Mohan C, Bessman S P
Arch Biochem Biophys. 1986 Jul;248(1):190-9. doi: 10.1016/0003-9861(86)90416-9.
It has long been known that the carbons of pyruvate are converted to CO2 at different points in the metabolic process. This report deals with the observation that insulin affects the oxidation of carbons 2 and 3 primarily and has little effect on the oxidation of the carboxyl carbon. Oxidation of different carbons of pyruvate and their incorporation into various metabolic components was studied in isolated rat hepatocytes. Insulin stimulated the 14CO2 production from [2-14C]- and [3-14C]pyruvate and from [U-14C]alanine. However, it had little or no effect on the activity of the pyruvate dehydrogenase complex as measured by the evolution of 14CO2 from [1-14C]pyruvate or [1-14C] alanine. Insulin also stimulated the incorporation of carbons 2 and 3 of pyruvate into protein but had no effect on the incorporation of carbon 1. Incorporation of [1-14C]- and [U-14C]alanine into protein was differentially enhanced by insulin in a manner similar to that of the pyruvate carbons. The fact that insulin stimulates the incorporation of [1-14C]alanine into protein but not [1-14C]pyruvate suggests the possibility of a compartmentation of pyruvate metabolism in the isolated hepatocytes. These studies show that the stimulation of [2-14C]- and [3-14C]pyruvate incorporation into protein involves the stimulatory effect of insulin on the activity of the Krebs cycle which is evident from the fact that insulin did not stimulate the pyruvate carbons to enter protein via alanine but the incorporation via glutamate was increased by about 40%.
长期以来，人们都知道丙酮酸的碳原子在代谢过程的不同点会转化为二氧化碳。本报告涉及一项观察结果，即胰岛素主要影响碳原子2和3的氧化，而对羧基碳的氧化影响很小。在分离的大鼠肝细胞中研究了丙酮酸不同碳原子的氧化及其掺入各种代谢成分的情况。胰岛素刺激了[2-¹⁴C]-和[3-¹⁴C]丙酮酸以及[U-¹⁴C]丙氨酸生成¹⁴CO₂。然而，通过[1-¹⁴C]丙酮酸或[1-¹⁴C]丙氨酸释放¹⁴CO₂来测量，胰岛素对丙酮酸脱氢酶复合体的活性几乎没有影响。胰岛素还刺激了丙酮酸的碳原子2和3掺入蛋白质，但对碳原子1的掺入没有影响。胰岛素以与丙酮酸碳原子类似的方式差异性地增强了[1-¹⁴C]-和[U-¹⁴C]丙氨酸掺入蛋白质的过程。胰岛素刺激[1-¹⁴C]丙氨酸掺入蛋白质而不刺激[1-¹⁴C]丙酮酸掺入蛋白质这一事实表明，在分离的肝细胞中丙酮酸代谢可能存在区室化。这些研究表明，[2-¹⁴C]-和[3-¹⁴C]丙酮酸掺入蛋白质的刺激作用涉及胰岛素对三羧酸循环活性的刺激作用，这从以下事实可以明显看出：胰岛素并未刺激丙酮酸碳原子通过丙氨酸进入蛋白质，但通过谷氨酸的掺入增加了约40%。
