One-carbon chemistry of oxalate oxidoreductase captured by X-ray crystallography

Proc Natl Acad Sci U S A. 2016 Jan 12;113(2):320-5. doi: 10.1073/pnas.1518537113. Epub 2015 Dec 28.

Abstract

Thiamine pyrophosphate (TPP)-dependent oxalate oxidoreductase (OOR) metabolizes oxalate, generating two molecules of CO2 and two low-potential electrons, thus providing both the carbon and reducing equivalents for operation of the Wood-Ljungdahl pathway of acetogenesis. Here we present structures of OOR in which two different reaction intermediate bound states have been trapped: the covalent adducts between TPP and oxalate and between TPP and CO2. These structures, along with the previously determined structure of substrate-free OOR, allow us to visualize how active site rearrangements can drive catalysis. Our results suggest that OOR operates via a bait-and-switch mechanism, attracting substrate into the active site through the presence of positively charged and polar residues, and then altering the electrostatic environment through loop and side chain movements to drive catalysis. This simple but elegant mechanism explains how oxalate, a molecule that humans and most animals cannot break down, can be used for growth by acetogenic bacteria.

Keywords: carbon dioxide; oxalate; oxidoreductase; thiamine pyrophosphate.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Carbon / metabolism*
  • Catalytic Domain
  • Crystallography, X-Ray
  • Models, Molecular
  • Moorella / enzymology*
  • Oxalates / metabolism
  • Oxidation-Reduction
  • Oxidoreductases / chemistry
  • Oxidoreductases / metabolism*
  • Protein Structure, Tertiary
  • Solvents

Substances

  • Oxalates
  • Solvents
  • Carbon
  • Oxidoreductases

Associated data

  • PDB/5EXD
  • PDB/5EXE