An enzyme catalyzing the discoloration and breakdown of betacyanins was isolated from beet roots Beta vulgaris by centrifugation in sucrose density gradient (2.5 M, 2.0 M, 1.5 M, 1.0 M, tris-HCl buffer, 0.05 M, pH 7.2), and purified 100-fold. The enzyme activity induced the discoloration of betanin, betanidin. It was found that the beet root enzyme exists in an insoluble state and is firmly bound with subcellular structures, which were isolated by centrifugation in sucrose gradient. The optimal activity of the enzyme was observed at pH 3.4, +40 degrees C. The dependence of the enzymatic reaction on the enzyme concentration showed a linearity. Studies of the enzyme inhibition by sodium azide, sodium diethyldithiocarbamate, thiourea, demonstrated that the active site of the enzyme contains a metal. The enzymatic discoloration of betanin is followed by the oxygen uptake.