Melatonin: synthesis, significance, clinical relevance

2. Melatonin

Synthesis:

Step 1: Conversion to N-acetylserotonin:

• Enzyme: Arylalkylamine N-acetyltransferase (AANAT).

• Process: Serotonin is acetylated to form N-acetylserotonin.

• Mechanism: AANAT transfers an acetyl group from acetyl-CoA to serotonin, producing N-acetylserotonin.

Step 2: Conversion to Melatonin:

• Enzyme: Hydroxyindole-O-methyltransferase (HIOMT).

• Process: N-acetylserotonin is methylated to form melatonin.

• Mechanism: HIOMT transfers a methyl group from S-adenosylmethionine (SAMe) to N-acetylserotonin, producing melatonin.

Significance:

1. Sleep-Wake Cycle: Melatonin regulates the sleep-wake cycle by signaling to the body when it's time to sleep, aligning the internal clock with external light-dark cycles.

2. Antioxidant Properties: Melatonin has antioxidant effects, protecting cells from oxidative stress.

3. Immune Function: It supports the immune system and has anti-inflammatory properties.

Clinical Relevance:

• Sleep Disorders: Melatonin supplements are used to treat conditions like insomnia, jet lag, and circadian rhythm disorders.