Source of oxygen in the CO 2 produced in the bioluminescent oxidation of firefly luciferin

Abstract

Incorporation of 18O into the CO2 produced in the bioluminescent oxidation of firefly luciferin was studied. In H216O medium with 18O2, the product CO2 contained up to 75% C16O18O, showing that one O of the product CO2 arose from the O2 that oxidized luciferin. This result is consistent with a dioxetane mechanism. Analysis of mass spectral data of the CO2 obtained in high-enrichment H218O medium with 16O2 gas indicated the presence of .apprx. 20% contaminating CO2, which contributed .apprx. 70% of the total incorporated 18O. The values of incorporated 18O in H218O medium with 16O2 gas had no significance in this context. Data obtained with luciferases of the American firefly Photinus and Japanese firefly Luciola were similar.