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

: Siitonen V, Blauenburg B, Kallio P, Mantsala P, Metsa-Ketela M

Publisher: CELL PRESS

: 2012

: Chemistry and Biology

: CHEMISTRY & BIOLOGY

: CHEM BIOL

: 5

: 19

: 5

: 638

: 646

: 9

: 1074-5521

DOI: https://doi.org/10.1016/j.chembiol.2012.04.009

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.