Abstract
Firefly D-luciferin, the specific substrate for the bioluminescence reaction, has the same chirality, with a stereogenic centre, as unnatural D-cysteine. The enantiomer L-luciferin has the same chirality as natural L-cysteine, and behaves as a competitive luciferase inhibitor, as do dehydroluciferin, fatty acids. Firefly luciferase was able to convert L-luciferin into luciferyl-CoA even under ordinary aerobic luciferin-luciferase reaction conditions. D-Luciferin inhibited the luciferyl-CoA synthetase activity of L-luciferin, whereas L-luciferin retards the bioluminescence reaction of D-luciferin, meaning that both enzyme activities are prevented by the enantiomer of its own substrate. It is anticipated that luciferyl-CoA was easily epimerized at neutral pH. Therefore L-luciferin can be converted into D-luciferin by firefly luciferase, an esterase, ATP, Mg^<2+>, and CoA. Because L-luciferin was converted luciferyl-CoA by firefly luciferase, and then epimerized luciferyl-CoA was hydrolysis by esterase to yield D- and L-luciferin. Whereas the regenerated L-luciferin would be rapidly re-converted to luciferyl-CoA, D-luciferin could be used for the light-producing reaction. We have identified a novel route of D-luciferin formation from L-luciferin in vitro that allows the construction of a new firefly bioluminescence system using L-luciferin.
