Open AccessOHIO‐1 β‐lactamase resistant to mechanism‐based inactivators
Author(s) -
Bonomo Robert A,
CurrieMcCumber C,
Shlaes David M
Publication year - 1992
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.1574-6968.1992.tb05237.x
Subject(s) - mechanism (biology) , chemistry , computational biology , microbiology and biotechnology , combinatorial chemistry , biology , philosophy , epistemology
Abstract Spontaneous mutants of OHIO‐1 β‐lactamase, an SHV‐1 family enzyme, resistant to inactivation by clavulanic acid, sulbactam and tazobactam, have been isolated. The resistant mutant (M4) was inhibited by 100 μg/ml ampicillin plus 32 μg/ml clavulanic acid compared to ≤2 μg/ml clavulanic acid required for the parent strain. The pI of the mutant beta‐lactamase was 7.0, identical to the parent enzyme. Kinetic parameters showed that the M4 enzyme had an increased V max /K m ratio for all beta‐lactam substrates compared to the parent enzyme. The apparent K i for clavulanic acid, sulbactam and tazobactam was 15.1, 182 and 18 μM, respectively, up to 70‐fold higher than the parent enzyme. Partial nucleotide sequencing revealed that the mutant enzyme had a predicted methionine 69 → isoleucine 69 substitution accounting for the observed changes in substrate specificity.