Effects of zinc ion on type A monoamine oxidase in monkey brain mitochondria.

Abstract The effects of ZnSO 4 on types A and B monoamine oxidase (MAO) isozymes in monkey brain mitochondria were investigated, in vitr o. Type A MAO activity in monkey brain decreased to about 50% with 1 μM ZnSO 4 using serotonin as a substrate, and this inhibition was proportional to the concentration of ZnSO 4 . ZnSO 4 had no effect, however, on type B MAO activity in monkey brain using β-phenylethylamine as a substrate. The inhibition by ZnSO 4 of type A MAO activity was competitive and reversible. ZnSO 4 did not inhibit either type A or type B MAO activity in rat brain mitochondria. Almost similar results were also obtained when ZnCl 2 was used, in vitr o. These results indicate that the inhibiting action of zinc ion differs depending on animal species and organ. Type A MAO in monkey brain mitochondria was highly sensitive to zinc ion, while type B activity was less sensitive.