Arylamine N-acetyltransferase and arylalkylamine N-acetyltransferase in the mammalian pineal gland

J Biol Chem. 1984 Sep 10;259(17):10913-8.


Amine N-acetylation in the pineal gland is of special importance because it is the first step in the synthesis of melatonin from serotonin. In the present study the N-acetylation of arylamines and arylalkylamines by homogenates of rat and sheep pineal glands was investigated. The arylamines studied were p-phenetidine and aniline; the arylalkylamines studied were tryptamine, serotonin, 5-methoxytryptamine, 6-fluorotryptamine, and phenylethylamine. These amines were acetylated by pineal homogenates of both species, although marked interspecies differences in apparent Km and Vmax values were found. A series of observations in both species indicate that aromatic amine N-acetylation is catalyzed by two distinct enzymes; one preferentially acetylates arylamines and the other preferentially acetylates arylalkylamines. First, isoproterenol treatment of the rat increased arylalkylamine N-acetylation 100-fold without increasing arylamine N-acetylation. Second, cycloheximide treatment in sheep reduced arylalkylamine N-acetylation at night to one-tenth control values, without altering arylamine N-acetylation. Third, arylamine N-acetyltransferase and arylalkylamine N-acetyltransferase inactivated at different rates at 4 degrees C. Fourth, the two enzymes were resolved by size exclusion chromatography. These results clearly establish that the pineal gland contains an arylamine N-acetyltransferase and a second, independently regulated arylalkylamine N-acetyltransferase which appears to be primarily responsible for the physiological conversion of serotonin to melatonin via the intermediate N-acetylserotonin.

Publication types

  • Comparative Study

MeSH terms

  • Acetylation
  • Acetyltransferases / metabolism*
  • Animals
  • Arylamine N-Acetyltransferase / isolation & purification
  • Arylamine N-Acetyltransferase / metabolism*
  • Cycloheximide / pharmacology
  • Isoproterenol / pharmacology
  • Kinetics
  • Pineal Gland / drug effects
  • Pineal Gland / enzymology*
  • Rats
  • Rats, Inbred Strains
  • Sheep
  • Substrate Specificity


  • Cycloheximide
  • Acetyltransferases
  • Arylamine N-Acetyltransferase
  • Isoproterenol