Acetylserotonin methyltransferase (hydroxyindole-O-methyltransferase; EC 2.1.1.4 ) catalyzes the final reaction in the synthesis of melatonin and is abundant in the pineal gland and retina. Donohue et al. (1993) isolated a clone with sequence homology to bovine HIOMT from a human pineal cDNA library.
General function
Metabolism, Enzyme, Transferase
Comment
Cellular localization
Cytoplasmic
Comment
Ovarian function
Steroid metabolism
Comment
Melatonin, the enzymatic product of HIOMT, has been shown to regulate ovarian cell steroidogenesis (see Melatonin receptor gene file).
Expression regulated by
Comment
Ovarian localization
Oocyte
Comment
PMID: 22951050
The presence of melatonin (N-acetyl-5-methoxytryptamine) and its precursors, serotonin
(5-hydroxytryptamine) and N-acetylserotonin, was demonstrated in extracts of human and rat ovaries by Itoh et al using reverse-phase high-performance liquid chromatography coupled with fluorometric detection. In addition, activities of two melatonin-synthesizing enzymes, arylalkylamine N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT), were found in human ovary homogenates (Itoh et al. 1997; and 1999). Brzezinski et al. (1987) investigated if melatonin is present in the human ovary. Preovulatory follicular fluids from infertile women undergoing in vitro fertilization and embryo transfer were assayed for melatonin by RIA after solvent extraction. All of the follicular fluids contained melatonin, in concentrations substantially higher than those in the corresponding serum.