Disclosed herein are genetically modified microorganisms and related methods for the enhanced production and export of oligosaccharides. The microorganisms described herein express major facility superfamily proteins such as CDT-1, which allows for the export of oligosaccharides. Variants of CDT-1 exhibit higher activity regarding oligosaccharide export. The microorganisms described herein express formation enzymes for the production of oligosaccharides. Means to export oligosaccharides into the growth medium are provided herein.

The present invention relates to cell lines that are genetically modified to overexpress a β-galactoside α-2,3-sialyltransferase 1 (ST3Gal1), preferably human ST3Gal1, which can be used for the production of recombinant glycoproteins having highly or fully sialylated O-linked GalNAc glycans (GalNAc O-glycans), preferably core 1 GalNAc O-glycans, as well as to respective recombinant glycoproteins. Further, the present invention relates to respective methods of expressing recombinant glycoproteins, methods of increasing the degree of sialylation of recombinant glycoproteins, and methods of decreasing the micro-heterogeneity of GalNAc O-glycans. Finally, the present invention relates to respective uses of the above cell lines for the production of recombinant glycoproteins, for increasing the degree of sialylation of recombinant glycoproteins, and for decreasing the micro-heterogeneity of O-linked GalNAc glycans of recombinant glycoproteins.

This disclosure relates to glycoengineering, and methods of utilizing glycoengineering for various therapeutic purposes.

The purpose of the present invention is to provide a novel monoclonal antibody having high affinity and that strictly recognizes, as a sugar chain epitope, only a “Siaα2,6Galβ1,4GlcNAc (6′-Sialyl-LacNAc): CDw75” sugar chain structure, being a molecular target for diagnosis of the malignancy of tumors. An anti-CDw75 monoclonal antibody is provided that recognizes “CDw75” sugar chain structures but does not recognize similar sugar chain structures indicated by “Galβ1,4GlcNAc”, “Siaα2,3Galβ1,4GlcNAc”, or “Siaα2,6Galβ1,4Glc”, by using a glycolipid antigen bonding a carrier lipid compound “HOCH.sub.2CH(NH—CO—(CH.sub.2).sub.22—CH.sub.3)—(CH.sub.2).sub.9—CH.sub.3 (C12L)” developed by the inventors to a “CDw75” sugar chain. The obtained anti-CDw75 monoclonal antibody is an excellent detection drug for B-cell lymphoma, gastric cancer, or colorectal cancer, an excellent diagnostic agent for tumor malignancy, etc., an excellent treatment agent for B-cell lymphoma, gastric cancer, or colorectal cancer, and an excellent prevention/treatment drug for influenza.

The present disclosure is directed to the properties of certain glycosyltransferase variants having N-terminal truncation deletions or internal deletions. Any of the mutants disclosed in here exhibit α-2,6-sialyltransferase enzymatic activity in the presence of CMP-activated sialic acid as co-substrate, and in the presence of a suitable acceptor site. A fundamental finding documented in the present disclosure is that suchs enzyme are not only capable of catalyzing transfer of a sialidyl moiety but they are also capable of catalyzing hydrolytic cleavage of terminally bound sialic acid from a glycan.

The present invention provides novel methods for preparing glycosylated molecules such as oligosaccharides, glycolipids, and glycoproteins/peptides. Novel sialyltransferases are also disclosed. The method includes forming a reaction mixture containing an acceptor molecule, a donor substrate having a sugar moiety and a nucleotide, and a sialyltransferase selected from PmST3 (SEQ ID NO:7) and certain variants thereof. The reaction mixture is formed under conditions sufficient to transfer the sugar moiety from the donor substrate to the acceptor molecule, thereby forming the glycosylated molecule. In some embodiments, the acceptor molecule is selected from a natural product, an oligosaccharide, a glycoprotein, and a glycolipid. In some embodiments, the donor substrate is formed via conversion of a suitable hexosamine derivative to a cytidine 5′-monophosphate(CMP)-sialic acid in a one-pot reaction mixture containing asialic acid aldolase and a CMP-sialic acid synthetase.

The present invention relates to the production of steviol glycoside rebaudiosides D4, WB1 and WB2 and the production of rebaudioside M from Reb D4.

[Problem to be Solved]

The importance of sugar chains having α2,3- or α2,6-linked sialic acid at their non-reducing ends is known. Industrial production has been demanded for these sugar chain compounds. Particularly, the production of glycoprotein drugs or the like inevitably requires producing in quantity sugar chains having homogeneous structures by controlling the linking pattern (α2,6-linkage or α2,3-linkage) of sialic acid. Particularly, a triantennary or tetraantennary N-type complex sugar chain having sialic acid at each of all non-reducing ends is generally considered difficult to chemically synthesize. There has been no report disclosing that such a sugar chain was chemically synthesized. Furthermore, these sugar chains are also difficult to efficiently prepare enzymatically.

[Solution]

The present inventors have newly found the activity of sialyltransferase of degrading sialic acid on a reaction product in the presence of CMP and also found that formed CMP can be degraded enzymatically to thereby efficiently produce a sialic acid-containing sugar chain. The present inventors have further found that even a tetraantennary N-type sugar chain having four α2,6-linked sialic acid molecules, which has previously been difficult to synthesize, can be prepared at high yields by one-pot synthesis comprising the elongation reaction of a biantennary sugar chain used as a starting material without performing purification after each enzymatic reaction.

Provided herein are host cells capable of producing hybrid oligosaccharides and polysaccharides, wherein said hybrid oligosaccharides and polysaccharides do not comprise a hexose at the reducing end of their first repeat unit. Also provided herein are hybrid oligosaccharides or polysaccharides and bioconjugates which can be produced by the host cells described herein, wherein said bioconjugates comprise a carrier protein linked to a hybrid oligosaccharide or polysaccharide that does not comprise a hexose at the reducing end of its first repeat unit.

The present disclosure is directed to the use of certain glycosyltransferase variants having N-terminal truncation deletions. Contrary to previous findings certain truncations were found to exhibit sialidase enzymatic activity, particularly a variant of human sialyltransferase (hST6Gal-I) with a truncation deletion involving the first 89 N-terminal amino acids of the respective wild-type polypeptide. A fundamental finding documented in the present disclosure is that there exists a variant of this enzyme which is capable of catalyzing transfer of a glycosyl moiety as well as hydrolysis thereof. Thus, disclosed is a specific exemplary variant of mammalian glycosyltransferase, nucleic acids encoding the same, methods and means for recombinantly producing the variant of mammalian glycosyltransferase and use thereof, particularly for sialylating in a quantitatively controlled manner terminal acceptor groups of glycan moieties being part of glycoproteins such as immunoglobulins.