THE CELLULAR-LOCALIZATION OF MALONYL-COENZYME-A DECARBOXYLASE IN RAT-BRAIN

Malonyl-coenzyme A (CoA) decarboxylase (E.C.4.1.1.9) activity in brain is low but steadily increases after birth. The main physiological rol e of this mitochondrial enzyme is thought to be the stabilization of m alonyl-CoA levels which change very little with brain growth. In an ef fort to visualize malonyl-CoA decarboxylase by immunocytochemistry, an d to determine its developmental changes, the enzyme was purified by a n efficient small-scale procedure involving isolation of mitochondria, extraction at high ionic strength, isoelectric focusing, column chrom atography, and preparative polyacrylamide gel electrophoresis. The enz yme from brain showed the same apparent molecular weight (160 kDa) and was immunoreactive with antisera raised against malonyl-CoA decarboxy lase from liver. Immunocytochemistry revealed early and extensive labe ling of hepatocytes in rat liver but only delayed visualization in the brain. Most nerve cells of the cerebral cortex and many microglia wer e stained but the neurons of the cerebellar cortex did not become reac tive. Golgi epithelial cells and their processes, the Bergmann glia, a lso showed reaction product.