Mechanistic model for the firefly luciferin regeneration in biomimetic conditions: a model for the in vivo process?

Abstract

The emission of light by fireflies involves the enzymatic oxidation of firefly luciferin and ends up in the formation of 2-cyano-6-hydroxybenzothiazole, and this is recycled back to luciferin by condensation with cysteine. In this work, we suggest a mechanism for this transformation that operates under mild conditions that are similar to in vivo environments (i.e. biomimetic); the rate-determining step consists of an intermolecular nucleophilic attack from the cysteine thiolate on the nitrile, catalysed by a specific base, followed by a complex sequence of intramolecular reactions which are highly dependent on the medium pH.