Evidence for multiple forms of type I chromosomal β-lactamase in Pseudomonas aeruginosa

M. L. Gates, C. C. Sanders, R. V. Goering, W. E. Sanders

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The multiple stages of derepression of the type I chromosomal beta-lactamase in Pseudomonas aeruginosa were examined. Mutants partially and fully derepressed for beta-lactamase were selected from a wild-type clinical isolate. An analysis of the beta-lactamase produced by these mutants and the induced wild type revealed significant differences in the products of derepression at each stage. Beta-lactamase produced by the fully derepressed mutant showed a lower affinity (K(m), 0.113 mM) for cephalothin than that produced by the partially derepressed mutant (K(m), 0.049 mM). However, due to a very large V(max), the former possessed a much greater hydrolytic efficiency. Differences in substrate profile were also noted. Only beta-lactamase from the fully derepressed mutant hydrolyzed cefamandole, cefoperazone, and cefonicid. The partially derepressed mutant possessed a single beta-lactamase band with a pI of 8.4. The fully derepressed mutant possessed this band and an additional major band with a pI of 7.5. Induction of the wild type with cefoxitin produced both bands. The changes in physiologic parameters of the enzymes produced in the different stages of derepression suggest a complex system for beta-lactamase expression in P. aeruginosa. This may involve at least two distinct structural regions, each of which is under control of the same repressor.

Original languageEnglish (US)
Pages (from-to)453-457
Number of pages5
JournalAntimicrobial agents and chemotherapy
Issue number3
StatePublished - 1986

All Science Journal Classification (ASJC) codes

  • Pharmacology
  • Pharmacology (medical)
  • Infectious Diseases


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