title: Stereochemistry of the peroxisomal branched-chain fatty acid alpha- and beta-oxidation systems in patients suffering from different peroxisomal disorders.
abstract: Phytanic acid (3,7,11,15-tetramethylhexadecanoic acid) is a branched-chain fatty acid derived from dietary sources and broken down in the peroxisome to pristanic acid (2,6,10,14-tetramethylpentadecanoic acid) via alpha-oxidation. Pristanic acid then undergoes beta-oxidation in peroxisomes. Phytanic acid naturally occurs as a mixture of (3S,7R,11R)- and (3R,7R,11R)-diastereomers. In contrast to the alpha-oxidation system, peroxisomal beta-oxidation is stereospecific and only accepts (2S)-isomers. Therefore, a racemase called alpha-methylacyl-CoA racemase is required to convert (2R)-pristanic acid into its (2S)-isomer. To further investigate the stereochemistry of the peroxisomal oxidation systems and their substrates, we have developed a method using gas-liquid chromatography-mass spectrometry to analyze the isomers of phytanic, pristanic, and trimethylundecanoic acid in plasma from patients with various peroxisomal fatty acid oxidation defects. In this study, we show that in plasma of patients with a peroxisomal beta-oxidation deficiency, the relative amounts of the two diastereomers of pristanic acid are almost equal, whereas in patients with a defect of alpha-methylacyl-CoA racemase, (2R)-pristanic acid is the predominant isomer. Furthermore, we show that in alpha-methylacyl-CoA racemase deficiency, not only pristanic acid accumulates, but also one of the metabolites of pristanic acid, 2610-trimethylundecanoic acid, providing direct in vivo evidence for the requirement of this racemase for the complete degradation of pristanic acid.
authors.affiliation: University of Amsterdam, Academic Medical Center, Department of Clinical Chemistry, Amsterdam, The Netherlands.
authors.forename: S
authors.initials: S
authors.lastname: Ferdinandusse
authors.forename: H
authors.initials: H
authors.lastname: Rusch
authors.forename: A E M
authors.initials: AE
authors.lastname: van Lint
authors.forename: G
authors.initials: G
authors.lastname: Dacremont
authors.forename: R J A
authors.initials: RJ
authors.lastname: Wanders
authors.forename: P
authors.initials: P
authors.lastname: Vreken
mesh_terms: D005227:Fatty Acids / Q000097:blood / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D006899:Mixed Function Oxygenases / Q000172:deficiency / Q000378:metabolism*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000172:deficiency / Q000378:metabolism*; D018901:Peroxisomal Disorders / Q000097:blood / Q000201:enzymology / Q000378:metabolism*; D010831:Phytanic Acid / Q000097:blood / Q000737:chemistry / Q000378:metabolism*; D019998:Racemases and Epimerases / Q000172:deficiency / Q000378:metabolism*; D012035:Refsum Disease / Q000097:blood / Q000201:enzymology / Q000378:metabolism; D013237:Stereoisomerism
chemical_list: D005227:Fatty Acids; D010831:Phytanic Acid; C002844:pristanic acid; D006899:Mixed Function Oxygenases; D010088:Oxidoreductases; C102623:PHYH protein, human; C081094:branched chain acyl-CoA oxidase; D019998:Racemases and Epimerases; C108352:alpha-methylacyl-CoA racemase