大鼠脑线粒体中谷氨酸代谢途径。

The pathway of glutamate metabolism in rat brain mitochondria.

作者信息

Dennis S C, Clark J B

出版信息

Biochem J. 1977 Dec 15;168(3):521-7. doi: 10.1042/bj1680521.

DOI:10.1042/bj1680521

PMID:606250

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC1183800/

Abstract

The pathway of glutamate metabolism in non-synaptic rat brain mitochondria was investigated by measuring glutamate, aspartate and ammonia concentrations and oxygen uptakes in mitochondria metabolizing glutamate or glutamine under various conditions. 2. Brain mitochondria metabolizing 10mm-glutamate in the absence of malate produce aspartate at 15nmol/min per mg of protein, but no detectable ammonia. If amino-oxyacetate is added, the aspartate production is decreased by 80% and ammonia production is now observed at a rate of 6.3nmol/min per mg of protein. 3. Brain mitochondria metabolizing glutamate at various concentrations (0-10mm) in the presence of 2.5mm-malate produce aspartate at rates that are almost stoicheiometric with glutamate disappearance, with no detectable ammonia production. In the presence of amino-oxyacetate, although the rate of aspartate production is decreased by 75%, ammonia production is only just detectable (0.3nmol/min per mg of protein). 4. Brain mitochondria metabolizing 10mm-glutamine and 2.5mm-malate in States 3 and 4 were studied by using glutamine as a source of intramitochondrial glutamate without the involvement of mitochondrial translocases. The ammonia production due to the oxidative deamination of glutamate produced from the glutamine was estimated as 1nmol/min per mg of protein in State 3 and 3nmol/min per mg of protein in State 4. 5. Brain mitochondria metabolizing 10mm-glutamine in the presence of 1mm-amino-oxyacetate under State-3 conditions in the presence or absence of 2.5mm-malate showed no detectable aspartate production. In both cases, however, over the first 5min, ammonia production from the oxidative deamination of glutamate was 21-27nmol/min per mg of protein, but then decreased to approx. 1-1.5nmol/min per mg. 6. It is concluded that the oxidative deamination of glutamate by glutamate dehydrogenase is not a major route of metabolism of glutamate from either exogenous or endogenous (glutamine) sources in rat brain mitochondria.

摘要

通过在各种条件下测量代谢谷氨酸或谷氨酰胺的线粒体中谷氨酸、天冬氨酸和氨的浓度以及氧气摄取量，研究了非突触大鼠脑线粒体中谷氨酸的代谢途径。2. 在没有苹果酸的情况下，代谢10 mM谷氨酸的脑线粒体以每毫克蛋白质每分钟15 nmol的速率产生天冬氨酸，但未检测到氨。如果添加氨基氧乙酸，天冬氨酸的产生量减少80%，现在观察到氨的产生速率为每毫克蛋白质每分钟6.3 nmol。3. 在2.5 mM苹果酸存在的情况下，代谢各种浓度（0 - 10 mM）谷氨酸的脑线粒体产生天冬氨酸的速率几乎与谷氨酸的消失化学计量，未检测到氨的产生。在氨基氧乙酸存在的情况下，尽管天冬氨酸的产生速率降低了75%，但氨的产生仅刚刚可检测到（每毫克蛋白质每分钟0.3 nmol）。4. 通过使用谷氨酰胺作为线粒体内谷氨酸的来源而不涉及线粒体转运体，研究了在状态3和状态4下代谢10 mM谷氨酰胺和2.5 mM苹果酸的脑线粒体。由谷氨酰胺产生的谷氨酸氧化脱氨产生的氨估计在状态3下为每毫克蛋白质每分钟1 nmol，在状态4下为每毫克蛋白质每分钟3 nmol。5. 在状态3条件下，在有或没有2.5 mM苹果酸存在的情况下，在1 mM氨基氧乙酸存在下代谢10 mM谷氨酰胺的脑线粒体未检测到天冬氨酸的产生。然而，在这两种情况下，在最初的5分钟内，谷氨酸氧化脱氨产生的氨为每毫克蛋白质每分钟21 - 27 nmol，但随后降至约每毫克蛋白质每分钟1 - 1.5 nmol。6. 得出的结论是，谷氨酸脱氢酶对谷氨酸的氧化脱氨不是大鼠脑线粒体中外源或内源性（谷氨酰胺）来源的谷氨酸代谢的主要途径。