acetylserotonin

Acetylserotonin, or N-acetyl-5-hydroxytryptamine, is an amide derivative of the neurotransmitter serotonin. It is best known as an intermediate in the biosynthesis of melatonin, the circadian hormone.

In mammals, serotonin is acetylated by the enzyme arylalkylamine N-acetyltransferase (AANAT) to form N-acetylserotonin. This compound is then methylated by hydroxyindole O-methyltransferase (HIOMT, also known as ASMT) to produce melatonin. Thus, acetylserotonin occupies a central position in the enzymatic pathway linking serotonin to melatonin.

Acetylserotonin is found in tissues where serotonin is produced, most notably in the pineal gland and retina, and it can be detected in small amounts in blood and other organs. Its levels and turnover are influenced by the circadian clock, reflecting its role as a precursor to melatonin, whose synthesis peaks at night.

The primary physiological significance of acetylserotonin is as a precursor to melatonin. While its exact independent signaling roles are less well defined, acetylserotonin is generally regarded as a transient intermediate in the seasonal and daily regulation of melatonin production rather than a widely acting messenger in its own right.

Chemically, acetylserotonin is the N-acetyl derivative of serotonin, sharing the indoleamine core. It is one step in the well-characterized melatonin biosynthetic pathway, linking serotonin to the end product melatonin.