Major degradative enzyme for catecholamine neurotransmitters; methylates the o-hydroxyl group

One unit will produce 1.0 nanomole of total O-methylated products from 3,4 dihydroxyacetophenone per hour at pH 7.6 at 37 °C.
Previous radioactive assay unit definition: One unit will catalyze the methylation of 1.0 nanomole of protocatechuic acid per hr at pH 7.9 at 37°C using S-adenosyl-L-[methyl-¹⁴C]methionine as the methyl donor. (~6 radioactive units equal one new unit).

Lyophilized powder containing phosphate buffer and dithiothreitol