SOME CHARACTERISTICS OF RAT LIVER MITOCHONDRIAL MONOAMINE OXIDASES

Abstract

This chapter presents a study examining characteristics of rat liver mitochondrial monoamine oxidases. The data discussed represents attempts at distinguishing the multiple monoamine oxidase (MAO) forms using polyacrylamide gel electrophoresis and some chromatographic separation procedures, detecting the MAO activity with benzylamine, serotonin and tyramine as substrates. For these experiments the mitochondria were treated with Lubrol W in presence of 0.1 M Tris–HCl buffer, pH 8.8, substrates and 30% sucrose w/v. The suspension was then sonicated for 15 min, centrifuged and the precipitate was discarded. In some experiments, the active supernatant was subjected to polyacrylamide gel electrophoresis. The acrylamide (spacer) gel was assayed without further division. Each thin disk constituted a fraction in which the MAO activity was detected using radioactive substrates. The gel electrophoresis of this crude preparation showed that benzylamine MAO activity migrated as a band to the anode and did not penetrate the acrylamideagarose gel, remaining in the acrylamide gel. The data obtained support the earlier findings that MAO can be separated into several fractions with different substrate specificities. The results indicate the occurrence of at least two enzymes with varying substrate specificities.