Enables catechol O-methyltransferase activity. Involved in several processes, including learning or memory; negative regulation of smooth muscle cell proliferation; and regulation of cellular amine metabolic process. Located in several cellular components, including cell body; dendritic spine; and postsynaptic membrane. Used to study Parkinsonism and hypertension. Biomarker of hypertension. Human ortholog(s) of this gene implicated in several diseases, including attention deficit hyperactivity disorder; autoimmune disease of skin and connective tissue (multiple); bulimia nervosa; cognitive disorder (multiple); and reproductive organ cancer (multiple). Orthologous to human COMT (catechol-O-methyltransferase). [provided by Alliance of Genome Resources, Apr 2022]