The same aminoglycoside 2"-adenylyltransferase was isolated from four 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 second 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 Cla. The pH optimum was 7.8 to 8.0 for every substrate, and the molecular weight of the enzyme molecule was estimated at approximately 29,000. Genetic experiments clearly established that both enzymes were expressed by a conjugative plasmid.
Thirteen Gurvularia and related species were examined and the following metabolites obtained: brefeldin A, curvularin, curvulin, curvulinic acid derivatives, D-mannitol, 1,4,5,8-tetrahydroxy-2,6-dimethylanthraquinone, saturated and unsaturated fatty acids, and fatty acid esters.
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