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Flavoenzyme CrmK-mediated substrate recycling in caerulomycin biosynthesis

2016; Royal Society of Chemistry; Volume: 7; Issue: 8 Linguagem: Inglês

10.1039/c6sc00771f

2041-6539

Yiguang Zhu, Marie-Ève Picard, Qingbo Zhang, Julie Barma, Xavier Murphy Després, Xiangui Mei, Liping Zhang, Jean‐Baptiste Duvignaud, Manon Couture, Weiming Zhu, Rong Shi, Changsheng Zhang,

Pharmacogenetics and Drug Metabolism

Substrate salvage or recycling is common and important for primary metabolism in cells but is rare in secondary metabolism. Herein we report flavoenzyme CrmK-mediated shunt product recycling in the biosynthesis of caerulomycin A (CRM A 1), a 2,2'-bipyridine-containing natural product that is under development as a potent novel immunosuppressive agent. We demonstrated that the alcohol oxidase CrmK, belonging to the family of bicovalent FAD-binding flavoproteins, catalyzed the conversion of an alcohol into a carboxylate via an aldehyde. The CrmK-mediated reactions were not en route to 1 biosynthesis but played an unexpectedly important role by recycling shunt products back to the main pathway of 1. Crystal structures and site-directed mutagenesis studies uncovered key residues for FAD-binding, substrate binding and catalytic activities, enabling the proposal for the CrmK catalytic mechanism. This study provides the first biochemical and structural evidence for flavoenzyme-mediated substrate recycling in secondary metabolism.