Enables catechol O-methyltransferase activity. Acts upstream of or within cellular response to phosphate starvation and dopamine catabolic process. Located in mitochondrion. Is expressed in several structures, including alimentary system; cardiovascular system; central nervous system; genitourinary system; and sensory organ. Used to study cognitive disorder and pre-eclampsia. 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]