DIFFERENTIAL METABOLISM OF VARIOUS BRAIN REGIONS. BIOCHEMICAL HETEROGENEITY OF MITOCHONDRIA

Abstract

Cytochrome-oxidase activity was determined in mitochondrial fractions from cerebral cortex, cerebellum, thalamus and corpus callosum of monkey brain. The enzyme activity in corpus callosum/mg of mitochondrial protein is significantly lower than the specific activity of the enzyme in cerebellum or cerebral cortex, the values in thalamus being intermediate. This is also true when the mitochondrial fraction has been further purified by density-gradient fractionation. The apparent Km values of the enzyme for cytochrome c also differ. The enzymes in these areas have similar pH optima and are inhibited in a parallel manner with phosphate ions. The mitochondrial fraction from the neuroglial tissue of the corpus callosum appears to be constitutionally different from that of cerebellum or cerebral cortex.