Multiple Forms of Arylalkylamine N‐Acetyltransferases in the Rat Pineal Gland: Purification of One Molecular Form

Rat pineal serotonin N‐acetyltransferase (EC 2.3.1.87) activity is isolated in two molecular forms (M_r≅ 10,000 95,000) by high performance size exclusion liquid chromatography in the presence of ammonium acetate (0.1 M, pH 6.5). In the presence of sodium citrate (0.1 M, pH 6.5), however, it is eluted as a single peak of intermediate size (M_r= 30,000). A highly enriched preparation of one of the molecular forms has been obtained by a two‐step purification procedure involving disulfide‐exchange anion‐exchange chromatography. The N‐acetyltransferase in 250 pineal glands obtained from isoproterenol‐treated rats can be purified about 80‐fold in 1 day; recovery is about 3%. Polyacrylamide gel electrophoresis of the final preparation indicates that a single major b(M_r≅ 11,000) is present; this appears to be serotonin N‐acetyltransferase.