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 (Mr approximately equal to 10,000 and 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 (Mr approximately equal to 30,000). A highly enriched preparation of one of the molecular forms has been obtained by a two-step purification procedure involving disulfide-exchange and 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 band (Mr approximately equal to 11,000) is present; this appears to be serotonin N-acetyltransferase.