New plasmid-mediated aminoglycoside adenylyltransferase of broad substrate range that adenylylates amikacin

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Abstract
He same aminoglycoside 2"-adenylyltransferase was isolated from 4 gram-negative species which were among a random group of gentamicin-resistant isolates from the same hospital. The enzyme was partially purified from a crude extract which also contained a 2nd modifying enzyme identified as APH(3'')-I. The substrate range of the new aminoglycoside 2"-adenylyltransferase included the newer aminoglycosides sisomicin and amikacin, but showed much-reduced activity against gentamicins C2 and C1a. The pH optimum was 7.8-8.0 for every substrate, and the MW of the enzyme molecule was estimated at .apprx. 29,000. Genetic experiments clearly established that both enzymes were expressed by a conjugative plasmid.