Beta-phenylethylamine: a specific substrate for type B monoamine oxidase of brain.

Abstract

β-Phenylethylamine and serotonin were oxidatively deaminated by separate forms of monoamine oxidase of rat brain wimen studied in vitro . These forms, designated as type A and type B enzyme, have different characteristics. For example, type A enzyme deaminated serotonin, was sensitive to the drug clorgyline, was resistant to the drug deprenyl and was heat-stable. In contrast, type B enzyme deaminated β-phenylethylamine, was resistant to clorgyline, was sensitive to deprenyl and was heat-labile. Moreover, type A and type B enzyme activities could be partially separated by centrifugation on a continuous sucrose gradient. β-Phenylethylamine and serotonin are present in mammalian brain. We conclude from our studies that the amines of brain may be cataboblized by specific types of monoamine oxidase in vivo .