Novel Mechanism of Bioluminescence: Oxidative Decarboxylation of a Moiety Adjacent to the Light Emitter of Fridericia Luciferin

Abstract

An ovel luciferin from ab ioluminescent Siberian earthworm Fridericia heliota was recently described. In this study,the Fridericia oxyluciferin was isolated and its structure elucidated. The results provideinsight into anovel bioluminescence mechanism in nature.O xidative decarboxylation of al ysine fragment of the luciferin supplies energy for light generation, while af luorescent CompX moiety remains intact and serves as the light emitter.Bioluminescence (BL)-the production of "cold light" by al iving organism-is generally mediated by the oxidation of asmall organic molecule called luciferin by molecular oxygen in ar eaction catalyzed by as pecific luciferase enzyme.[1] We recently reported the structure of an ovel luciferin from the Siberian bioluminescent earthworm Fridericia heliota.[2] We found this luciferin to be ak ey component of an ovel ATPdependent bioluminescent system, along with as pecific luciferase,A TP,M g 2 + ions,a nd molecular oxygen [3] The Fridericia luciferin turned out to be an unusual peptide formed from oxalic acid, l-lysine,m odified tyrosine (CompX [4] ), and g-aminobutyric acid residues.Herein, we report the structural elucidation of the Fridericia luciferin oxidation product, i.e., the oxyluciferin. Ther esults provide as tructural basis for understanding the novel light generation mechanism underlying the bioluminescence of Fridericia heliota.Oxyluciferin was prepared by mixing 0.18 mg of synthetic Fridericia luciferin [2] with excess ATPa nd crude Fridericia luciferase obtained through partial purification of protein extract from 40 go ft he worm biomass [5] (Scheme 1, see the Supporting Information for details). Ther eaction mixture produced constant eye-visible luminescence and the reaction course was monitored by HPLC analysis of aliquots (Figure 1), which showed formation of am ajor product of luciferin oxidation with ar etention time of 18.2 min. After 25 h, approximately 62 %o ft he luciferin was consumed. At this point, the reaction was stopped by adding formic acid and the mixture was subjected to solid-phase extraction with subsequent HPLC to give 0.8 optical density units of oxyluciferin (absorption at 310 nm).

Progress in the Study of Bioluminescent Earthworms

“…The role of the luciferin adenylate as an intermediate in Fridericia bioluminescence was confirmed by a chemiluminescent study of a model luciferin‐ tert ‐butyl ester at the lysine carboxy group . The observed chemiluminescence of a model compound under the action of bases suggested that the formation of ester at the lysine carboxyl group facilitates the deprotonation of lysine α ‐H and further oxidation to form peroxide intermediate.…”

“…Based on the structure of Fridericia oxyluciferin, obtained by enzymatic oxidation, a new light‐generation mechanism, greatly resembling that of the fireflies, was proposed (Scheme ) . Presumably, in the first step, Fridericia luciferase catalyzes the reaction between luciferin and ATP, leading to the formation of luciferin–adenylate conjugate at the lysine carboxyl group.…”

Chemiluminescence and Bioluminescence as an Excitation Source in the Photodynamic Therapy of Cancer: A Critical Review

“…Several BL and CL systems have been intensively studied, which has allowed the development of several new techniques. These rely on various intrinsic and advantageous characteristics: specificity, sensitivity, speed of reaction, high quantum yields and possibility for color modulation.…”

“…BL can be considered as as ub-type of chemiluminescence (CL), which consists of the chemical productionofl ight as ar esult of chemical reactions. [14,15] Several BL and CL systemsh ave been intensively studied, [14][15][16][17][18][19][20][21][22][23][24][25] which has allowed the development of several new techniques. These rely on variousi ntrinsic and advantageous characteristics:s pecificity,s ensitivity,s peed of reaction, high quantum yields and possibilityf or color modulation.…”

Luciferin-luciferase system of marine polychaete Chaetopterus variopedatus

“…Ионы двухвалентных металлов в различных биолюминесцентных системах обычно служат кофакторами люцифераз и не расходуются в реакциях светоизлучения. В качестве примеров можно привести Mg 2+ в люциферин-люциферазной системе энхитреиды Fridericia heliota [8] или Ca 2+ в различных фотопротеиновых системах [1]. В отличие от этого Fe 2+ в реакции биолюминесценции C. variopedatus необратимо превращается в Fe 3+ .…”