Abstract

Mitochondrial monoamine oxidase from a pig liver was rendered soluble by two‐fold extraction of mitochondrial phospholipids with methylethyl ketone according to Holluger and Oreland, and purified about 400 times.The influence of different compounds on the deamination of 2‐phenylethylamine its 4′‐chloro, 4′‐amino, 4′‐hydroxy derivatives and serotonin was studied.The interaction of monoamine oxidase with 1‐anilino‐8‐naphthalene sulphonate results in 15‐fold increase of the dye fluorescence accompanied by the shift of fluorescence maximum from 520 nm to 475 nm. It has been shown that 1‐anilino‐8‐naphthalene sulphonate inhibits deamination of tyramine, 2‐phenylethylamine and serotonin to the same degree.Alcohols, 1‐naphthol, 2‐naphthol and 8‐hydroxyquinoline inhibit deamination of tyramine and 2‐(4′‐aminophenyl) ethylamine in a much more pronounced fashion than that in the case of 2‐phenylethylamine and its 4′‐chloro derivative.Substitution of the benzene ring of 2‐phenylethylamine by pyridine or picoline causes the loss of the ability of corresponding amines to be affected by monoamine oxidase. 4‐Ethylpyridine and its iodomethylated and chlorobenzylated derivatives inhibit deamination of the unsubstituted 2‐phenylethylamine, its 4′‐chloro, 4′‐amino and 4′‐hydroxy derivatives and serotonin in different degree.Introduction of an electron‐accepting group into the 4‐ethylpyridine molecule significantly increased the inhibitory effect of the corresponding iodomethylate and chlorobenzylate on deamination of tyramine. At the same time the inhibition of oxidative deamination of serotonin is decreased.The data obtained confirm the conception that in the active centre of mitochondrial monoamine oxidase there are at least two substrate‐binding sites: a hydrophobic area and a definite polar site, which participate to a variable degree in binding of different amines.

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