-!- This enzyme has been studied from the soft coral Renilla reniformis. -!- Before the reaction occurs the substrate is sequestered by a coelenterazine-binding protein. -!- Elevation in the concentration of calcium ions releases the substrate, which then interacts with the luciferase. -!- 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.