Photoinduced Electron Transfer from a 1,4,5,6-Tetrahydro Nicotinamide Adenine Dinucleotide (Phosphate) Analog to Oxidized Flavin in an Ene-Reductase Flavoenzyme

Magnus Speirs, Samantha Hardman, Andreea Iulia Iorgu, Linus Johannissen, Derren Heyes, Nigel Scrutton, Igor V. Sazanovich, Sam Hay

Research output: Contribution to journalArticlepeer-review

Abstract

Recent reports have described the use of ene-reductase flavoenzymes to catalyze non-natural photochemical reactions. These have focused on using reduced flavoenzyme, yet oxidized flavins have superior light harvesting properties. In a binary complex of the oxidized ene-reductase PETNR with the nonreactive nicotinamide coenzyme analogs 1,4,5,6-tetrahydro NAD(P)H, visible photoexcitation of the FMN leads to 1-electron transfer from the NAD(P)H4 to FMN, generating a NAD(P)H4 cation radical and anionic FMN semiquinone. This electron transfer occurs in ~1 ps and appears to kinetically outcompete reductive quenching from aromatic residues in the active site. Time-resolved infrared measurements show that relaxation processes appear to be largely localized on the FMN and the charge-separated state is short-lived, with relaxation, presumably via back electron transfer, occurring over ~3-30 ps. While this demonstrates the potential for non-natural photoactivity, useful photocatalysis will likely require longer-lived excited states, which may be accessible by enzyme engineering and/or judicious choice of substrate.
Original languageEnglish
JournalJournal of Physical Chemistry Letters
Publication statusAccepted/In press - 23 Mar 2023

Keywords

  • time-resolved spectroscopy
  • flavin
  • coenzyme
  • photocatalysis
  • pentaerythritol tetranitrate reductase

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