Direct anabolic metabolism of three-carbon propionate to a six-carbon metabolite occurs in vivo across tissues and species

J Lipid Res. 2022 Jun;63(6):100224. doi: 10.1016/j.jlr.2022.100224. Epub 2022 May 11.


Anabolic metabolism of carbon in mammals is mediated via the one- and two-carbon carriers S-adenosyl methionine and acetyl-coenzyme A. In contrast, anabolic metabolism of three-carbon units via propionate has not been shown to extensively occur. Mammals are primarily thought to oxidize the three-carbon short chain fatty acid propionate by shunting propionyl-CoA to succinyl-CoA for entry into the TCA cycle. Here, we found that this may not be absolute as, in mammals, one nonoxidative fate of propionyl-CoA is to condense to two three-carbon units into a six-carbon trans-2-methyl-2-pentenoyl-CoA (2M2PE-CoA). We confirmed this reaction pathway using purified protein extracts provided limited substrates and verified the product via LC-MS using a synthetic standard. In whole-body in vivo stable isotope tracing following infusion of 13C-labeled valine at steady state, 2M2PE-CoA was found to form via propionyl-CoA in multiple murine tissues, including heart, kidney, and to a lesser degree, in brown adipose tissue, liver, and tibialis anterior muscle. Using ex vivo isotope tracing, we found that 2M2PE-CoA also formed in human myocardial tissue incubated with propionate to a limited extent. While the complete enzymology of this pathway remains to be elucidated, these results confirm the in vivo existence of at least one anabolic three- to six-carbon reaction conserved in humans and mice that utilizes propionate.

Keywords: 2M2PE-CoA; LC-MS/HRMS; Metabolism; TCA cycle; acetyl-CoA; anabolism; condensation reaction; propionate; stable isotope tracing; valine.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural

MeSH terms

  • Acetyl Coenzyme A / metabolism
  • Acyl Coenzyme A / metabolism
  • Animals
  • Carbon* / metabolism
  • Liver / metabolism
  • Mice
  • Oxidation-Reduction
  • Propionates*


  • Acyl Coenzyme A
  • Propionates
  • Acetyl Coenzyme A
  • Carbon