N acetyltransferase of brain: some properties of the enzyme and the identification of β carboline inhibitor compounds

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.