完整大鼠肝脏线粒体中的柠檬酸合成是不可逆的。

Citrate synthesis in intact rat-liver mitochondria is irreversible.

作者信息

Greksák M, Lopes-Cardozo M, van den Bergh S G

出版信息

Eur J Biochem. 1982 Feb;122(2):423-7. doi: 10.1111/j.1432-1033.1982.tb05897.x.

DOI:10.1111/j.1432-1033.1982.tb05897.x

Abstract

Rat-liver mitochondria were incubated with [1,5-14C]citrate in the presence of fluorocitrate to block its oxidation in the Krebs cycle. The reaction products were analysed enzymatically and by anion-exchange chromatography. Incorporation of 14C into acetyl-L-carnitine or ketone bodies via a backward action of citrate synthase was not observed. The optimal rate of citrate synthesis from pyruvate and malate in the presence of fluorocitrate was 15 nmol . mg-1 min-1. In the absence of fluorocitrate, but in the presence of malonate, citrate was oxidized to succinate at a rate of 4 nmol . mg-1 . min-1. We conclude that the synthesis of citrate by intact rat liver mitochondria is an irreversible process. The possible mechanism underlying this phenomenon and the consequence for metabolic regulation are discussed.

摘要

在氟柠檬酸存在的情况下，将大鼠肝脏线粒体与[1,5-¹⁴C]柠檬酸一起孵育，以阻断其在三羧酸循环中的氧化。通过酶促反应和阴离子交换色谱法对反应产物进行分析。未观察到通过柠檬酸合酶的逆向作用将¹⁴C掺入乙酰-L-肉碱或酮体中。在氟柠檬酸存在的情况下，丙酮酸和苹果酸合成柠檬酸的最佳速率为15 nmol·mg⁻¹·min⁻¹。在不存在氟柠檬酸但存在丙二酸的情况下，柠檬酸以4 nmol·mg⁻¹·min⁻¹的速率氧化为琥珀酸。我们得出结论，完整的大鼠肝脏线粒体合成柠檬酸是一个不可逆的过程。讨论了这一现象背后可能的机制及其对代谢调节的影响。