CONTROL OF REVERSIBLE INTRACELLULAR TRANSFER OF REDUCING POTENTIAL
CONTROL OF REVERSIBLE INTRACELLULAR TRANSFER OF REDUCING POTENTIAL
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DOI：
10.1016/0003-9861(91)90260-p
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发表时间：
1991-01-01
影响因子：
3.9
通讯作者：
DAVIS, EJ
中科院分区：
文献类型：
--
作者：
KUNZ, WS;DAVIS, EJ
分离的大鼠肝线粒体中孵育的存在下，重建的苹果酸-天冬氨酸穿梭在羧化条件下，在存在的谷氨酸，辛酰-肉毒碱和丙酮酸，或预设的乳酸/丙酮酸的比例。可溶性F1-ATPase改变了呼吸作用和伴随的能量状态.在这些条件下，由于丙酮酸羧化而输出还原当量。这通过从丙酮酸盐产生乳酸盐和乳酸盐/丙酮酸盐比率的显著增加来显示。这导致了苹果酸输出和能量驱动的苹果酸循环之间的竞争，通过苹果酸-天冬氨酸穿梭，导致线粒体和线粒体外空间之间的NAD系统的氧化还原分离降低。如果丙酮酸羧化被阻断，还原当量的排出也被阻断，导致氧化还原分离的值升高，Δ G氧化还原（kJ）=− 5.7 log（NAD+ NADH输出）/（NAD+ NADH输入）约等于膜电位的一半，与产电谷氨酸/天冬氨酸交换一致。苹果酸-丙酮酸循环的重建导致ΔG氧化还原的原始苹果酸-天冬氨酸穿梭驱动值的进一步动力学降低。因此，由谷氨酸/天冬氨酸交换引起的线粒体和胞质溶胶之间的还原电位分离的值可以通过从线粒体输出还原当量的过程（例如丙酮酸羧化和丙酮酸循环）在动力学上减少。
Isolated rat liver mitochondria were incubated in the presence of a reconstituted malate-aspartate shuttle under carboxylating conditions in the presence of glutamate, octanoyl-carnitine and pyruvate, or a preset lactate/pyruvate ratio. The respiration and attendant energy state were varied with soluble F 1-ATPase. Under these conditions reducing equivalents are exported due to pyruvate carboxylation. This was shown by lactate production from pyruvate and by a substantial increase in the lactate/pyruvate ratio. This led to a competition between malate export and energy-driven malate cycling via the malate-aspartate shuttle, resulting in a lowered redox segregation of the NAD systems between the mitochondrial and extramitochondrial spaces. If pyruvate carboxylation was blocked, this egress of reducing equivalents was also blocked, leading to an elevated value of redox segregation, Δ G redox (in kJ)=− 5.7 log (NAD+ NADH out)/(NAD+ NADH in) being then equal to approximately one-half of the membrane potential, in accordance with electrogenic glutamate/aspartate exchange. Reconstitution of malate-pyruvate cycling led to a further kinetic decrease in the original malate-aspartate shuttle-driven value of ΔG redox. Therefore, the value of segregation of reducing potential between mitochondria and cytosol caused by glutamate/aspartate exchange can be diminished kinetically by processes exporting reducing equivalents from mitochondria, such as pyruvate carboxylation and pyruvate cycling.