[6][7] N-Acetylserotonin O-methyltransferase is an enzyme that is coded for by genes located on the pseudoautosomal region of the X and Y chromosome, and is most abundantly found in the pineal gland and retina of humans.
This finding, in conjunction with research on alternative splicing of the HOIMT hnRNA, suggests that Hydroxyindole O-methyltransferase (synonym for N- Acetylserotonin O-methyltransferase) plays a role in the human immune system, in addition to its endocrine and nervous system functions.
The second reaction (Figure 4) catalyzed by N-Acetylserotonin O-methyltransferase in the tryptophan metabolism pathway is: S-Adenosyl-L-methionine + 5-Hydroxyindoleacetate ↔ S-Adenosyl-L-homocysteine + 5-Methoxyindoleacetate.
Abnormally high levels of HIOMT in these glands could serve as an indication of the existence of PPTs in the brain.
Melatonin levels can also be used as a state marker, contributing to conclusions on the severity of a patient's illness at a given point in time.
Because studies have shown a direct correlation between the amount of hydroxyindole-O-methyltransferase in the pineal gland and the melatonin level, additional knowledge of HIOMT could provide valuable insight on the nature and onset of these impairing disorders.
[15] Subjects with autism were found to have significantly lower levels of melatonin and acetylserotonin O-methyltransferase (ASMT) than controls.
[16] High frequency polymorphism exists on the PAR region of the sex chromosomes, where the HIOMT gene is located.
Linkage analysis of a diseased locus with high frequency polymorphism of this region could lead to vital information about the role of this gene in genetic disorders.
In 2001, it was argued that another enzyme in the pathway, N-acetyl transferase (NAT) was the limiting reagent in the production of melatonin.