The effect of cell concentration on alpha 2,3-sialyltransferase activity in attachment culture of a human erythropoietin-producing Chinese hamster ovary cell line

Terminal sialylation of therapeutic glycoprotein is important for biological activity and in vivo stability. The enzyme α2,3-sialyltransferase is the key enzyme that links sialic acids to the termini of glycans in the Chinese hamster ovary (CHO) cell line. Terminal sialylation is affected by numerous factors, but the elements that regulate α2,3-sialyltransferase are not known. We investigated the relationship between α2,3-sialyltransferase activity, ammonium concentration, and cell attachment area-based cell concentration in a recombinant human erythropoietin (rhEPO)-producing CHO cell line. We found that ammonium in the culture medium had almost no effect on α2,3-sialyltransferase activity, but that the activity was affected by cell attachment area-based cell concentration; α2,3-sialyltransferase activity and terminal sialylation of rhEPO decreased with increasing the cell concentration. These results demonstrate that the cell attachment area-based cell concentration is an important factor that affects 2,3-sialyltransferase activity and terminal sialylation of CHO cells.