THE NATURE OF THE ELECTROPHORETICALLY SEPARABLE FORMS OF MONOAMINE OXIDASE

Abstract

This chapter elaborates a study analyzing the nature of the electrophoretically separable forms of monoamine oxidase. Chaotropic agents have been shown to disrupt protein-lipid complexes by a weakening of hydrophobic bonds. In this study, the chaotropic agent, sodium perchlorate, was used to investigate the nature of Triton X-100 solubilized mitochondrial monoamine oxidase from rat liver and human brain. Polyacrylamide gel electrophoresis of the preparations gave rise to a number of bands of activity, although with the rat liver enzyme the band of activity which remained at the origin was found to be an artifact of the loading procedure. After treatment with sodium perchlorate, only a single band of monoamine oxidase activity could be detected. In the case of the rat liver enzyme, this band had a phospholipid content similar to that of the most mobile cathodically (least phospholipid containing) of the electrophoretically separable forms from the untreated enzyme. Gel filtration of the perchlorate-treated rat liver enzyme on Sepharose 4B indicated that no appreciable change in molecular weight had occurred, however an opalescent fraction could be separated which was shown to be rich in lipids, whilst little such material could be separated from the untreated enzyme.