The Chemistry of Bioluminescence: An Analysis of Chemical Functionalities

Firefly luciferase is one of the most studied bioluminescent systems, both theoretically and experimentally. Herein we review the current understanding of the bioluminescent process from a chemical functionality perspective based on those investigations. Three key components are emphasized: the chemiluminophore, the electron-donating fragment, and how these are affected by the substrateenzyme interaction. The understanding is based on details of how the peroxide ?O?O? bond supports the production of electronically excited products and how the charge-transfer (CT) mechanism, with the aid of an electron-donating group, lowers the activation barrier to support a reaction occurs in living organisms. For the substrateenzyme complex it is demonstrated that the enzyme can affect the hydrogen-bonding around the CT-controlling group, resulting in a mechanism for color modulation. Finally, we analyse other luciferinluciferase systems and compare them to the key chemical functionalities of the fragments of the luciferinluciferase complex with respect to similarities and differences.