Purification and Properties of Chromosomally Mediated Beta-Lactamase From Citrobacter Freundii GN7391

J Gen Microbiol. 1980 Dec;121(2):449-56. doi: 10.1099/00221287-121-2-449.


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

  • Amino Acids / analysis
  • Anti-Bacterial Agents / pharmacology
  • Cephalosporinase / isolation & purification
  • Citrobacter / drug effects
  • Citrobacter / enzymology*
  • Microbial Sensitivity Tests
  • Neutralization Tests
  • Penicillinase / isolation & purification
  • beta-Lactamases / isolation & purification*


  • Amino Acids
  • Anti-Bacterial Agents
  • Cephalosporinase
  • Penicillinase
  • beta-Lactamases