METABOLIC REGULATION OF RAT HEPATIC FLUX OF ISOPRENOIDS

这项提案的主要目标是研究第一种特定的酶 在肝脏的胆固醇生物合成途径中， 合成酶，以了解其调节机制。 这一目标现在可以实现，因为我们最近分离、纯化和 获得了大鼠肝角鲨烯合成酶的部分蛋白质序列， 蛋白质以及大鼠和人酶的cDNA克隆。 反过来，这将使我们能够克隆和研究基因的调控。 酵素 大鼠肝角鲨烯合成酶的调控机制 转录、翻译和蛋白质水平将在广泛的 胆固醇生成的变化。 的变化的贡献 这种酶的活性对普通中间体的转移， 特别是反式焦磷酸法呢酯转化为甾醇和非甾醇 产品（通量转移假设）将被检查。 角鲨烯5 '侧翼区的检测和比较 合成酶基因与该途径中其它已知调节酶的相互作用可以 解释甲羟戊酸分支通路的复杂调节。 角鲨烯合成酶基因的克隆及其调控机制的研究， 胆固醇生物合成途径中最特异的酶， 允许化合物的发展， 这种酶活性，因此可以作为胆固醇 降低药物。

The main objective of this proposal is to study the first specific enzyme in the cholesterol biosynthetic pathway in the liver, squalene synthetase, in order to understand the mechanisms of its regulation. This objective is now attainable since we recently isolated, purified and obtained partial protein sequences of the rat liver squalene synthetase protein as well as cDNA clones for both the rat and the human enzymes. This, in turn, will enable us to clone and study the regulation of the enzyme. The mechanisms of regulation of rat hepatic squalene synthetase at the transcription, translation and protein level will be examined under wide variations of cholesterogenesis. The contribution of the variations of the activity of this enzyme to the diversion of common intermediates, specifically trans-farnesyl pyrophosphate, to sterol and nonsterol products (the flux diversion hypothesis) will be examined. Examination and comparison of 5'flanking regions of the squalene synthetase gene to other known regulatory enzymes in this pathway may explain the complex regulation of the mevalonate branched pathway. Cloning and the understanding of the regulation of squalene synthetase, the most specific enzyme in the cholesterol biosynthetic pathway, may allow the development of compounds that will interact with, and change the activity of this enzyme and therefore, may serve as cholesterol lowering drugs.