What is Luciferase?
Luciferase is a class of oxidative enzymes applied in bioluminescence assays. The most commonly used one is the firefly luciferase from the firefly Photinus pyralis. Therefore the laboratory reagent "Firefly luciferase" refers to P. pyralis luciferase.
Moreover, many other organisms produce light using different luciferases via a variety of light-emitting reactions.
How does Luciferase work?
Firefly luciferase catalyzes a two-steps chemical reaction:
luciferin + ATP → luciferyl adenylate + PP
luciferyl adenylate + O2 → oxyluciferin + AMP + light
electronically excited state oxyluciferin is formed in this reaction with light being emitted. A photon of light is released as oxyluciferin returns to the ground state in the reaction.
Bacterial luciferase catalyzes an oxidative reaction as well:
FMNH2 + O2 + RCHO → FMN + RCOOH + H2O + light
In the reaction, a reduced flavin mononucleotide participates in oxidization of a long-chain aliphatic aldehyde and an aliphatic carboxylic acid. An excited hydroxyflavin intermediate is formed in the reaction, and it's then dehydrated to FMN to emit blue-green light
Firefly luciferase generates light from luciferin in a multistep process. First, D-luciferin is adenylated by MgATP to form luciferyl adenylate and pyrophosphate. After activation by ATP, luciferyl adenylate is oxidized by molecular oxygen to form a dioxetanone ring. A decarboxylation reaction forms an excited state of oxyluciferin, which tautomerizes between the keto-enol form. The reaction finally emits light as oxyluciferin returns to the ground state.