Fukuda H, Katsurada A, Iritani N
Biochim Biophys Acta. 1985 Jul 9;835(2):163-8. doi: 10.1016/0005-2760(85)90269-3.
The activities of glucose-6-phosphate dehydrogenase, malic enzyme, fatty acid synthetase and acetyl-CoA carboxylase (extracted with or without phosphatase inhibitor) in rat liver did not vary significantly during 24 h. The hepatic levels of glucose 6-phosphate and malate increased coordinately 3-6 h after the beginning (1900 h) of food intake and were high until morning, whereas the levels of acetyl-CoA and citrate peaked at 1900 h and then decreased. However, it is remarkable that the in vivo incorporation of 3H from tritiated water into fatty acids in liver increased with the level of malonyl-CoA after food intake. Comparing the substrate and effector levels with the Km and Ka values for the enzymes, the levels of acetyl-CoA, malonyl-CoA and citrate appear to limit the enzyme activities. It is suggested that, after food intake, the physiological activity of acetyl-CoA carboxylase was increased with the substrate increase and/or with the catalytic activation with citrate, and consequently, the fatty acid synthetase activity was also increased, whereas the enzyme activities measured under optimum conditions were not.
大鼠肝脏中葡萄糖-6-磷酸脱氢酶、苹果酸酶、脂肪酸合成酶和乙酰辅酶A羧化酶（无论是否用磷酸酶抑制剂提取）的活性在24小时内无显著变化。进食开始（1900时）后3 - 6小时，肝内葡萄糖6-磷酸和苹果酸水平协同升高，并一直维持在较高水平直至早晨，而乙酰辅酶A和柠檬酸水平在1900时达到峰值后下降。然而，值得注意的是，进食后肝脏中从氚水掺入脂肪酸的3H体内掺入量随丙二酰辅酶A水平升高而增加。将底物和效应物水平与酶的Km和Ka值进行比较，乙酰辅酶A、丙二酰辅酶A和柠檬酸水平似乎限制了酶的活性。这表明，进食后，乙酰辅酶A羧化酶的生理活性随着底物增加和/或柠檬酸的催化激活而增加，因此脂肪酸合成酶活性也增加，而在最佳条件下测得的酶活性则没有增加。
