STUDIES ON MONOAMINE OXIDASE (REPORT 13) ISOLATION OF TWO DIFFERENT TYPES OF MONOAMINE OXIDASE FROM BEEF LIVER MITOCHONDRIA

[摘要] References(42)Cited-By(12)Studies on the subcellular distribution of monoamine oxidase (MAO) [EC 1.4.3.4. monoamine: oxygen oxidoreductase (deaminating)] have shown that the enzymic activity is mainly associated with the mitochondrial fraction (1-5). However, recently appreciable activities have been found in the other particulate fractions (6-8), and in the soluble fraction (9). There have been numerous reports on the role of MAO in metabolism and its possible importance in control of amine levels in the brain. From results on the substrate specificities and effect of temperature on mitochondrial MAO, Oswald and Strittmatter (8) postulated that various tissues may contain several kinds of MAO, or different groups of enzymes. Gorkin et al. (10-12) confirmed indirectly the “multiplicity” of mitochondrial and partially purified MAO in experiments on differences in inhibitor sensitivities and types of inhibition. Fujimaki (13) separated two distinct spots of MAO activity from preparation of rat liver and brain by electrophoresis. Watanabe et al. (14) also reported that during starvation the pattern of changing in MAO activity in rat liver differed from that in brain. MAO has only been partially purified because it is difficult to solubilize it from mitochondria, but recently mitochondrial MAO has been purified to various extents in several laboratories (15-20). Preliminary observations in our laboratory showed that partially purified mitochondrial MAO from beef liver, which had been solubilized with sodium cholate could be separated into two fractions by precipitation with ammonium sulfate. These were named MAO-1 and MAO-2, respectively (21). The present work was the different enzymic properties of the two enzymes, including their substrate specificities, pH optima and Michaelis constants and the effects of various metal ions, chelating agents, and heat treatment on them.

[学科分类] 药理学