Production and Property of Beta-lactamases in Streptomyces

The production of beta-lactamases by 100 strains of Streptomyces was studied. About one-half of the strains produced more than 2.3 U of beta-lactamase per ml, and another half produced less than 1.4 U/ml. The amounts of beta-lactamases produced by two strains were in the order of those produced by Bacillus cereus 569/H and Bacillus licheniformis 749/C. These Streptomyces enzymes function primarily as penicillinases rather than cephalosporinases. Properties such as pH optimum, substrate specificity, and heat stability suggest that these Streptomyces beta-lactamases are closely related to each other. In contrast to bacterial beta-lactamases, Streptomyces beta-lactamases were insusceptible to inactivation by N-bromosuccinimide and only slightly susceptible to iodine. This suggests that the construction mode of the active site would be different from other beta-lactamases. Studies on the minimum inhibitory concentrations of benzylpenicillin to seven Streptomyces strains and on their maximum beta-lactamase production indicate that the susceptibility of Streptomyces to penicillin is not directly related to the beta-lactamase production.