Oxidoreductases;
Acting on single donors with incorporation of molecular oxygen (oxygenases);
With incorporation of one atom of oxygen (internal monooxygenases or internal mixed-function oxidases)
excited state blue fluorescent protein;
CO2 [CPD:C00011];
apoaequorin containing coelenterazine;
aequorin;
[aequorin] 1,2-dioxetan-3-one
Comment
Ca2+-regulated photoproteins are found in a variety of bioluminescent marine organisms, mostly coelenterates, and are responsible for their light emission. The best studied enzyme is from the jellyfish Aequorea victoria. The enzyme tightly binds the imidazolopyrazinone derivative coelenterazine, which is then peroxidized by oxygen. The hydroperoxide is stably bound until three Ca2+ ions bind to the protein, inducing a structural change that results in the formation of a 1,2-dioxetan-3-one ring, followed by decarboxylation and generation of a protein-bound coelenteramide in an excited state. The calcium-bound protein-product complex is known as a blue fluorescent protein. In vivo the energy is transferred to a green fluorescent protein (GFP) by Forster resonance energy transfer. In vitro, in the absence of GFP, coelenteramide emits a photon of blue light while returning to its ground state.
