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：1983
卷号：80
期号：8
页码：2171-2174
DOI：10.1073/pnas.80.8.2171
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Acyl-coenzyme A:cholesterol O-acyltransferase (ACATase; EC 2.3.1.26 ) is a membrane-bound microsomal enzyme that catalyzes the formation of long-chain fatty-acyl cholesterol esters in rat liver and other tissues. This enzyme is important in regulating the concentration of unesterified cholesterol in the cell. Having recently demonstrated that rat liver 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase; EC 1.1.1.34 ), the major regulatory enzyme in cholesterol biosynthesis, undergoes in vivo phosphorylation and inactivation after a single cholesterol meal, we decided to test the hypothesis that the enzyme ACATase, important in cholesterol utilization and storage, is also subject to regulation by phosphorylation/dephosphorylation. The results show that rat liver ACATase can be reversibly inactivated/activated, in vitro, by incubation conditions that favor dephosphorylation/phosphorylation. Activation was also achieved by using a partially purified protein kinase extracted from microsomes. It is significant that HMG-CoA reductase is inactivated by phosphorylation whereas ACATase is activated by phosphorylation. ACATase is, therefore, regulated by phosphorylation in a manner exactly opposite to that of HMG-CoA reductase. We propose that the coordinate regulation of ACATase and HMG-CoA reductase by phosphorylation/dephosphorylation provides a mechanism for short-term intracellular cholesterol homeostasis.
