标题：In vivo regulation of rat liver 3-hydroxy-3-methylglutaryl-coenzyme A reductase: immunotitration of the enzyme after short-term mevalonate or cholesterol feeding
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1982
卷号：79
期号：1
页码：51-55
DOI：10.1073/pnas.79.1.51
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：In recent studies using either a single dose of mevalonolactone administered by intragastric tube or a single meal containing 2% cholesterol, it was demonstrated that rat liver hydroxymethylglutaryl-coenzyme A reductase [mevalonate: NADP+ oxidoreductase (CoA-acylating), EC 1.1.1.34 ] (HMG-CoA reductase) the major regulatory enzyme in cholesterol biosynthesis, is subject to two phases of inhibition. The first phase of inhibition is explained by in vivo phosphorylation of the enzyme; however, the nature of the second phase of inhibition remained obscure. The present study tested two possible explanations for this second phase of inhibition--increased enzyme turnover leading to a decreased concentration of HMG-CoA reductase molecules, and further inactivation of existing enzyme molecules. The results with the technique of immunotitration of HMG-CoA reductase show that, in short-term studies conducted up to 2 hr after the administration of a single dose of mevalonolactone or up to 6 hr after a single meal of rat chow containing 2% cholesterol, the in vivo regulation of rat liver HMG-CoA reductase during the first half of the dark period does not occur by increased enzyme turnover but, instead, existing enzyme is further inactivated.
