Do intermolecular association phenomena occur in B. cereus beta-lactamase I?

Although at fixed enzyme concentration the hydrolysis of cephaloridine by B. cereus beta-lactamase I followed apparently classical Michaelis-Menten steady-state kinetics, the values of kcat and of Km depended linearly, in the absence of added non-enzymatic proteins, on the absolute enzyme concentration. In the presence of gelatin, this dependence was abolished; under these conditions, however, the pseudo-first order kinetic rate constants of inactivation by Zn2+ ions exhibited a direct dependence on enzyme concentration and an inverse one on Zn2+ ions concentration. These results can be interpreted as indicating that intermolecular association phenomena play a role in determining the catalytic properties of the enzyme.