Monoamine Oxidases: Versatility of Catalytic Properties and Possible Biological Functions

Abstract

This chapter discusses the phenomenon of monoamine oxidase transformation in mitochondrial membrane. A simple general method is developed based on well-recognized principles of protein chemistry, for solubilization of structure-bound monoamine oxidases. This method is successfully used for isolation and purification, under comparable conditions of structure-bound monoamine oxidases from mitochondrial membranes of rat liver, bovine liver, and bovine brain. The mitochondrial monoamine oxidases are prepared in nonsedimentable soluble form, without significant inactivation, by treating mitochondrial membranes with nonionic detergents in a strongly akaline medium with benzylamine—a substrate that exhibited high affinity toward active sites of monoamine oxidases and protected the enzymes from inactivation by alkalies. By means of subsequent ammonium sulfate fractionation and treatment with aluminum hydroxides, enzyme preparations were obtained, which as evidenced by electrophoresis in polyacrylamide gel and values of specific activity, are highly purified.