원문정보
초록
영어
More than 60% of the currently available therapeutic proteins are glycoproteins attached with glycans, which play important roles in the protein folding, therapeutic efficacy, in vivo half-life, and immune reactions. Our group has focused on N-glycosylation pathway engineering of recombinant expression hosts including yeasts and Chinese hamster ovary (CHO) cells for production of therapeutic glycoproteins with improved potency. Different engineering strategies are required depending on the classes of therapeutic proteins because their optimal glycan structures are different. Many therapeutic enzymes used for treatment of lysosomal storage diseases require high contents of mannose-6- phosphate (M-6-P) glycan, which is essential for cellular uptake and targeting to lysosomes. Although yeasts do not have M-6-P glycans, they have some glycans containing mannosylphosphorylated mannose residues which can be converted to M-6-P structure through removal of the outer capping mannose. Recently, we constructed a glyco-engineered Saccharomyces cerevisiae mnn1Δoch1Δ strain overexpressing YlMPO1 gene, which was shown to have very high content of mannosylphosphorylated glycans [1, 2]. As they were efficiently converted to high content of M-6-P glycans through uncapping process, our engineering strategy showed a promise for production of biobetter enzymes with enhanced lysosomal targeting capabilities. For prolonged in vivo half-life of glycoproteins, sialic acids present on non-reducing terminal of glycan are important. We compared several bacterial α(2,6)-sialyltransferases and found that they have inherent siallidase activities, which decreased the amount of sialylated products [3]. These sialidase activities were inhibited by simple treatment of alkaline phosphatase, which desphosphorylates free cytidine monophosphate (CMP) generated from a donor substrate (CMP-N-acetylneuraminic acid) during the sialyltransferase reaction. It greatly enhanced the efficiency of bacterial α(2,6)- sialyltransferase reaction, which resulted in the increased content of bi-sialylated N-glycan up to ~98% without any decrease in prolonged reactions. Our efforts to construct Chinese hamster ovary (CHO) cells for production of glycoproteins with increased content of sialic acids shall be introduced also.