1. An enzyme that aids the oxidation of luciferin in the cells of organisms that emit light.
2. An enzyme which is present in fireflies.
3. A group of enzymes that produce bioluminescence by oxidizing luciferin.
4. An enzyme that catalyzes, in the presence of adenosine triphosphate, the transfer of an electron from luciferin to oxygen, with the emission of light.

The reaction is the basis of the bioluminescence which occurs in fireflies, glow worms, certain bacteria, and some fungi.