Photoprotein

Photoproteins refer to bioluminescent proteins from luminous organisms. These proteins do not exhibit a luciferin-luciferase reaction, that is, a normal enzyme-substrate reaction. Instead, these proteins display luminescence proportional to the amount of the protein. Such proteins are stable as a luciferin-photoprotein complex, often until the addition of another required factor, such as Ca⁺⁺ for the photoprotein aequorin.

The term was first used to describe the unusual chemistry of the chaetopteris luminescent system.