β‐Deuterium Isotope Effects on Firefly Luciferase Bioluminescence

A 5,5‐d2‐luciferin was prepared to measure isotope effects on reactions of two intermediates in firefly bioluminescence: emission by oxyluciferin and elimination of a putative luciferyl adenylate hydroperoxide to dehydroluciferin. A negligible isotope effect on bioluminescence provides further suppo...

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Bibliographic Details
Published in:ChemistryOpen (Weinheim) 2017-12, Vol.6 (6), p.697-700
Main Authors: Pirrung, Michael C., Dorsey, Allyson, Howitt, Natalie De, Liao, Jiayu
Format: Article
Language:English
Subjects:
Bioluminescence
Communication
Communications
Deuterium
electron transfer
elimination
Isotope effect
isotope effects
Isotopes
luminescence
tautomerization
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Summary:A 5,5‐d2‐luciferin was prepared to measure isotope effects on reactions of two intermediates in firefly bioluminescence: emission by oxyluciferin and elimination of a putative luciferyl adenylate hydroperoxide to dehydroluciferin. A negligible isotope effect on bioluminescence provides further support for the belief that the emitting species is the keto‐phenolate of oxyluciferin and rules out its excited‐state tautomerization, one potential contribution to a bioluminescence quantum yield less than unity. A small isotope effect on dehydroluciferin formation supports a single‐electron‐transfer mechanism for reaction of the luciferyl adenylate enolate with oxygen to form the hydroperoxide or dehydroluciferin. Partitioning between the dioxetanone intermediate (en route to oxyluciferin) and dehydroluciferin is determined, not by the fate of the hydroperoxide, but by that of the radical formed from luciferyl adenylate, and the kinetic isotope effect (KIE) reflects H‐atom ion by superoxide. Product inhibition: Firefly flashing can be attributed to inhibitory products of the luciferase enzyme. A small isotope effect on the formation of one important product, dehydroluciferin, has mechanistic implications for bioluminescence production.
ISSN:2191-1363
2191-1363
DOI:10.1002/open.201700136