Human Plasma Monoamine Oxidase

Amine oxidases that occur in the plasma of mammals have been intensively studied in recent years (l-8). The ability of human plasma and serum to convert benzylamine to benzaldehyde has recently been demonstrated (9). Evidence has been presented to show that this enzymatic activity is different from other human plasma enzymes that catalyze the oxidation of amines (i.e. ceruloplasmin and diamine oxidase) (9, 10). The present paper reports the purification of this monoamine oxidase activity from human plasma. It also defines the substrate specificity of the purified enzyme, the stoichiometry of the reaction it catalyzes, and inhibitors of the reaction.1