Inhibition of monoamine oxidase action on kynuramine by substrate amines and stereoisomeric α-methyl amines

Kynuramine oxidation by rat liver monoamine oxidase was inhibited by dopamine, norepinephrine, phenethylamine, phenylbutylamine, serotonin, or tyramine. Although these were all substrates for the enzyme preparation, there was no consistent relationship between degree of inhibition and efficacy as substrate. The α-methyl analogues of dopamine, norepinephrine, phenethylamine, tyramine, or 4-chlorophenethylamine also inhibited kynuramine oxidation. The degree of inhibition by the α-methyl compounds was, in most cases, less than that by the parent compounds. Inhibition of MAO by α-methyl amines (amphetamine, 2, 4-dichloroamphetamine, 4-chloro-N-methyl-amphetamine, or 3, 4-dichloroamphetamine) was greater with the dextrorotatory isomers than with the levorotatory isomers.