Inhibition by Zn2+ of A-form Monoamine Oxidase in Monkey Brain Mitochondria

Abstract

The effects of ZnSO4 on mitochondrial monoamine oxidase (MAO) activity in monkey brain were compared with those in rat and rabbit, in vitro. After preincubation at 25°C for 20 min with 1 μM ZnSO4, MAO-A activity in monkey brain was about 50% using serotonin (5-HT) as a substrate, and the inhibition was proportional to the concentration of ZnSO4. However, ZnSO4 had no effect on MAO-B activity in monkey brain using β-phenylethylamine (β-PEA) as a substrate. The inhibition by ZnSO4 of MAO-A activity was competitive and reversible. CdSO4 also inhibits MAO-A, but not MAO-B in monkey brain mitochondria. ZnSO4 did not inhibit either MAO-A or MAO-B activity in rat and rabbit brain mitochondria. These results indicate that the inhibiting action of Zn2+ differs depending on animal species. In monkey brain mitochondria, MAO-A was highly sensitive to Zn2+ and MAO-B was less sensitive. These results also suggest that Zn2+ may regulate the level of catecholamine content in monkey brain.