Pink-colored Cypridina luciferase from Cypridina (Vargula) hilgendorfii: Oxygen-triggered luminescence reaction following NAD(P)H-FMN flavin reductase reaction.

Abstract

The pink-colored Cypridina luciferase (CypLase∗) from Cypridina (Vargula) hilgendorfii contains an unknown chromophore (CypL∗), derived from Cypridina luciferin (CypL). When CypLase∗ was treated with NAD(P)H-FMN flavin reductase (FRase) and NADH, the luminescence intensity in the reaction mixture increased significantly after gentle tapping. This observation suggests that CypL∗ in CypLase is enzymatically converted to CypL by the reduced flavin (FMNH₂) through the FRase reaction, and the resulting complex of CypL and CypLase reacts with O₂ to emit light. Therefore, CypL∗ might be a dehydrogenated form of CypL and might serve as another storage form in Cypridina specimens.