Chemistry & Biology 2012-05-25

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

Vilja Siitonen, Bastian Blauenburg, Pauli Kallio, Pekka Mäntsälä, Mikko Metsä-Ketelä, Vilja Siitonen, Bastian Blauenburg, Pauli Kallio, Pekka Mäntsälä, Mikko Metsä-Ketelä

Index: Chem. Biol. 19(5) , 638-46, (2012)

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Abstract

Nogalamycin 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.