title: Purification and properties of chromosomally mediated beta-lactamase from Citrobacter freundii GN7391.
abstract: Both a penicillinase and a cephalosporinase are present in a strain of Citrobacter freundii (GN7391) resistant to beta-lactam antibiotics. The penicillinase was identical to the type Ia penicillinases (Type III by Richmond classification), mediated by Rms212 and R-TEM. A cephalosporinase, typical of enterobacteriaceae chromosomal beta-lactamase (Type I by Richmond classification), was purified from the strain. It gave a single protein band on polyacrylamide gel electrophoresis and immunoelectrophoresis; the pI was 8.6 and its molecular weight was approximately 38 000. Cysteine was not found among its amino acids. The specific activity was 388 units (mg protein)-1 for the hydrolysis of cephaloridine, and the optimal pH was 8.0. Rabbit antiserum obtained against the purified enzyme showed cross-reaction with cephalosporinases produced by strains of Enterobacter cloacae in a neutralization test.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002510:Cephalosporinase / Q000302:isolation & purification; D002954:Citrobacter / Q000187:drug effects / Q000201:enzymology*; D008826:Microbial Sensitivity Tests; D009500:Neutralization Tests; D010405:Penicillinase / Q000302:isolation & purification; D001618:beta-Lactamases / Q000302:isolation & purification*
chemical_list: D000596:Amino Acids; D000900:Anti-Bacterial Agents; D002510:Cephalosporinase; D010405:Penicillinase; D001618:beta-Lactamases