Abstract
Monoamine oxidase (MAO) in hog kidney mitochondria was solubilized with a mixture of Triton X-100 and sodium cholate and the following results were obtained: Triton X-100 (1%) and sodium cholate (0.5%) almost completely solublized hog kidney mitochondrial MAO and no MAO activity was found in the precipitate after centrifugation at 100, 000×g for 1 hr. After the solubilization of hog kidney mitochondrial MAO by these detergents, about 30% increase in tryptamine oxidation was obtained, while all the oxidations of the other substrates, such as tyramine, 5-HT, PEA, benzylamine, octopamine and isoamylamine were decreased. A phenomenon almost similar to that in hog kidney was found for bovine kidney, too, but not in hog brain or rat liver. The increase in tryptamine oxidation was obtained with Triton X-100 alone or in combination with sodium cholate, but not with sodium cholate alone. The pargyline-induced inhibition of hog kidney MAO was increased after treatment with Triton X-100, both with tyramine and tryptamine as substrates, while inhibition by harmine was not changed. From these results, it was suggested that there might be an enzyme which is specific for the oxidation of tryptamine in hog kidney cortex, and it might play a special role in tryptophan metabolism in the kidneys of many species of animals.
