The effect of harmine and other monoamine oxidase inhibitors on N-acetyltransferase activity

Prior studies indicate that the monoamine oxidase inhibitors (MAOI) harmine and iproniazide inhibit N-acetyltransferase activity from liver. In this report we have demonstrated that harmine and harmaline are potent inhibitors of N-acetyltransferase, purified from hamster and rat liver. However, other MAOI such as deprenyl, clorgyline, methysergide, cyproheptadine, phenelzine, pargyline, methyltryptamine and tranylcypromine have either no effect, or only trivial effects on N-acetyltransferase. There is no correlation between a compound's properties as an MAO and N-acetyltransferase inhibitor. One must consider the inhibitory effect of harmine and harmaline on both MAO and N-acetyltransferase when evaluating the effects of these compounds on physiological processes.