Tyrosinase activity and isozymes in B-16 mouse melanomas

B-16 melanomas grown for 13 and 22 days after transplantation in mice were utilized in studies of subcellular distribution of tyrosinase activity and tyrosinase isozyme patterns. The tyrosinase activity utilizing L-tyrosine-14-C was higher in the younger than in the older melanomas. The percent of total activity distributed in the 144,000 g supernatant was 38% for the former and 46% for the latter. Both melanomas had higher percentage of activity confined in the pellet obtained by centrifuging the crude homogenate at 600 g. The digestion of P 600 g pellet by lipase liberated tyrosinase activity which was two fold of the activity originally counted in the pellet. Five isozymes wereobserved in the soluble tyrosinase and two in the solubilized tyrosinase.