摘要
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Summary
Nogalamycin is an anthracycline polyketide antibiotic that contains two deoxysugars, at positions C-1 and C-7. Previous biosynthetic studies conducted in聽vivo affiliated snoaL2 with an unusual C-1 hydroxylation reaction, but in聽vitro activity was not established. Here, we demonstrate that inactivation of either snoaL2 or snoaW resulted in accumulation of two nonhydroxylated metabolites, nogalamycinone and a novel anthracycline 3鈥?4鈥?demethoxy-nogalose-nogalamycinone. The C-1 hydroxylation activity was successfully reconstructed in聽vitro in the presence of the two enzymes, NAD(P)H and the substrates. Based on relative reaction efficiencies, 3鈥?4鈥?demethoxy-nogalose-nogalamycinone was identified as the likely natural substrate. A biosynthetic model was established where the atypical short-chain alcohol dehydrogenase SnoaW reduces the anthraquinone to a dihydroquinone using NADPH, which enables activation of oxygen and formation of a hydroperoxy intermediate. Finally, protonation of the intermediate by SnoaL2 yields the 1-hydroxylated product.
