[Catalytic characteristics of monoamine oxidase of whitefish Coregonus lavaretus ludoga].

Study of substrate-inhibitory specificity of liver mitochondrial monoamine oxidase (MAO) of sexually mature individuals of the whitefish Coregonus lavaretus ludoga P. from the Ladoga Lake has revealed distinguished peculiarities of catalytical properties of this enzyme. The studied MAO, on one hand, like the classical enzyme of homoiothermal animals, is able to deaminate tyramine, serotonin, benzylamine, tryptamine, and beta-phenylalanine, but, on the other hand, to deaminate histamine, the classic substrate of diamine oxidase. The found equal activity and sorptional ability of the enzyme toward six studied substrates including histamine, as well as results of the substrate-inhibitory analysis with use of specific inhibitors--deprenyl and chlorgilin--indicate homogeneity of the enzyme. The detected for the first time among the fish MAO wide substrate specificity and an unusually low sensitivity to both studied acetylene inhibitors does not allow ascribing unanimously the studied enzyme to the known MAO forms of organs and tissues of homoiothermal organisms. Apparently, the revealed enzyme form of poikilothermal organism is not the true MAO, but performs a large amine oxidase function.