Purification and properties of a chromosomal .BETA.-lactamase from Klebsiella oxytoca.

A β-lactamase was purified from Klebsiella oxytoca strain GN10650. The enzyme was chromosomally-mediated and gave a single protein band on polyacrylamide gel electrophoresis. Its pI was 5.34 and its MW was approximately 27, 000. The optimal pH and temperature were about 7.0 and 50°C, respectively. The specific activity of the enzyme was 1, 207 units per mg of protein for hydrolysis of penicillins and cephalosporins, including cefuroxime, cefotaxime, and aztreonam. The enzyme activity was inhibited by p-chloromercuribenzoate, iodine, ferrous ion, and by clavulanic acid. Rabbit antibodies raised against the purified K. oxytoca enzyme showed no cross-reactivity in neutralization tests with β-lactamases produced by other species of Gram-negative bacteria.