The inhibition by clorgyline of 5-hydroxytryptamine deamination by the rat liver.

The inhibition of the monoamine oxidase activity in the rat liver by the substrate selective inhibitor clorgyline has been investigated with 5-hydroxytryptamine as substrate. The results obtained are consistent with a theoretical model whereby the inhibition of enzyme activity by clorgyline follows a reversible association phase leading to an irreversible 'suicide' reaction. The relative concentrations of enzyme and inhibitor are of the same order, and can account both for the failure of the reaction to go to completion, and for the differences in the apparent sensitivity of enzyme preparations to inhibition by clorgyline. The possible value of this type of inhibition as a means of assay for monoamine oxidase active centres is discussed.