Anion inhibition of monoamine oxidase

It was found that rat liver monoamine oxidase is inhibited by various anions and that the degree of inhibition depends on which of two substrates, serotonin or tyramine, is used to test the monoamine oxidase activity. In addition, the inhibition by anions is affected by pH and temperature in ways that differ with the two substrates: for example, with rising temperatures inhibition of tyramine deamination by salts increases while inhibition of serotonin deamination decreases. The differential inhibition of MAO by anions suggests the existence of more than one active site or more than one enzyme subunit in rat liver monoamine oxidase. The relative substrate specificity of the inhibitions by anions suggests that there might exist other substrate-specific inhibitors.