title: Metabolism of propionic acid to a novel acyl-coenzyme A thioester by mammalian cell lines and platelets.
abstract: Metabolism of propionate involves the activated acyl-thioester propionyl-CoA intermediate. We employed LC-MS/MS, LC-selected reaction monitoring/MS, and LC-high-resolution MS to investigate metabolism of propionate to acyl-CoA intermediates. We discovered that propionyl-CoA can serve as a precursor to the direct formation of a new six-carbon mono-unsaturated acyl-CoA. Time course and dose-response studies in human hepatocellular carcinoma HepG2 cells demonstrated that the six-carbon mono-unsaturated acyl-CoA was propionate-dependent and underwent further metabolism over time. Studies utilizing [(13)C1]propionate and [(13)C3]propionate suggested a mechanism of fatty acid synthesis, which maintained all six-carbon atoms from two propionate molecules. Metabolism of 2,2-[(2)H2]propionate to the new six-carbon mono-unsaturated acyl-CoA resulted in the complete loss of two deuterium atoms, indicating modification at C2 of the propionyl moiety. Coelution experiments and isotopic tracer studies confirmed that the new acyl-CoA was trans-2-methyl-2-pentenoyl-CoA. Acyl-CoA profiles following treatment of HepG2 cells with mono-unsaturated six-carbon fatty acids also supported this conclusion. Similar results were obtained with human platelets, mouse hepatocellular carcinoma Hepa1c1c7 cells, human bronchoalveolar carcinoma H358 cells, and human colon adenocarcinoma LoVo cells. Interestingly, trans-2-methyl-2-pentenoyl-CoA corresponds to a previously described acylcarnitine tentatively described in patients with propionic and methylmalonic acidemia. We have proposed a mechanism for this metabolic route consistent with all of the above findings.
authors.affiliation: Department of Systems Pharmacology and Translational Therapeutics, University of Pennsylvania, Philadelphia, PA 19104 A. J. Drexel Autism Institute, Drexel University, Philadelphia, PA 19104.
authors.forename: Nathaniel W
authors.initials: NW
authors.lastname: Snyder
authors.affiliation: Department of Systems Pharmacology and Translational Therapeutics, University of Pennsylvania, Philadelphia, PA 19104.
authors.forename: Sankha S
authors.initials: SS
authors.lastname: Basu
authors.affiliation: Department of Systems Pharmacology and Translational Therapeutics, University of Pennsylvania, Philadelphia, PA 19104.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Worth
authors.affiliation: Department of Systems Pharmacology and Translational Therapeutics, University of Pennsylvania, Philadelphia, PA 19104.
authors.forename: Clementina
authors.initials: C
authors.lastname: Mesaros
authors.affiliation: Department of Systems Pharmacology and Translational Therapeutics, University of Pennsylvania, Philadelphia, PA 19104.
authors.forename: Ian A
authors.initials: IA
authors.lastname: Blair
mesh_terms: D000214:Acyl Coenzyme A / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D002460:Cell Line; D006801:Humans; D007553:Isotope Labeling; D051379:Mice; D011422:Propionates / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013997:Time Factors
chemical_list: D000214:Acyl Coenzyme A; D011422:Propionates; D013438:Sulfhydryl Compounds; C029658:propionic acid
keywords: 2-methyl-2-pentenoic acid; mass spectrometry; propionic acidemia; stable isotope labeling by essential nutrients in cell culture; stable isotopes