Acetylserotonin O-methyltransferase

Acetylserotonin O-methyltransferase (ASMT) is an enzyme that in humans is encoded by the ASMT gene located on the X chromosome. This enzyme plays a crucial role in the biosynthesis of melatonin, a hormone primarily released by the pineal gland that regulates sleep and circadian rhythms. ASMT catalyzes the final step in melatonin synthesis, transferring a methyl group from S-adenosylmethionine (SAM) to N-acetylserotonin (NAS), thereby converting it into melatonin.

Function

The primary function of ASMT is the synthesis of melatonin from N-acetylserotonin. Melatonin has various biological roles, including the regulation of sleep-wake cycles, functioning as an antioxidant, and supporting immune function. The activity of ASMT, and thus melatonin synthesis, is influenced by the circadian clock, with higher activity during the night. This diurnal rhythm in ASMT activity contributes to the daily fluctuations in melatonin levels, which peak during the night.

Genetic Expression

The ASMT gene is expressed in the pineal gland and the retina, reflecting the role of melatonin in regulating circadian rhythms and potentially modulating visual functions. Variations in the ASMT gene have been studied in relation to sleep disorders, mood disorders, and other conditions influenced by melatonin levels.

Clinical Significance

Alterations in ASMT activity or expression can affect melatonin levels, potentially contributing to various health conditions. Low ASMT activity has been associated with sleep disorders, including insomnia and delayed sleep phase syndrome. Additionally, variations in the ASMT gene have been linked to mood disorders such as depression and bipolar disorder, suggesting a role for melatonin in mental health.

Research has also explored the relationship between ASMT and neurodevelopmental disorders, including autism spectrum disorder (ASD). Some studies suggest that mutations or variations in the ASMT gene may contribute to the etiology of ASD, possibly through effects on melatonin synthesis and circadian rhythm regulation.

See Also

• Melatonin
• Pineal gland
• Circadian rhythm
• S-adenosylmethionine
• N-acetylserotonin