Tyrosinase activity in serum from normal and melanoma-bearing mice.

Tyrosinase activity was demonstrated in the sera from melanoma-bearing mice. One, two, and three weeks following tumor transplantation, 12, 80, and 90% of the respective sera from these mice showed positive results. No sera from normal mice had tyrosinase activity. There was a correlation between tumor size and tyrosinase activity, the coefficient of correlation being 0.71. The activity in the serum had the characteristics of an enzymic reaction, and the cofactor requirements were similar to those described for tyrosinase from melanoma tissue. The serum tyrosinase was found to be soluble.