title: Measurement of the turnover of glycogen phosphorylase by GC/MS using stable isotope derivatives of pyridoxine (vitamin B6).
abstract: The majority of vitamin B6 in the body is in skeletal muscle, bound as the cofactor pyridoxal 5'-phosphate to one abundant protein, glycogen phosphorylase. Previous work has established that radiolabelled vitamin B6 can be used as a turnover label for glycogen phosphorylase. In this study, a stable isotope derivative of pyridoxine {dideuterated pyridoxine; 3-hydroxy-4-(hydroxymethyl) -5-[hydroxymethyl-2H2]-2-methylpyridine} ([2H2]PN) has been used as a metabolic tracer to study the kinetics of labelling of the body pools of vitamin B6 in mice. A non-invasive method was developed in which the isotope abundance of the urinary excretory product of vitamin B6 metabolism, 4-pyridoxic acid, was analysed by GC/MS. The change in isotope abundance of urinary 4-pyridoxic acid following administration of [2H2]PN reflects the kinetics of labelling of the body pools of vitamin B6, and yields, non-invasively, the rate of degradation of glycogen phosphorylase.
authors.affiliation: Department of Biochemistry and Applied Molecular Biology, UMIST, Manchester, U.K.
authors.forename: R J
authors.initials: RJ
authors.lastname: Beynon
authors.forename: D M
authors.initials: DM
authors.lastname: Leyland
authors.forename: R P
authors.initials: RP
authors.lastname: Evershed
authors.forename: R H
authors.initials: RH
authors.lastname: Edwards
authors.forename: S P
authors.initials: SP
authors.lastname: Coburn
mesh_terms: D000818:Animals; D001825:Body Fluid Compartments; D003903:Deuterium; D008401:Gas Chromatography-Mass Spectrometry; D007700:Kinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000201:enzymology / Q000378:metabolism*; D006005:Phosphorylases / Q000378:metabolism*; D010827:Physiology / Q000379:methods; D011735:Pyridoxic Acid / Q000652:urine*; D011736:Pyridoxine / Q000031:analogs & derivatives / Q000378:metabolism*
chemical_list: D011735:Pyridoxic Acid; D003903:Deuterium; D006005:Phosphorylases; D011736:Pyridoxine