Lenartowicz E, Wojtczak A B
Department of Cellular Biochemistry, Nencki Institute of Experimental Biology, Warsaw, Poland.
Arch Biochem Biophys. 1988 Jan;260(1):309-19. doi: 10.1016/0003-9861(88)90455-9.
The total production of alpha-ketoglutarate from glutamate and isocitrate was estimated in isolated rat liver mitochondria. Mitochondrial alanine aminotransferase converts glutamate to alpha-ketoglutarate [A.K. Groen et al. (1982) Eur. J. Biochem. 122, 87-93], thus participating in the net formation of the tricarboxylic acid cycle intermediates from glutamate. The present investigation indicates a significant contribution of the alanine aminotransferase reaction to glutamate oxidation by isolated rat liver mitochondria in the presence of bicarbonate. It amounted to 41-74 and 7-31% of the total utilization of glutamate in States 4 and 3, respectively, in various conditions in vitro, at pyruvate concentrations in the range of 0.1-10 mM. The participation of glutamate in the total production of alpha-ketoglutarate at physiological concentrations of glutamate, citrate, and isocitrate varied in the range of 72-82%. It was calculated that alpha-ketoglutarate formation by the reaction of alanine aminotransferase amounted to 30 and 5% of the total mitochondrial alpha-ketoglutarate production in States 4 and 3, respectively, at physiological concentrations of its precursors and in the presence of 0.5 mM malate and 0.1 mM pyruvate. It constituted 77-97% of the net production of the tricarboxylic acid cycle intermediates from glutamate in rat liver mitochondria. The importance of alpha-ketoglutarate production via the alanine aminotransferase reaction under various physiological conditions is discussed.
在分离的大鼠肝脏线粒体中估计了由谷氨酸和异柠檬酸生成α-酮戊二酸的总量。线粒体丙氨酸转氨酶将谷氨酸转化为α-酮戊二酸[A.K.格伦等人（1982年），《欧洲生物化学杂志》122卷，87 - 93页]，从而参与了从谷氨酸净生成三羧酸循环中间体的过程。本研究表明，在存在碳酸氢盐的情况下，丙氨酸转氨酶反应对分离的大鼠肝脏线粒体氧化谷氨酸有显著贡献。在体外不同条件下，丙酮酸浓度在0.1 - 10 mM范围内时，该反应分别占状态4和状态3下谷氨酸总利用率的41 - 74%和7 - 31%。在谷氨酸、柠檬酸和异柠檬酸的生理浓度下，谷氨酸对α-酮戊二酸总生成量的贡献在72 - 82%范围内变化。据计算，在其前体的生理浓度以及存在0.5 mM苹果酸和0.1 mM丙酮酸的情况下，丙氨酸转氨酶反应生成的α-酮戊二酸分别占状态4和状态3下线粒体α-酮戊二酸总生成量的30%和5%。它占大鼠肝脏线粒体中从谷氨酸净生成三羧酸循环中间体的77 - 97%。本文讨论了在各种生理条件下通过丙氨酸转氨酶反应生成α-酮戊二酸的重要性。
