PER2

This gene is a member of the Period family of genes and is expressed as the primary circadian pacemaker in the mammalian brain.

Genes in this family encode components of the circadian rhythms of locomotor activity, metabolism, and behavior.  Polymorphisms in this gene may have been linked to sleep disorders.

Melatonin has an agonistic action on the PER2 enzyme and can help to improve sleep.