title: [U-13C]glutamate metabolism in rat brain mitochondria reveals malic enzyme activity.
abstract: 13C nuclear magnetic resonance spectroscopy was used to study the activity of malic enzyme in isolated brain mitochondria from rat in the presence of unlabelled malate and [U-13C]glutamate. ADP, inorganic phosphate, malate and [U-13C]glutamate were added to a suspension of oxygenated mitochondria. Typical tricarboxylic acid (TCA) cycle constituents (malate, 2-oxoglutarate and succinate) were labelled from [U-13C]glutamate and detected in the superfusion medium. The labelling patterns in the different atom positions of glutamate revealed entry of both unlabelled and labelled acetyl-CoA into the TCA cycle. Unlabelled acetyl-CoA was derived via pyruvate from exogenously applied malate by the action of mitochondrial malic enzyme, while labelled acetyl-CoA was derived from TCA cycle intermediates, most likely by the action of mitochondrial malic enzyme on malate produced from [U-13C]glutamate. The results demonstrate malic enzyme activity and pyruvate recycling in isolated rat brain mitochondria.
authors.affiliation: Institute of Physics, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
authors.forename: I J
authors.initials: IJ
authors.lastname: Bakken
authors.forename: U
authors.initials: U
authors.lastname: Sonnewald
authors.forename: J B
authors.initials: JB
authors.lastname: Clark
authors.forename: T E
authors.initials: TE
authors.lastname: Bates
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology / Q000378:metabolism*; D002247:Carbon Isotopes; D018698:Glutamic Acid / Q000378:metabolism*; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy; D008291:Malate Dehydrogenase / Q000378:metabolism*; D008293:Malates / Q000378:metabolism*; D008297:Male; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism*; D011773:Pyruvates / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
chemical_list: D002247:Carbon Isotopes; D008293:Malates; D011773:Pyruvates; D018698:Glutamic Acid; D008291:Malate Dehydrogenase