[The reactivity of liver monoamine oxidase in the ringed seal Phoca hispida ladogensis]

The goal of the work consisted in study of substrate and inhibitor specificity of liver monoamine oxidase (MAO) of the freshwater Ladoga subspecies of the ringed seal Phoca hispida ladogensis. The studied enzyme has been established to have large substrate specificity by deaminating, apart from eight classic substrates of MAO of terrestrial mammals, also histamine, the diamine oxidase substrate. It is found out that the deamination rates of benzylamine, beta-phenylethylamine, and N-methylhistamine almost one order higher than rates of deamination of serotonin and noradrenaline. MAO of the seal liver does not deamnate putrescine and cadaverine and is not sensitive to 10(-2) M semicarbazide. We calculated bimolecular constants of interaction rates of inhibitors chlorgiline, deprenyl, berberine, sanguinarine, chelidonine, and four derivatives of acridine with the enzyme at deamination of nine substrates. By the method of the substrate-inhibitor analysis, we showed the enzyme heterogeneity, i. e., the existence in the seal liver of at least two different MAO.