Catalytic properties of liver monoamine oxidase in the chum salmon Oncorhynchus keta

The substrate and inhibitory specificity of mitochondrial monoamine oxidase (MAO) was studied in the summer-run male chum salmon Oncorhynchus keta liver. By the spectrum of deaminated substrates, chum salmon liver MAO is similar to that in most terrestrial mammals, with similarities in substrate characteristics found for eight classical MAO substrates. An assay of anti-monoamine oxidase efficacy of the two 2-propinilamine derivatives, five acridine derivatives and pyronine G revealed significant qualitative and quantitative differences as compared with tuna and whitefish liver MAO. The compounds tested were found to be irreversible inhibitors of chum salmon liver MAO exhibiting various efficacy, but lacking selectivity dependening on a deaminated substrate. The data of substrate–inhibitory analysis provide indirect evidence for the presence of a single molecular MAO form in the chum salmon liver.