Interaction of .BETA.-lactamase of Streptomyces cacaoi. II. Cp-45,899, Izumenolide and cephamycins.

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Abstract
Inhibition of a .beta.-lactamase of S. 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. 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 was less curved than that produced by clavulanic acid and PS-5. Preincubation of S. cacaoi .beta.-lactamase with CP-45,899 for up to 120 s 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 .times. 10-7 M. Izumenolide did not inhibit the enzyme activity of S. cacaoi .beta.-lactamase at 1.28 .times. 10-4 M, although it inhibited B. cereus enzyme slightly in a competitive manner. Oganomycins were inert to both .beta.-lactamases.