Characterization of the -lactamase specified by the resistance factor R-1818 in E. coli K12 and other Gram-negative bacteria.

1. The amino acid composition of the beta-lactamase from E. coli (R-1818) was determined. 2. The R-1818 beta-lactamase is inhibited by formaldehyde, hydroxylamine, sodium azide, iodoacetamide, iodine and sodium chloride. 3. The K(m) values for benzylpenicillin, ampicillin and oxacillin have been determined by using the R-factor enzyme from different host species. The same values were obtained, irrespective of the host bacterium. 4. The molecular weight of the enzyme was found to be 44600, and was the same for all host species. 5. The relationship of R-1818 and R-GN238 beta-lactamases is discussed.