Gonadal steroid regulation of pineal melatonin synthesis.

The regulation of gonadal function by the vertebrate pineal, primarily through the biological actions of melatonin has received much attention from investigators during the past decade (1–5). Melatonin is synthesized from serotonin through the activities of the pineal enzymes N-acetyl transferase (NAT) and hydroxyindole-O-methyl transferase (HIOMT). NAT converts serotonin to N-acetyl serotonin by coupling of the acetyl function from Acetyl Coenzyme A to serotonin. HIOMT transfers the methyl group from S-adenosylmethionine to N-acetyl serotonin, to form melatonin.