Inhibition of bovine plasma amine oxidase by superoxide dismutase active Cu(II) complexes

Aqueous Cu²⁺ and Cu(II) complexes of salicylate, lysine, and tyrosine decrease the rate of benzylamine oxidation by bovine plasma amine oxidase. Bissalicylato Cu(II) and Cu²⁺ inhibit non-competitively with respect to benzylamine. Lysine, tyrosine, Cu(EDTA)^2?, Zn²⁺, and Co²⁺ do not inhibit, and erythrocyte Cu, Zn superoxide dismutase shows only slight inhibition of the amine oxidase. The data are most consistent with an inhibitory mechanism involving dismutation of O₂^? by the Cu(II) complexes within a site relatively inaccessible to the enzyme superoxide dismutase. Excess lysine significantly decreases inhibition by the bis-lysine complex of Cu(II).