Catechol O-methyltransferase, porcine liver (COMT), the magnesium-dependent transfer of methyl groups from S-adenosyl methionine to a hydroxyl group on dopamine, converting it to 3-methoxytyramine. Catechol O-methyltransferase has two forms in tissues, a soluble form (S-COMT) and a membrane-bound form (MB-COMT). Catechol O-methyltransferase is to regulate epinephrine, norepinephrine, and dopamine levels in the brain.
References:
[1]. Du X, et, al. A catechol-O-methyltransferase that is essential for auditory function in mice and humans. Proc Natl Acad Sci U S A. 2008 Sep 23;105(38):14609-14.