Characterization of the membrane beta-lactamase in Bacillus cereus 569/H/9.
The membrane-bound beta-lactamase from Bacillus cereus, strain 569/H/9, has been purified to apparent homogeneity. Nonionic detergent (0.5% Triton X-100) is required to keep the enzyme (traditionally called gamma-penicillinase and now called beta-lactamase III) in solution. Antibodies to beta-lactamase III have been prepared, and the membrane-bound enzyme is immunochemically distinct from the extracellular enzymes. beta-Lactamase III has a molecular weight of 31 500, in contrast to the extracellular enzymes beta-lactamase I and beta-lactamase II which have molecular weights of 30 000 and 22 000, respectively. The isoelectric point of beta-lactamase III is pH 6.8, whereas beta-lactamase I and beta-lactamase II have isoelectric points about 8.6 and 8.3. The amino acid composition of beta-lactamase III differs from those of beta-lactamase I and beta-lactamase II; however, the difference index between the compositions of beta-lactamase I and beta-lactamase III (52%) suggests relatedness. beta-Lactamase III is inactivated by 6 beta-bromopenicillanic acid and by the sulfone of 6 alpha-chloropenicillanic acid, and cephalosporins are poorer substrates than penicillins. beta-Lactamase III may be a membrane-bound class A beta-lactamase.
D000596:Amino Acids / Q000032:analysis; D001409:Bacillus cereus / Q000201:enzymology*; D002462:Cell Membrane / Q000201:enzymology; D002510:Cephalosporinase / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D005779:Immunodiffusion; D007700:Kinetics; D008970:Molecular Weight; D010405:Penicillinase / Q000378:metabolism*; D013379:Substrate Specificity
D000596:Amino Acids; D002510:Cephalosporinase; D010405:Penicillinase