Protein methylases in hepatomas.

Abstract

The levels of various protein: S -adenosyl-l-methionine methyltransferases have been examined in solid hepatomas with varying rates of growth. Protein methylase I (protein-arginine: S -adenosyl-l-methionine methyltransferase) activity in tumors roughly paralleled the growth rate. The enzyme activity in the host liver was significantly elevated in the animals bearing both a slow-growing and a fast-growing hepatoma but otherwise remained in the normal range. Protein methylase II (protein-carboxyl: S -adenosyl-l-methionine methyltransferase) activity in both tumors and host livers showed no significant changes from normal rat liver. The protein methylase III (protein-lysine: S -adenosyl-l-methionine methyltransferase) activity in the tumors was about the same as in the host livers, except in the fast-growing Novikoff hepatoma in which the enzyme activity was increased 2- to 3-fold.