Membrane glycoprotein biosynthesis: Changes in levels of glycosyl transferases in fibroblasts transformed by oncogenic viruses

Fibroblasts transformed by oncogenic viruses were found to have greater enzymic activities of four membrane glycoprotein:glycosyl transferases on a cell or protein basis then two non‐transformed fibroblastic lines. These enzymes are responsible for the synthesis of membrane glycoproteins; each of the four transferases studied, the polypeptide:N‐acetylgalactosaminyl, glycoprotein:galactosyl, fetuin:fucosyl and PSM:fucosyl transferases, was more than twice as active in the transformed cell lines using both endogenous and added receptor. The most pronounced differences occurred with the doubly (SV‐PY‐3T3) transformed fibroblasts in all cases; with the N‐acetylgalactosaminyl and galactosyl transferases the increase was 8–16 fold over the non‐transformed cells. It was demonstrated that these results do not arise from a changed level of glycosidase activities.