Ethylmalonyl-CoA Mutase From Rhodobacter Sphaeroides Defines a New Subclade of Coenzyme B12-dependent acyl-CoA Mutases

J Biol Chem. 2008 Nov 21;283(47):32283-93. doi: 10.1074/jbc.M805527200. Epub 2008 Sep 25.


Coenzyme B(12)-dependent mutases are radical enzymes that catalyze reversible carbon skeleton rearrangement reactions. Here we describe Rhodobacter sphaeroides ethylmalonyl-CoA mutase (Ecm), a novel member of the family of coenzyme B(12)-dependent acyl-CoA mutases, that operates in the recently discovered ethylmalonyl-CoA pathway for acetate assimilation. Ecm is involved in the central reaction sequence of this novel pathway and catalyzes the transformation of ethylmalonyl-CoA to methylsuccinyl-CoA in combination with a second enzyme that was further identified as promiscuous ethylmalonyl-CoA/methylmalonyl-CoA epimerase. In contrast to the epimerase, Ecm is highly specific for its substrate, ethylmalonyl-CoA, and accepts methylmalonyl-CoA only at 0.2% relative activity. Sequence analysis revealed that Ecm is distinct from (2R)-methylmalonyl-CoA mutase as well as isobutyryl-CoA mutase and defines a new subfamily of coenzyme B(12)-dependent acyl-CoA mutases. In combination with molecular modeling, two signature sequences were identified that presumably contribute to the substrate specificity of these enzymes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acyl Coenzyme A / chemistry*
  • Cloning, Molecular
  • Cobamides / chemistry*
  • Escherichia coli / genetics
  • Intramolecular Transferases / chemistry*
  • Intramolecular Transferases / physiology
  • Isomerases / chemistry*
  • Magnetic Resonance Spectroscopy
  • Models, Biological
  • Models, Chemical
  • Phenotype
  • Phylogeny
  • Recombinant Proteins / chemistry
  • Rhodobacter sphaeroides / metabolism*
  • Software
  • Substrate Specificity
  • Time Factors


  • Acyl Coenzyme A
  • Cobamides
  • Recombinant Proteins
  • ethylmalonyl-coenzyme A
  • Isomerases
  • Intramolecular Transferases
  • ethylmalonyl-CoA mutase, Rhodobacter sphaeroides
  • cobamamide