The purification and properties of a penicillinase whose synthesis is mediated by an R-factor in Escherichia coli

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Abstract
The penicillinase ([beta]-lactamase) from E. coli strain-TEM has been purified and its activity against a range of penicillin and cephalosporin derivatives measured. The enzyme shows little resemblance to penicillinases from Bacillus cereus, B. licheniformis and Staphylococcus aureus. The molecular weight of the enzyme is 16700 [plus or minus] 5%, which is about half the value obtained for other penicillinases. The enzyme is most similar in properties to a crude preparation of a penicillinase from Klebsiella (Aerobacter) aerogenes, but clearly different from crude enzyme preparations from other strains of E. coli. Since penicillinase synthesis in E. coli strain TEM is mediated by an R-factor known to infect many other species of Enterobacteriaceae, the appearance of similar enzymes in other gram-negative species is not surprising.