Discovery of a Two-Component Monooxygenase SnoaW/SnoaL2 Involved in Nogalamycin Biosynthesis

SummaryNogalamycin is an anthracycline polyketide antibiotic that contains two deoxysugars, at positions C-1 and C-7. Previous biosynthetic studies conducted in vivo affiliated snoaL2 with an unusual C-1 hydroxylation reaction, but in 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′,4′-demethoxy-nogalose-nogalamycinone. The C-1 hydroxylation activity was successfully reconstructed in vitro in the presence of the two enzymes, NAD(P)H and the substrates. Based on relative reaction efficiencies, 3′,4′-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.

Graphical AbstractFigure optionsDownload full-size imageDownload high-quality image (275 K)Download as PowerPoint slideHighlights► Previously a cofactor-independent C-1 hydroxylase SnoaL2 has been identified in vivo ► Here, we show that SnoaL2 requires an atypical SDR SnoaW for activity ► The catalytic concept of the reaction is inspired by flavin chemistry ► A two-component monooxygenase involved in nogalamycin biosynthesis is presented