Glycosyl transferases group 1. Mutations in this domain of human PIGA lead to disease (Paroxysmal Nocturnal haemoglobinuria). Members of this family transfer activated sugars to a variety of substrates, including glycogen, Fructose-6-phosphate and lipopolysaccharides. Members of this family transfer UDP, ADP, GDP or CMP linked sugars. The eukaryotic glycogen synthases may be distant members of this family.

This family is most closely related to the GT1 family of glycosyltransferases. WabH in Klebsiella pneumoniae has been shown to transfer a GlcNAc residue from UDP-GlcNAc onto the acceptor GalUA residue in the cellular outer core.

This family is most closely related to the GT1 family of glycosyltransferases. wbaZ in Salmonella enterica has been shown to possess the mannosyl transferase activity. The members of this family are found in certain bacteria and Archaea.

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. ALG2, a 1,3-mannosyltransferase, in yeast catalyzes the mannosylation of Man(2)GlcNAc(2)-dolichol diphosphate and Man(1)GlcNAc(2)-dolichol diphosphate to form Man(3)GlcNAc(2)-dolichol diphosphate. A deficiency of this enzyme causes an abnormal accumulation of Man1GlcNAc2-PP-dolichol and Man2GlcNAc2-PP-dolichol, which is associated with a type of congenital disorders of glycosylation (CDG), designated CDG-Ii, in humans.