Exocellular β-Lactamases of Streptomyces albus G and Strains R39 and K11

摘要

The β-lactamases excreted by the highly benzylpenicillin-susceptible Streptomyces strain R39 and the highly benzylpenicillin-resistant Streptomyces albus G were isolated and purified. Neither β-lactamase exhibited dd-carboxypeptidase activity. Both were anionic at pH 8.3, did not require metal ions, and were not sensitive to iodine, but were inhibited by Cu²⁺ and readily inactivated by heat. p-Chloromercuribenzoate, iodoacetate, p-aminobenzoate, and substrates and inhibitors of dd-carboxypeptidase had no effect on β-lactamase activity. The Km and Vmax values for β-lactamase activity were studied with 6-aminopenicillanic acid and with various penicillins and cephalosporins. The β-lactamase from the related strain K11 of Streptomyces, which is intermediate in its susceptibility to benzylpenicillin, was partially purified, and its activity was compared on the various substrates.