Studies on the surface properties of hybrid cells. II. Sialyl-transferase activity on the surface of malignant and non-malignant cells.

A measurable surface activity of sialyl-transferase is demonstrated by a number of different methods to exist on the plasma membranes of both malignant and non-malignant cells. The amount of enzyme present on the surface of malignant cells is found to be higher than that on the non-malignant ones in a wide range of malignant and non-malignant cell lines. It is proposed that the difference in apparent activity results in part from the presence of incomplete glycoproteins in the surface membranes of the malignant cells and in part from an increased rate of membrane synthesis in these cells.