Structure-Sequence Guided Discovery of Highly Efficient Curcumin Reductase Enables Biocatalytic Reductive Editing of Curcuminoids

Tetrahydrocurcumin, a major hydrogenated curcumin derivative with improved stability and bioavailability, represents a promising ingredient for functional foods and nutraceuticals. Curcumin reductases (CurAs) catalyze the eco-friendly enzymatic conversion of curcumin to tetrahydrocurcumin, yet few CurA homologues have been identified. Here, using two characterized CurAs as seed sequences, we developed a data-driven screening pipeline integrating sequence clustering and structure-based evaluation. Functional characterization of 15 prioritized candidates identified RmCurA from Rhodomicrobium as the top-performing enzyme. It rapidly and fully converts curcumin to tetrahydrocurcumin within 8 min at nanomolar enzyme loading and favors natural demethylated curcuminoids over heavily methylated analogs. Molecular dynamics simulations revealed that RmCurA forms an obligate homodimer with rigid, stable architecture, and its dual energy minima indicative of interconvertible functional conformations supporting high catalytic activity. This work establishes an efficient biocatalytic route toward tetrahydrocurcumin and provides a general framework to discover high-performance enzymes for natural product modification.