Liver Monoamine Oxidase Activity of the Lamprey Lampetra fluviatilis. The Substrate-Inhibitor Specificity

Based on the data of substrate-inhibitor analysis with the use of specific inhibitors-deprenyl, chlorgilin, and specific substrates-serotonin, noradrenalin, benzylamine, beta-phenylethylamine and N-methylhistamine, one molecular form of monoamine oxidase (MAO) was suggested to possibly exist in liver of mature individuals of the European lamprey Lampetra fluviatilis. The kinetic parameters of monoamine oxidase deamination of eight substrates were determined, which indicates the large spectrum of substrate specificity of MAO from the lamprey liver. The studied enzyme does not deaminate histamine and putrescine and is not sensitive to 10(-2) M semicarbaside. Results of the study of the substrate-inhibitor specificity allow us to suggest some resemblance in catalytic properties of the lamprey liver MAO and the mammalian MAO of the form A. The low activity of the enzyme revealed at deamination of all used substrates seems to be associated with low detoxifying function of the lamprey liver.