Improved methods for the study of hepatic HMG CoA reductase: one-step isolation of mevalonolactone and rapid preparation of endoplasmic reticulum.

Two new methods are described for the study of hepatic 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase. (1) Endoplasmic reticulum was rapidly prepared by diluting a 10,000 g supernatant with buffer containing 8 mM calcium chloride. The yield of protein and the specific activity of HMG CoA reductase in the pellet subsequently obtained by low speed centrifugation were nearly identical to those in the microsomal pellet prepared by ultracentrifugation. This technique may be particularly useful in studies of the rapid, in vitro modulation of the enzyme. (2) Mevalonolactone was extracted into benzene from the HMG CoA reductase assay mixture with an efficiency of 58%. There was less than 1% extraction of HMG CoA, acetoacetate, or beta-hydroxybutyrate. The extracted mevalonolactone was at least 98% pure as judged by thin-layer chromatography with four different solvent systems. These improved methods should significantly aid studies of the physiological importance of HMG CoA reductase.