Monoamine Oxidaseに関する研究 : 第16報肝Mitochondria中のMAOの精製とその性格

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Two different types of monoamine oxidase (MAO) [EC 1. 4. 3. 4. monoamine: oxygen oxidoreductase (deaminating)], MAO-1 and MAO-2, were isolated and partially purified from beef liver by the procedure involving treatment of sodium cholate, 30_??_40% and 40_??_50% of ammonium sulfate fractionation, and chromatography of Sephadex G-50 and G-200. The specific activities of MAO-1 and MAO-2 were approx. 15-fold and 21-fold that of homogenate when tyramine was used as substrate. With n-butylamine as substrate, specific activities of both enzymes were different from that of tyramine. Enzymic properties of both enzymes were also studied, including pS maximum, optinal pH, substrate specificity, effects of various agents, such as p-methylphenylhydrazine (MPH), iproniazid (IIH), pheniprazine (JB-516), sodium nitrite and hydroxylamine. Results: 1) The pS maxima of various substrates for MAO-1 and MAO-2 were observed at the same concentration, but specific activities of MAO-2 at pS maxima of substrate examined were higher than those of MAO-1. 2) The pH optima of both enzymes with various substrates were observed at the same pH when tyramine and serotonin were used as substrates, but when β-phenylethylamine, benzylamine, n-amylamine and n-butylamine were used as substrates, different pHs were observed. 3) Substrate specificities of MAO-1 and MAO-2 were also studied. Both enzymes oxidized tyramine most rapidly. Moreover, MAO-2 oxidized n-butylamine, serotonin, n-amylamine, benzylamine and β-phenylethylamine in that decreasing order. MAO-1 slightly differed from that of the former enzyme in substrate specificity. 4) Both enzymic activities were inhibited by JB-516, MPH and IIH, however the degree of inhibition by addition of MPH or IIH differed between MAO-1 and MAO-2. In case of JB-516, the same degree of inhibition wasobserved for both enzymes. 5) Difference in effects of the other agents, such as sodium nitrite activated MAO-1 activity, but did not affect MAO-2 activity. Hydroxylamine generally inhibited both enzymes, but MAO-2 activity was inhibited more strongly than MAO-1 activity.

Monoamine Oxidaseに関する研究 : 第16報肝Mitochondria中のMAOの精製とその性格

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