Purification and Properties of {beta}-Lactamases from Serratia marcescens

1 Department of Microbiology, School of Medicine, Gunma University, Maebashi, Gunma 371, Japan 2 Laboratory of Drug Resistance in Bacteria, School of Medicine, Gunma University, Maebashi, Gunma 371, Japan 3 Central Research Laboratories, Sankyo Co. Ltd, Shinagawa-ku, Tokyo 140, Japan ABSTRACT Both a penicillinase and a cephalosporinase were purified from a strain of Serratia marcescens (GN7647) resistant to β-lactam antibiotics. The penicillinase was identical to the type I penicillinase, mediated by Rms212 and R-TEM. The purified cephalosporinase, a typical chromosomally mediated enterobacterial β-lactamase, gave a single protein band on polyacrylamide gel electrophoresis and immunoelectrophoresis; the pI was 9·56 and its molecular weight was approximately 37000. It contained tryptophan but not cysteine. The specific activity was 374 units (mg protein) -1 for the hydrolysis of cephaloridine, and the optimal pH was 8·5. Rabbit antisera raised against the purified cephalosporinase showed no cross-reaction in a neutralization test with cephalosporinases produced by other species of Enterobacteriaceae . Present address: Central Research Laboratories, Sankyo Co. Ltd, 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140, Japan.