Enhanced Rigidification within a Double Mutant of Soybean Lipoxygenase Provides Experimental Support for Vibronically Nonadiabatic Proton-Coupled Electron Transfer Models

Shenshen Hu, Alexander V. Soudackov, Sharon Hammes-Schiffer, Judith P. Klinman

Research output: Contribution to journalArticlepeer-review

Abstract

Soybean lipoxygenase (SLO) is a prototype for nonadiabatic hydrogen tunneling reactions and, as such, has served as the subject of numerous theoretical studies. In this work, we report a nearly temperature-independent kinetic isotope effect (KIE) with an average KIE value of 661 ± 27 for a double mutant (DM) of SLO at six temperatures. The data are well-reproduced within a vibronically nonadiabatic proton-coupled electron transfer model in which the active site has become rigidified compared to wild-type enzyme and single-site mutants. A combined temperature-pressure perturbation further shows that temperature-dependent global motions within DM-SLO are more resistant to perturbation by elevated pressure. These findings provide strong experimental support for the model of hydrogen tunneling in SLO, where optimization of both local protein and ligand motions and distal conformational rearrangements is a prerequisite for effective proton vibrational wave function overlap between the substrate and the active-site iron cofactor.

Original languageEnglish (US)
Pages (from-to)3569-3574
Number of pages6
JournalACS Catalysis
Volume7
Issue number5
DOIs
StatePublished - May 5 2017

Keywords

  • biocatalysis
  • conformational sampling
  • hydrogen tunneling
  • kinetic isotope effects
  • nonadiabatic
  • protein motions
  • proton-coupled electron transfer
  • soybean lipoxygenase

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

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