Proposed mechanism for the bacterial bioluminescence reaction involving a dioxirane intermediate.

We propose here a verifiable mechanism for the bacterial bioluminescence reaction involving a dioxirane intermediate. Participation of the dioxirane predicts either formation of an excited carbonyl, rather than the flavin, as the primary excited state in the reaction, or, through a CIEEL mechanism, the C4a hydroxyflavin or the chromophore of a secondary emitter protein could become excited. We propose energy transfer from the primary excited state to the C4a hydroxyflavin in the absence of the lumazine protein or the yellow fluorescence protein, while in the presence of either of the secondary emitter proteins, excitation energy would be transferred to the second protein-bound chromophore. The mechanism is similar to other currently discussed mechanisms, except in the final steps leading to the primary excited state. The mechanism is consistent with the known details of the reactions of dioxiranes and of flavins and with recent studies of the secondary emitter proteins and bacterial luciferases.