Purification and properties of a new beta-lactamase from Pseudomonas cepacia

An inducible beta-lactamase was purified from a beta-lactam antibiotic-resistant strain (GN11164) of Pseudomonas cepacia. The purified enzyme preparation gave a single protein band on polyacrylamide gel electrophoresis. The specific enzyme activity for the hydrolysis of cephalothin as a substrate was 314.5 U/mg of protein. The optimal pH was about 8.0, and the optimal temperature was 45 degrees C. The isoelectric point was 9.3, and the molecular weight was estimated to be about 22,000 to 24,000 from gel filtration on a Sephadex G-200 column and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme activity was inhibited by iodine, p-chloromercuribenzoate, clavulanic acid, CP 45899, and cloxacillin. The beta-lactamase showed a unique substrate profile by hydrolyzing most of the cephalosporins, including cefuroxime, cefotaxime (HR 756), ampicillin, and penicillin G, at a high rate.