A QM/MM Study on the Initiation Reaction of Firefly Bioluminescence-Enzymatic Oxidation of Luciferin

Among all bioluminescent organisms, the firefly is the most famous, with a high luminescent efficiency of 41%, which is widely used in the fields of biotechnology, biomedicine and so on. The entire bioluminescence (BL) process involves a series of complicated in-vivo chemical reactions. The BL is initiated by the enzymatic oxidation of luciferin (LH2). However, the mechanism of the efficient spin-forbidden oxygenation is far from being totally understood. Via MD simulation and QM/MM calculations, this article describes the complete process of oxygenation in real protein. The oxygenation of luciferin is initiated by a single electron transfer from the trivalent anionic LH2 (L3-) to O-2 to form (1)[L center dot 2- horizontal ellipsis O-2(center dot-)]; the entire reaction is carried out along the ground-state potential energy surface to produce the dioxetanone (FDO-) via three transition states and two intermediates. The low energy barriers of the oxygenation reaction and biradical annihilation involved in the reaction explain this spin-forbidden reaction with high efficiency. This study is helpful for understanding the BL initiation of fireflies and the other oxygen-dependent bioluminescent organisms.

Automated summary

Among bioluminescent organisms, fireflies are the most famous for their high luminescent efficiency. Through molecular dynamics simulation and calculations, the efficient oxygenation mechanism of luciferin in fireflies has been studied, shedding light on the high efficiency of their bioluminescence initiation.