Regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase

Within the last few years considerable evidence has accumulated which indicates that changes in HMG-CoA reductase are due primarily, if not solely, to changes in enzyme quantity. These include the changes caused by insulin, glucagon, cholesterol, mevalonolactone, cholestyramine, compactin, cyclic monoterpenes and the diurnal rhythm. Investigations of whether these changes in enzyme quantity primarily represent changes in rates of enzyme synthesis or degradation are just beginning. Regulation of reductase activity by reversible phosphorylation seems unlikely when all the available data are critically examined.