PURIFICATION AND PROPERTIES OF MITOCHONDRIAL MONOAMINE-OXIDASE TYPE-AFROM SKIPJACK LIVER

Monoamine oxidase A (EC 1.4.3.4) in skipjack liver was extracted from mitochondrial preparations by Triton X-100. The enzyme was purified by ammonium sulfate fractionation, followed by chromatographies of Sepha dex G-200, Butyl Toyopearl 650 M, and hydroxyapatite. By this method a final specific activity of 19.5 units/mg and 30-fold purification wer e attained. The molecular weight of the final preparation was estimate d to be about 130,000 by gel filtration on Sephadex G-200. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated a subunit molecular mass of 64,000. The optimum pH was 9.0 and the enzy me was stable between pH 9.0 and 10.0 after incubation at 4 degrees C for 60 min. The optimum temperature was 30 degrees C. The enzyme was i nhibited by Ca2+, Mg2+ and Mn2+, but was activated by Cu2+. The enzyme showed a high activity by 5-hydroxytryptamine, tyramine and epinephri ne as substrates, but showed low activity by benzylamine and 2-phenyle thylamine.