Abstract

Several β-carboline derivatives, such as harmane, harmol, 6-methoxyharman, and melatonin, inhibited the N-acetylation of tryptamine by brain N-acetyltransferase. The enzyme of brain was active toward several indole- and phenylethylamine substrates. In contrast to the enzyme of brain, the enzyme of pineal was not inhibited by harmaline and harman, and 3,4-dimethoxyphenylethylamine was a relatively poor substrate. β-carboline inhibitors may be useful aids for studying the various N-acetyltransferases and for evaluating the physiological role of the brain enzyme.