Porter J W, Swenson T L
Mol Cell Biochem. 1983;53-54(1-2):307-25. doi: 10.1007/BF00225262.
Current studies on the synthesis of long-chain fatty acids by isolated rat liver cells are largely concerned with the regulation of the activity of previously existing acetyl-CoA carboxylase and fatty acid synthetase, and with the regulation of the quantity of these enzymes. These studies have required the development of methods for obtaining high yields of viable hepatocytes that respond to hormonal treatment. Such methods have been developed over the past 10-15 years through the efforts of several laboratories. These studies have also required the development of a method to determine whether a change in the activity of an enzyme is due to a modification of preexisting enzyme or to a change in quantity of that enzyme. The most satisfactory method to use for such studies is immunotitration of enzyme activity. In recent years studies on the regulation of acetyl-CoA carboxylase have largely centered upon the effect of phosphorylation-dephosphorylation on the activity of this enzyme and whether glucagon inhibits the activity of this enzyme through this process. Much data from a number of laboratories have suggested that glucagon regulates the activity of this enzyme through phosphorylation-dephosphorylation. However, several of these studies involved the use of crude systems in which competing enzymes and substrates that can significantly interfere with acetyl-CoA carboxylase activity measurements were still present. Hence, a confirmation of these studies needs to be carried out under conditions in which the effects of competing enzymes and substrates are eliminated. Studies on changes in quantity of acetyl-CoA carboxylase and fatty acid synthetase have shown that these enzymes are induced by the fasting and refeeding of animals. They have also shown that insulin stimulates (10- to 30-fold) the induction of these enzymes. This induction appears to be due to a change in the quantity of translatable mRNA which may, in turn, be due to a change in the rate of transcription of the genes coding for these enzymes.
目前关于分离的大鼠肝细胞合成长链脂肪酸的研究，主要关注于对先前存在的乙酰辅酶A羧化酶和脂肪酸合成酶活性的调节，以及对这些酶数量的调节。这些研究需要开发出能够获得高产量且对激素处理有反应的活肝细胞的方法。在过去10到15年里，通过几个实验室的努力，这样的方法已经被开发出来。这些研究还需要开发一种方法来确定酶活性的变化是由于预先存在的酶的修饰，还是由于该酶数量的变化。用于此类研究的最令人满意的方法是酶活性的免疫滴定法。近年来，关于乙酰辅酶A羧化酶调节的研究主要集中在磷酸化-去磷酸化对该酶活性的影响，以及胰高血糖素是否通过这个过程抑制该酶的活性。来自许多实验室的大量数据表明，胰高血糖素通过磷酸化-去磷酸化来调节该酶的活性。然而，这些研究中有几项涉及使用粗制系统，其中仍然存在能够显著干扰乙酰辅酶A羧化酶活性测量的竞争性酶和底物。因此，需要在消除竞争性酶和底物影响的条件下对这些研究进行验证。关于乙酰辅酶A羧化酶和脂肪酸合成酶数量变化的研究表明，这些酶是由动物禁食和重新喂食诱导产生的。研究还表明，胰岛素刺激（10至30倍）这些酶的诱导产生。这种诱导似乎是由于可翻译mRNA数量的变化，而这反过来可能是由于编码这些酶的基因转录速率的变化。
