Glycosyltransferases catalyze the transfer of sugar moieties from activated donor molecules to specific acceptor molecules, forming glycosidic bonds. The acceptor molecule can be a lipid, a protein, a heterocyclic compound, or another carbohydrate residue. The structures of the formed glycoconjugates are extremely diverse, reflecting a wide range of biological functions. The members of this family share a common GTB topology, one of the two protein topologies observed for nucleotide-sugar-dependent glycosyltransferases. GTB proteins have distinct N- and C- terminal domains each containing a typical Rossmann fold. The two domains have high structural homology despite minimal sequence homology. The large cleft that separates the two domains includes the catalytic center and permits a high degree of flexibility.

This family is most closely related to the GT1 family of glycosyltransferases. wlbH in Bordetella parapertussis has been shown to be required for the biosynthesis of a trisaccharide that, when attached to the B. pertussis lipopolysaccharide (LPS) core (band B), generates band A LPS.

PIGA (GPI anchor biosynthesis). This domain is found on phosphatidylinositol n-acetylglucosaminyltransferase proteins. These proteins are involved in GPI anchor biosynthesis and are associated with disease the paroxysmal nocturnal haemoglobinuria.

This family is most closely related to the GT1 family of glycosyltransferases and named after YqgM in Bacillus licheniformis about which little is known. Glycosyltransferases catalyze the transfer of sugar moieties from activated donor molecules to specific acceptor molecules, forming glycosidic bonds. The acceptor molecule can be a lipid, a protein, a heterocyclic compound, or another carbohydrate residue. This group of glycosyltransferases is most closely related to the previously defined glycosyltransferase family 1 (GT1). The members of this family may transfer UDP, ADP, GDP, or CMP linked sugars. The diverse enzymatic activities among members of this family reflect a wide range of biological functions. The protein structure available for this family has the GTB topology, one of the two protein topologies observed for nucleotide-sugar-dependent glycosyltransferases. GTB proteins have distinct N- and C- terminal domains each containing a typical Rossmann fold. The two domains have high structural homology despite minimal sequence homology. The large cleft that separates the two domains includes the catalytic center and permits a high degree of flexibility. The members of this family are found mainly in certain bacteria and archaea.

This family is most closely related to the GT1 family of glycosyltransferases. Phosphatidylinositol glycan-class A (PIG-A), an X-linked gene in humans, is necessary for the synthesis of N-acetylglucosaminyl-phosphatidylinositol, a very early intermediate in glycosyl phosphatidylinositol (GPI)-anchor biosynthesis. The GPI-anchor is an important cellular structure that facilitates the attachment of many proteins to cell surfaces. Somatic mutations in PIG-A have been associated with Paroxysmal Nocturnal Hemoglobinuria (PNH), an acquired hematological disorder.