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O-GlcNAc transferase is part of a dynamic competition for a serine or threonine hydroxyl functional group in a peptide unit. Figure 3 shows an example of both reciprocal same-site occupancy and adjacent-site occupancy. For the same-site occupancy, OGT competes with kinase to catalyze the glycosylation of the protein instead of phosphorylation ...
GlcNAc moiety shown in red. O-GlcNAc (short for O-linked GlcNAc or O-linked β-N-acetylglucosamine) is a reversible enzymatic post-translational modification that is found on serine and threonine residues of nucleo cytoplasmic proteins. The modification is characterized by a β-glycosidic bond between the hydroxyl group of serine or threonine ...
Two conserved enzymes control this glycosylation of serine and threonine: O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). While OGT catalyzes the addition of O-GlcNAc to serine and threonine, OGA catalyzes the hydrolytic cleavage of O-GlcNAc from post-transitionally modified proteins. [14] OGA is a member of the family of hexosaminidases ...
O-linked glycosylation is the attachment of a sugar molecule to the oxygen atom of serine (Ser) or threonine (Thr) residues in a protein. O-glycosylation is a post-translational modification that occurs after the protein has been synthesised. In eukaryotes, it occurs in the endoplasmic reticulum, Golgi apparatus and occasionally in the ...
Glycosylation is a form of co-translational and post-translational modification. Glycans serve a variety of structural and functional roles in membrane and secreted proteins. [2] The majority of proteins synthesized in the rough endoplasmic reticulum undergo glycosylation. Glycosylation is also present in the cytoplasm and nucleus as the O ...
Oligosaccharyltransferase or OST (EC 2.4.1.119) is a membrane protein complex that transfers a 14- sugar oligosaccharide from dolichol to nascent protein. It is a type of glycosyltransferase. The sugar Glc 3 Man 9 GlcNAc 2 (where Glc= Glucose, Man= Mannose, and GlcNAc= N -acetylglucosamine) is attached to an asparagine (Asn) residue in the ...
Most glycosyltransferase enzymes form one of two folds: GT-A or GT-B. Glycosyltransferases (GTFs, Gtfs) are enzymes that establish natural glycosidic linkages.They catalyze the transfer of saccharide moieties from an activated nucleotide sugar (also known as the "glycosyl donor") to a nucleophilic glycosyl acceptor molecule, the nucleophile of which can be oxygen- carbon-, nitrogen-, or sulfur ...
Structure of human galectin-9 in complex with N-acetyllactosamine dimer, clearly showing the two carbohydrate binding sites. Galectins are a class of proteins that bind specifically to β-galactoside sugars, such as N-acetyllactosamine (Galβ1-3GlcNAc or Galβ1-4GlcNAc), which can be bound to proteins by either N-linked or O-linked glycosylation.