ISSN:
1574-6968
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
The Asp179Gly mutant of the OHIO-1 β-lactamase, an SHV enzyme, was constructed to investigate the effect of disruption of the omega loop on β-lactamase activity in this class A enzyme. In Escherichia coli DH5α the strain possessing the Asp179Gly mutation of the OHIO-1 β-lactamase demonstrated increased susceptibility to all β-lactams except ceftazidime and ceftriaxone. The minimum inhibitory concentrations for ceftazidime and ceftriaxone increased from 0.25 and 0.015 μg/ml to 4.0 and.25 μg/ml respectively. For ceftazidime, a substrate not hydrolyzed by the wild-type enzyme (Km≥500 μM), the Km of the Asp179Gly mutant β-lactamase was measured to be 7 μM and the Vmax was 0.13 μM/min. The minimum inhibitory concentrations, Km, and Vmax for all other β-lactams decreased. Our analysis of this OHIO-1 β-lactamase mutant suggests that disruption of the salt bridge in the omega loop by substitution of a glycine at position 179 markedly decreases the catalytic efficiency of the enzyme.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1574-6968.1997.tb10439.x
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