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Peptidase activity of beta-lactamases
1Centre d'Ingénierie des Protéines and Laboratoire d'Enzymologie, Université de Liège, Institut de Chimie B6, Sart Tilman, B-4000 Liège, Belgium.
The Biochemical Journal
|July 7, 1999
Summary
Beta-lactamases, enzymes typically breaking down antibiotics, can also hydrolyze specific peptides. This unexpected peptidase activity, though low, reveals shared catalytic mechanisms with dd-peptidases.
Area of Science:
- Biochemistry
- Enzymology
- Microbiology
Background:
- Beta-lactamases are primarily known for hydrolyzing beta-lactam antibiotics.
- Their potential peptidase activity has been largely overlooked.
- Understanding enzyme promiscuity is crucial for drug discovery and resistance mechanisms.
Purpose of the Study:
- To investigate the peptidase activity of various beta-lactamase classes.
- To compare the substrate specificity of beta-lactamases with known dd-peptidases.
- To explore the structural and stereoelectronic basis for observed activities.
Main Methods:
- Enzymatic assays using N-acylated dipeptides and tripeptides.
- Kinetic analysis (kcat/Km) to quantify hydrolysis rates.
- Comparative analysis with established dd-peptidases.
Main Results:
- Representatives from all beta-lactamase classes exhibited low but significant N-acylated dipeptide hydrolysis.
- Class C beta-lactamase from Enterobacter cloacae P99 showed the highest 'peptidase' activity.
- Beta-lactamases preferred phenylacetyl- and benzoyl-d-Ala-d-Ala over preferred dd-peptidase substrates.
Conclusions:
- Beta-lactamases possess latent peptidase activity, challenging the traditional view.
- Geometric and stereoelectronic factors likely explain the substrate preferences and limitations in both enzyme types.
- This promiscuity offers insights into enzyme evolution and potential new therapeutic targets.