Upon binding the substrate, the enzyme catalyzes an oxygenation, producing a very short-lived hydroperoxide that cyclizes into a dioxetanone structure, which collapses, releasing a CO(2) molecule. The spontaneous breakdown of the dioxetanone releases the energy (about 50 kcal/mole) that is necessary to generate the excited state of the coelenteramide product, which is the singlet form of the monoanion. In vivo the product undergoes the process of nonradiative energy transfer to an accessory protein, a green fluorescent protein (GFP), which results in green bioluminescence. In vitro, in the absence of GFP, the product emits blue light. coelenterazine h + O2 = CO2 + excited coelenteramide h monoanion + H(+) + hnu Optimum pH is 7.4. Optimum temperature is 32 degrees Celsius. Monomer. This luciferase produces light with a wavelength of 480 nm. In presence of a green fluorescence protein (GFP) it produces a green fluorescence at 509 nm.