Light regulation of flavin reduction by NAD(P)H: Activation of 2-haloacrylate hydratase

We report a novel light-dependent activation mechanism for 2-haloacrylate hydratase (2HAH), a flavin-dependent dehalogenase. Initial assays revealed inconsistent enzyme activity, stabilized only after chemical reduction or exposure to bright light. Spectroscopic analysis showed that light accelerates flavin reduction by NAD(P)H, completing in 30 s under bright light versus slow reduction in the dark. Blue light specifically triggered full activation, while red light had no effect. Sequence and structural analyses indicate that 2HAH does not share homology with known light-sensitive flavoproteins, suggesting an uncharacterized regulatory mechanism. These findings advance our understanding of flavin enzyme regulation and introduce light as a potential tool for modulating 2HAH activity.