by interacting themselves with either the catalytic or the substrate-binding site of the enzyme, thus modifying the affinity of these sites for the halogenated isoxazolyl-penicillins.