bekanamycin and isepamicin

Directed evolution by random PCR mutagenesis of the gene for the aminoglycoside 2''-IIa phosphotransferase generated R92H/D268N and N196D/D268N mutant enzymes, resulting in elevated levels of resistance to amikacin and isepamicin but not to other aminoglycoside antibiotics. Increases in the activities of the mutant phosphotransferases for isepamicin are the result of decreases in K(m) values, while improved catalytic efficiency for amikacin is the result of both a decrease in K(m) values and an increase in turnover of the antibiotic. Enzymes with R92H, D268N, and D268N single amino acid substitutions did not result in elevated MICs for aminoglycosides.

Topics: Aged; Amikacin; Amino Acid Substitution; Anti-Bacterial Agents; Bacterial Proteins; Base Sequence; Directed Molecular Evolution; DNA Primers; DNA, Bacterial; Drug Resistance, Bacterial; Escherichia coli; Gentamicins; Humans; Kinetics; Models, Molecular; Molecular Sequence Data; Mutagenesis; Mutation; Phosphotransferases (Alcohol Group Acceptor); Protein Structure, Tertiary; Recombinant Proteins; Sequence Homology, Amino Acid