Solubilization and partial purification of particulate catechol-O-methyltransferase from rat liver

Particulate catechol-O-methyltransferase (COMT) from rat liver has been solubilized by acetone treatment and partially purified. Results from the present study demonstrate that the solubilized, partially purified enzyme is similar to the cytosol COMT with respect to molecular weight, pH profile, sensitivity toward inhibitors, Mg2+ requirement, and substrate affinities. However, a comparison of the crude particulate COMT and the solubilized enzyme shows that there is a significant difference in their affinity for catechol substrates. This finding suggests that membrane protein and (or) lipid components may play an important role in catecholamine metabolism. The relationship of particulate COMT to [3H]norepinephrine binding was investigated. No correlation between the COMT and [3H]norepinephrine binding activities was observed in vitro.