Catechol-O-methyltransferase (COMT) from pig liver is used in biochemical research to study the O-methylation of catechol-containing compounds, particularly catecholamines such as dopamine, norepinephrine, and epinephrine. It plays a key role in elucidating metabolic pathways for neurotransmitters and certain hormones, aiding in the understanding of neurotransmitter degradation and homeostasis. In drug development, it is employed to evaluate enzyme inhibitors and modulators, which are relevant for treating conditions like Parkinson's disease, schizophrenia, and pain management. This enzyme is also utilized in in vitro assays to measure methylation activity and in studies of phase II drug metabolism.