[Comparative enzymological study of catalytic properties of sturgeon fish liver monoamine oxidases]

We performed comparative study of substrate and inhibitor specificity of liver monoamine oxidases (MAO) of the giant sturgeon Huso huso, starred sturgeon Asipenser stellatus, Persian sturgeon Asipenser persicus, and Russian sturgeon Asipenser gueldenstaedtii. Results of the substrate-inhibitor analysis with use of inhibitors chlorgilin and deprenil, as well as of five specific substrates indicate homogeneity of these enzymes. All studied MAO have several orders higher sensitivity to chlorgilin than that to deprenil, the essential interspecies differences being observed. There are determined kinetical parameters of enzymatic deamination (K(M) and V) of tyramine, serotonin, noradrenalin, benzylamine, beta-phenylethylamine, and N-methylhistamine. It is found that all studied enzymes show the higher activity toward serotonin and noradrenalin--substrates of the MAO form A, as compared with benzylamine, beta-phenylethylamine, and N-methylhistamine--substrates of the MAO form B of mammals, the maximal activity being shown by enzyme of the giant sturgeon.