InterPro: IPR003342 Glycosyl transferase, family 39

The biosynthesis of disaccharides, oligosaccharides and polysaccharides involves the action of hundreds of different glycosyltransferases. These enzymes catalyse the transfer of sugar moieties from activated donor molecules to specific acceptor molecules, forming glycosidic bonds. A classification of glycosyltransferases using nucleotide diphospho-sugar, nucleotide monophospho-sugar and sugar phosphates (EC:2.4.1.-) and related proteins into distinct sequence based families has been described [1]. This classification is available on the CAZy (CArbohydrate-Active EnZymes) web site [2]. The same three-dimensional fold is expected to occur within each of the families. Because 3-D structures are better conserved than sequences, several of the families defined on the basis of sequence similarities may have similar 3-D structures and therefore form 'clans'.

Dolichyl-phosphate-mannose-protein mannosyltransferase proteins EC:2.4.1.109 belong to the glycosyltransferase family 39 (GT39) and are responsible for O-linked glycosylation of proteins. They catalyse the reaction:

Dolichyl phosphate D-mannose + protein -> dolichyl phosphate + O-D-mannosyl-protein.

The transfer of mannose to seryl and threonyl residues of secretory proteins is catalyzed by a family of protein mannosyltransferases in Saccharomyces cerevisiae coded for by seven genes (PMT1-7). Protein O-glycosylation is essential for cell wall rigidity and cell integrity and this protein modification is vital for S. cerevisiae [3].