A Novel Type Mitochondrial Monoamine Oxidase from the Liver of Skipjack Tuna (Katsuwonus pelamis): Purification and Characterisation

A novel type of monoamine oxidase (EC. 1.4.3.4) present in the liver of skipjack tuna (Katsuwonus pelamis) was extracted from mitochondrial preparations by Triton X-100. The enzyme was purified by ammonium sulphate fractionation, followed by Sephadex G-200, butyl-toyopearl 650 M, phenyl-toyopearl 650 M and hydroxyapatite chromatography. The molecular weight of the enzyme was estimated to be about 110000 by gel filtration on Sephadex G-200. The enzyme was activated by Mn²⁺, but was inhibited by Cu²⁺, Zn²⁺ and p-chloromercuribenzoic acid (PCMB). Furthermore, the enzyme was completely inhibited by Hg²⁺ and 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB). © 1997 SCI.