Glycan engineering of proteins with whole living yeast cells expressing rat liver alpha 2,3-sialytransferase in the porous cell wall

The N-glycans of recombinant proteins produced via the secretory pathway of cultured mammalian cells are often undersialylated, and insect cells lack sialytransferases. Undersialylated glycoproteins are rapidly cleared from t he circulation, compromising the effect of pharmaceuticals. We show that in cubation with living Saccharomyces cerevisiae cells expressing the catalyti c ectodomain of rat liver alpha 2,3-sialyltransferase (ST3N(e)) in the poro us cell wall resulted in sialylation of glycoproteins. The K-m values of th e yeast enzyme for several substrates were similar to those of recombinant ST3N(e) from insect cells and of authentic ST3N, The yeast strain provides an inexpensive self-perpetuating source of ST3N activity for glycan enginee ring of recombinant proteins. (C) 1998 Federation of European Biochemical S ocieties.