Factors which interfere in the manometric assay of monoamine oxidase

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Abstract
The occurrence in washed rat-liver mitochondria of enzymes likely to modify the O2 uptake during the oxidative deamination of isopentylamine or tyramine was studied. Catalase and peroxidase were present and active. Peroxidase was inhibited by 0.01 [image] azide and by 10-3 [image] cyanide. Catalase was not inhibited by 2 x 10-6 [image] 2:4-dichlorophenol or by 0.01 [image] semicarbazide; it was incompletely inhibited by 0.05 [image] cyanide. Cytochrome oxidase was present but inactive owing to the absence of sufficient cytochrome c. The enzyme was inhibited by 10-3 [image] cyanide. Aldehyde oxidase was not detected. The effects of cyanide, semicarbazide, azide and ethanol on O2 uptake during the deamination of tyramine and isopentylamine were studied, and the results discussed. It is concluded that a buffered reaction mixture containing the monoamine oxidase preparation, 0.01 [image] [tyramine, 0.01 [image] semicarbazide and 10-3 [image] cyanide is suitable for measuring monoamine oxidase activity. Under these conditions one atom of oxygen is absorbed for each molecule of substrate oxidized and the O2 absorbed at 30 minutes is proportional to the monoamine oxidase concentration.

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