Purification and properties of a beta-lactamase from Alcaligenes dentrificans subsp. xylosoxydans

A penicillin beta-lactamase was purified from a strain of Alcaligenes dentrificans subsp. xylosoxydans resistant to beta-lactam antibiotics. The purified enzyme preparation gave a single protein band on polyacrylamide gel electrophoresis, and its molecular weight was 18,000 from sodium dodecylsulphate-acrylamide gel electrophoresis and gel filtration. Its isoelectric point was 9.8, the optimal pH was 8.5 and the optimal temperature was 35 degrees C. The enzyme hydrolyzed penicillin G and ampicillin more rapidly than cephalosporins. Relative rates, with penicillin G as 100, were: ampicillin, 102; carbenicillin, 15; cloxacillin, less than 1; piperacillin, 9; cephaloridine, 41; cefoperazone, 36; cefpiramide, 36 and cefmenoxime, 14. Clavulanic acid, sulbactam, imipenem, and cephamycins had low affinities for the enzyme. The enzyme activity was inhibited by iodine, Hg2+, clavulanic acid and sulbactam.