IMPROVED ASSAY OF REACTION-PRODUCTS TO QUANTITATE CATECHOL-O-METHYLTRANSFERASE ACTIVITY BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH ELECTROCHEMICAL DETECTION

We applied coulometric detection (three electrochemical electrodes in series) to quantitate vanillic acid and isovanillic acid using reverse d-phase HPLC. The formation of these reaction products from dihydroxyb enzoic acid was used as a precise and reproducible measure of catechol -O-methyltransferase (COMT) activity in striatal homogenates and recom binant membrane-bound COMT protein. This detection system has a higher sensitivity (0.5 pmol per injection) than a single-cell amperometric detection. As in a previous method, the deproteinized supernatants of the COMT assay could be injected directly onto the HPLC system allowin g the handling of a large number of samples in one day.