Abstract
AbstractA plethora of dimeric natural products exist with diverse chemical structures and biological activities. A major strategy for dimerization is aryl coupling catalyzed by cytochrome P450 or laccase. Actinorhodin (ACT) from Streptomyces coelicolor A3(2) has a dimeric pyranonaphthoquinone structure connected by a C−C bond. In this study, we identified an NmrA‐family dimerizing enzyme, ActVA‐ORF4, and a cofactor‐independent oxidase, ActVA‐ORF3, both involved in the last step of ACT biosynthesis. ActVA‐ORF4 is a unique NAD(P)H‐dependent enzyme that catalyzes the intermolecular C−C bond formation using 8‐hydroxydihydrokalafungin (DHK‐OH) as the sole substrate. On the other hand, ActVA‐ORF3 was found to be a quinone‐forming enzyme that produces the coupling substrate, DHK‐OH and the final product, ACT. Consequently, the functional assignment of all essential enzymes in the biosynthesis of ACT, one of the best‐known model natural products, has been completed.
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