MONOAMINE OXIDASE (EC 1.4.3.4): ISOLATION AND CHARACTERIZATION OF MULTIPLE FORMS OF THE BRAIN ENZYME

Abstract

Abstract Monoamine oxidase (MAO) in crude mitochondrial preparations from rat brain was solubilized, and different MAO‐active fractions were separated by agarose columns and by Sephadex electrophoresis. Any combination of these techniques yielded at least three fractions possessing MAO activity as measured by assays using radioactive serotonin and benzylamine as substrates. The molecular weight of one of the MAO forms was found to be approximately 400,000 daltons while another was at least 1.5 × 10 6 daltons. The crude mitochondria1 MAO was inhibited by [ 14 C]‐labelled pargyline and then solubilized and the radioactivity of the soluble and particulate MAO was compared to the enzyme activity found in the soluble and particulate fractions. Our studies suggest that appreciable MAO activity is lost upon solubilization and that the conformation of MAO may be altered.