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ENZYME

ENZYME entry: EC 1.13.12.24

PURL: https://purl.expasy.org/enzyme/EC/1.13.12.24
Accepted Name
calcium-regulated photoprotein
Alternative Name(s)
aequorin
berovin
Ca(2+)-regulated photoprotein
calcium-activated photoprotein
clytin
halistaurin
mitrocomin
mnemiopsin
obelin
vialidin
Reaction catalysed
apo-[aequorin] + coelenterazine + 3 Ca(2+) + O2 = excited state-[aequorin] + CO2
Comment(s)
  • Ca(2+)-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 Ca(2+) 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 Foerster resonance energy transfer.
  • In vitro, in the absence of GFP, coelenteramide emits a photon of blue light while returning to its ground state.
Cross-references
BRENDA1.13.12.24
EC2PDB1.13.12.24
ExplorEnz1.13.12.24
KEGG Ligand Database for Enzyme Nomenclature1.13.12.24
IUBMB Enzyme Nomenclature1.13.12.24
MEDLINEFind literature relating to 1.13.12.24
MetaCyc1.13.12.24
Rhea expert-curated reactions1.13.12.24

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