title: Determination of R- and S-3-methyl-2-oxopentanoate enantiomers in human plasma: suitable method for label enrichment analysis.
abstract: A sensitive method for the determination of S- and R-3-methyl-2-oxopentanoate enantiomers (KMV, alpha-keto-beta-methylvalerate) in physiological fluids suitable for isotope enrichment analysis is described: after extraction with acid, 2-oxo acids are separated from interfering amino acids by cation-exchange chromatography. Reductive amination of the branched-chain 2-oxo acids by use of L-leucine dehydrogenase yields the corresponding L-amino acids. L-Isoleucine and L-alloisoleucine which are formed from S- and R-3-methyl-2-oxopentanoate, respectively, are then quantified by amino acid analysis. The method was used for determination of the R-IS-3-methyl-2-oxopentanoate ratio in plasma of healthy subjects and patients with diabetes mellitus and maple syrup urine disease. Applicability for gas chromatographic-mass spectrometric analysis of 13C-label enrichment in plasma S-3-methyl-2-oxopentanoate is demonstrated.
authors.affiliation: Diabetes Forschungsinstitut, Heinrich-Heine-Universität, Düsseldorf, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Schadewaldt
authors.forename: U
authors.initials: U
authors.lastname: Wendel
authors.forename: H W
authors.initials: HW
authors.lastname: Hammen
mesh_terms: D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007651:Keto Acids / Q000097:blood* / Q000737:chemistry; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013237:Stereoisomerism
chemical_list: D007651:Keto Acids; C016211:alpha-keto-beta-methylvaleric acid