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Citrobacter diversus ULA-27 beta-lactamases. Improved purification and general properties.
G Amicosante1, A Oratore, N Franceschini
1Università degli Studi dell'Aquila, Dipartimento di Scienze e Tecnologie Biomediche e di Biometria, Italy.
The Biochemical Journal
|September 15, 1988
Summary
Two beta-lactamase enzymes were purified from Citrobacter diversus ULA-27. These enzymes show broad-spectrum activity, effectively hydrolyzing cephalosporins but not azthreonam.
Area of Science:
- Microbiology
- Enzymology
- Biochemistry
Background:
- Beta-lactamases are enzymes that confer bacterial resistance to beta-lactam antibiotics.
- Citrobacter diversus is an opportunistic pathogen, and understanding its resistance mechanisms is crucial.
Purpose of the Study:
- To purify and characterize beta-lactamase enzymes encoded by the chromosome of Citrobacter diversus ULA-27.
- To determine the substrate specificity and kinetic properties of these enzymes.
Main Methods:
- Purification of beta-lactamases using biochemical techniques.
- Isoelectric focusing to determine isoelectric points.
- Enzyme kinetics assays to measure hydrolysis rates for various beta-lactam substrates.
Main Results:
- Two distinct beta-lactamases were isolated with isoelectric points of 6.8 and 6.2.
- Both enzymes displayed Mr values of approximately 29,000.
- The enzymes exhibited broad substrate specificity, efficiently hydrolyzing certain cephalosporins.
- Hydrolysis rates for cloxacillin, methicillin, and imipenem were very low.
- No detectable hydrolysis of azthreonam was observed.
Conclusions:
- Citrobacter diversus ULA-27 possesses at least two chromosomally encoded beta-lactamases with distinct properties.
- These enzymes contribute to the bacterium's resistance profile, particularly against certain cephalosporins.
- The limited activity against specific antibiotics like azthreonam suggests potential for therapeutic strategies targeting these enzymes.