title: 3-Hydroxy-3-methylglutaryl-coenzyme A reductase is present in peroxisomes in normal rat liver cells.
abstract: The location inside rat liver parenchymal cells of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase; EC 1.1.1.34), the key regulatory enzyme in cholesterol biosynthesis, has been examined by immunoelectron microscopy and by subcellular fractionation. Although HMG-CoA reductase is generally thought to be exclusively a microsomal enzyme, we find that a substantial portion of cellular HMG-CoA reductase is localized in peroxisomes. Immunoelectron microscopic labeling of ultrathin frozen sections of normal rat liver, using two monoclonal antibodies to purified HMG-CoA reductase, showed that the enzyme is present in the peroxisomes at a higher concentration than at any other site inside the hepatocytes. Subcellular fractionation studies using Percoll and metrizamide gradients demonstrated a close correspondence of peaks of HMG-CoA reductase activity and of catalase activity, again revealing the presence of the reductase enzyme in peroxisomes. HMG-CoA reductase is therefore localized in peroxisomes in addition to being in the microsomal fraction.
mesh_terms: D000818:Animals; D002499:Centrifugation, Density Gradient; D005260:Female; D006903:Hydroxymethylglutaryl CoA Reductases / Q000032:analysis*; D007158:Immunologic Techniques; D008099:Liver / Q000648:ultrastructure*; D051379:Mice; D008830:Microbodies / Q000201:enzymology*; D008854:Microscopy, Electron; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D006903:Hydroxymethylglutaryl CoA Reductases