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Induction of beta-lactamase in Proteus vulgaris
Abstract:
Various beta-lactam antibiotics, including monocyclic beta-lactams, induced the beta-lactamase of Proteus vulgaris; when clinical isolates were induced by benzylpenicillin, each strain produced a single beta-lactamase but the activity per milligram dry weight differed from strain to strain. The beta-lactamases of the P. vulgaris strains were heterogeneous with respect to their isoelectric points, but had almost the same specific activities, substrate specificities and Michaelis constants. The kinetics of beta-lactamase formation were investigated in three strains, each with a different beta-lactamase activity. Differential rates of enzyme synthesis and peak activity depended on the concentration of inducer. The plots of the reciprocals of the differential rates versus the reciprocals of the inducer concentrations were linear, and the maximum rate of enzyme synthesis and the concentration of the inducer giving half-maximum induction were determined from this double reciprocal plot. The maximum rates of enzyme synthesis were different in the three strains. The kinetic analysis of beta-lactamase formation revealed that the beta-lactamase activities in a single bacterial species were determined by differences in the rate of enzyme synthesis and not by differences in the properties of the enzyme.
Insights
Beta-lactam antibiotics induce beta-lactamase in Proteus vulgaris. Enzyme activity differences between strains are due to varying synthesis rates, not enzyme properties, impacting antibiotic resistance.
Area of Science:
- Microbiology
- Enzymology
- Biochemistry
Background:
- Beta-lactam antibiotics are crucial therapeutics.
- Beta-lactamase enzymes confer bacterial resistance.
- Proteus vulgaris is a relevant model organism.
Purpose of the Study:
- Investigate beta-lactamase induction in Proteus vulgaris.
- Characterize beta-lactamase properties and kinetics.
- Determine factors influencing enzyme activity variations.
Main Methods:
- Induction of beta-lactamase using various beta-lactam antibiotics.
- Characterization of enzyme properties (isoelectric points, specific activity, substrate specificity, Michaelis constants).
- Kinetic analysis of enzyme formation using double reciprocal plots.
Main Results:
- Proteus vulgaris strains produced a single beta-lactamase when induced by benzylpenicillin.
- Beta-lactamases were heterogeneous in isoelectric points but similar in specific activity, substrate specificity, and Michaelis constants.
- Enzyme synthesis rates varied significantly between strains, affecting overall beta-lactamase activity.
Conclusions:
- Beta-lactamase activity in Proteus vulgaris is primarily determined by the rate of enzyme synthesis.
- Differences in enzyme properties do not account for activity variations between strains.
- Understanding these kinetics is vital for antibiotic resistance research.