Metabolic annotation of 2-ethylhydracrylic acid.

Abstract

Increased levels of the organic acid, 2-ethylhydracrylic acid (2-EHA) occur in urine of subjects with impaired L(+)-isoleucine metabolism. Chiral intermediates formed during isoleucine degradation are (S) enantiomers. Blockage of (S) pathway flux drives racemization of (2S, 3S) L(+)-isoleucine and its (2S, 3R) stereoisomer, L(+)-alloisoleucine. This non-protein amino acid is metabolized to (R)-2-methylbutyryl CoA via enzymes common to branched chain amino acid degradation. Subsequently, (R) intermediates serve as alternate substrates for three valine metabolic enzymes, generating 2-EHA. Once formed, 2-EHA accumulates because it is poorly recognized by distal valine pathway enzymes. Thus, urinary 2-EHA represents a biomarker of isoleucine pathway defects. 2-EHA levels are also increased in rats exposed to the industrial solvent, ethylene glycol monomethyl ether or the neurotoxin precursor, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. In these cases, a block in (S) pathway isoleucine catabolism occurs at the level of (S)-2-methylbutyryl CoA conversion to tiglyl CoA via inhibition of electron transferring flavoprotein/ubiquinone oxidoreductase dependent reactions. Elevated urinary 2-EHA in propionyl CoA carboxylase deficiency and methylmalonic aciduria results from a buildup of distal intermediates in the (S) pathway of isoleucine degradation. In Barth syndrome and dilated cardiomyopathy with ataxia syndrome, 2-EHA is a byproduct of impeded propionyl CoA entry into the Krebs cycle.

• Authors: Robert O Ryan
• Journal: Clinica chimica acta; international journal of clinical chemistry (Clin Chim Acta) Vol. 448 Pg. 91-7 (Aug 25 2015) ISSN: 1873-3492 [Electronic] Netherlands
• PMID: 26115894 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Review)
• Copyright: Copyright © 2015 Elsevier B.V. All rights reserved.

Chemical References

• Valerates
• 2-ethylhydracrylic acid

Topics

• Animals
• Barth Syndrome (metabolism)
• Humans
• Multiple Acyl Coenzyme A Dehydrogenase Deficiency (metabolism)
• Valerates (metabolism)