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beta-Lactam synthetase: a new biosynthetic enzyme
B O Bachmann1, R Li, C A Townsend
1Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA.
Summary
Bacterial resistance to antibiotics like penicillin is a major concern. Researchers discovered a new enzyme, beta-lactam synthetase, crucial for clavulanic acid biosynthesis, offering insights into antibiotic development.
Area of Science:
- Microbiology
- Biochemistry
- Enzymology
Background:
- Bacterial resistance to beta-lactam antibiotics is primarily due to beta-lactamases.
- Clavulanic acid effectively inhibits beta-lactamases, combating resistant infections.
- Biosynthesis pathways for clavulanic acid and penicillin differ significantly.
Purpose of the Study:
- To elucidate the mechanism of beta-lactam ring formation in clavulanic acid biosynthesis.
- To identify and characterize the enzyme responsible for this critical step.
- To investigate the potential broader implications of this pathway in nature.
Main Methods:
- Gene knockout (insertional inactivation) in Streptomyces clavuligerus.
- Chemical complementation of a blocked mutant.
- Enzyme overexpression and in vitro activity assays.
- Amino acid sequence comparisons.
Main Results:
- A novel ATP/Mg2+-dependent enzyme, beta-lactam synthetase (beta-LS), was identified.
- Inactivation of the beta-LS gene abolished clavulanic acid production and accumulated N2-(carboxyethyl)-L-arginine (CEA).
- The beta-LS enzyme catalyzes the conversion of CEA to deoxyguanidinoproclavaminic acid (DGPC) using ATP/Mg2+.
Conclusions:
- Beta-lactam synthetase is essential for clavulanic acid biosynthesis.
- The mechanism of beta-lactam formation by beta-LS is distinct from penicillin biosynthesis.
- This novel beta-lactam formation pathway may be widespread and related to asparagine synthesis.