Open AccessOHIO‐1 β‐lactamase mutants: Asp179Gly mutation confers resistance to ceftazidime
Author(s) -
Bonomo Robert A,
Rudin Susan D,
Shlaes David M
Publication year - 1997
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1997.tb10439.x
Subject(s) - ceftazidime , mutant , microbiology and biotechnology , mutation , chemistry , biology , genetics , bacteria , gene , pseudomonas aeruginosa
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 ( K m ≥500 μM), the K m of the Asp179Gly mutant β‐lactamase was measured to be 7 μM and the V max was 0.13 μM/min. The minimum inhibitory concentrations, K m , and V max 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.