Interaction of beta-lactamase of Streptomyces cacaoi. II. CP-45,899, izumenolide and cephamycins.

Inhibition of a beta-lactamase of Streptomyces cacaoi by CP-45,899, izumenolide and cephamycins was investigated and compared with that of a beta-lactamase of Bacillus cereus. S. cacaoi enzyme could not hydrolyze CP-45,899. Instead, hydrolysis of benzylpenicillin by the enzyme was inhibited in the presence of CP-45,899. Although inhibition increased gradually with time, the inhibition line produced by CP-45,899 with time less curved than that produced by clavulanic acid and PS-5. Furthermore, preincubation of S. cacaoi beta-lactamase with CP-45,899 for up to 120 seconds did not obviously affect the degree of inhibition. When the concentration was lowered, it behaved as a competitive inhibitor, a Ki value being 6.2 X 10(-7) M. Izumenolide, on the other hand, did not inhibit the enzyme activity of S. cacaoi beta-lactamase at 1.28 X 10(-4) M, although it inhibited B. cereus enzyme slightly in a competitive manner. Oganomycins were inert to the both beta-lactamases.U