Monovalent ion-dependent bioluminescence photoprotein. Displays an emission peak at 470 nm (blue light). Trace amounts of monovalent ion trigger the intramolecular oxidation of the chromophore, didehydrocoelenterazine, with the emission of light. Photogenic gland (at protein level). On the 2D-gel the determined MW of this protein is: 60 kDa. Belongs to the carbon-nitrogen hydrolase superfamily. BTD/VNN family.