Monoamine oxidaseに関する研究-19-Monoamine oxidase反応系中における生成物のmonoamine oxidaseに対する影響
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MAO (monoamine oxidase) has been found in many organs in animals and known as an enzyme which deaminate monoamines oxidatively such as adrenaline and serotonin. MAO catalyzes stoichiometrically the oxidation of monoamines with consumption of one mole of O<SUB>2</SUB> and produced one mole of aldehyde, NH<SUB>3</SUB> and H<SUB>2</SUB>O<SUB>2</SUB>. However, in case of the presence of catalase in enzyme preparation, H<SUB>2</SUB>O<SUB>2</SUB> is converted to one mole of H2O and half mole of O<SUB>2</SUB>. In case of MAO activity is assayed by oxygen consumption, catalase may play some influence on the reaction system of MAO.<BR>Effect of KCN and NaN<SUB>3</SUB> which are known as the inhibitors of catalase on oxygen consumption in the reaction system of MAO are studied using mitochondrial MAO and soluble MAO from beef liver as enzyme preparations.<BR>Following results were obtained :<BR>1. When mitochondrial MAO was used as an enzyme preparation, the amount of oxygen consumption in the reaction system of MAO was more than the stoichiometrio consumption.<BR>2. In case of soluble MAO was used as an enzyme preparation, MAO catalyzed the oxidation with the consumption of half mole of O<SUB>2</SUB> which is same as the case of the presence of catalase in the reaction system of MAO.<BR>3. KCN and NaN<SUB>3</SUB> showed marked inhibition of catalase activity at the concentration from 1 × 10<SUP>-1</SUP> M to 1 × 10<SUP>-4</SUP> M in case of the initial reaction was measured by an oxygen electrode. Consequently, NaN<SUB>3</SUB> activated MAO activity and showed increase of oxygen consumption in the reaction system of MAO. These effects were not observed in case of manometric assay. In case of MAO assay with an oxygen electrode, MAO activity was increased at the concentration of 1 × 10<SUP>-2</SUP> M KCN, but was decreased at the other concentrations of KCN. However, the oxygen consumption in the reaction system of MAO was decreased at all concentration of KCN tested in case of manometric assay.<BR>4. When tyramine was used as substrate, the oxygen consumption in the reaction system of MAO was increased with the addition of NH<SUB>3</SUB> in manometric assay.<BR>From the experimental results obtained in this paper, it is considered that the increase of oxygen consumption than stochiometric amount in case of mitochondrial preparation was used, was mainly due to the presence of the other oxidative enzymes such as cytochrome oxidase and peroxidase etc.<BR>The products in the reaction system of MAO such as aldehyde, NH<SUB>3</SUB> and H<SUB>2</SUB>O<SUB>2</SUB> showed marked influences to the oxygen consumption in reaction system of MAO.
- 学校法人 昭和大学・昭和医学会の論文
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