Positively cooperative binding of zinc ions to Bacillus cereus 569/H/9 beta-lactamase II suggests that the binuclear enzyme is the only relevant form for catalysis.

Metallo-beta-lactamases catalyze the hydrolysis of most beta-lactam antibiotics and hence represent a major clinical concern. While enzymes belonging to subclass B1 have been shown to display maximum activity as dizinc species, the actual metal-to-protein stoichiometry and the affinity for zinc are not clear. We have further investigated the process of metal binding to the beta-lactamase II from Bacillus cereus 569/H/9 (known as BcII).

Inactivators in competition. How to deal with them ... and not!

A method is described to determine the values of the equilibrium (K) and rate (k(2)) constants for enzyme inactivations which occur according to two-step pathways involving a first non-covalent complex and a covalent, irreversibly inactivated adduct. The method rests on a competition between a reference compound [R] for which the k(2) and K values are already known and another inactivator [C]. During the experiments, the disappearance of the reference compound or the appearance of the ER(*) adduct is monitored.