Inhibition of monoamine oxidase by the fungicide metalaxyl.

The in vitro effect of metalaxyl on monoamine oxidase (MAO) activity in rat heart was studied. Metalaxyl decreased MAO activity in a dose-dependent manner. The inhibitory concentration (IC50) for metalaxyl was found to be 19 mumol. Substrate-dependent kinetic studies demonstrated noncompetitive inhibition as evidenced by decreased velocity of enzyme activity (Vmax) without significant change in enzyme-substrate affinity (Km). The inhibition of MAO activity by metalaxyl suggests interference with amine metabolism.