phosphatidyl-myo-inositol mannosyltransferase. This family is most closely related to the GT4 family of glycosyltransferases and named after PimA in Propionibacterium freudenreichii, which is involved in the biosynthesis of phosphatidyl-myo-inositol mannosides (PIM) which are early precursors in the biosynthesis of lipomannans (LM) and lipoarabinomannans (LAM), and catalyzes the addition of a mannosyl residue from GDP-D-mannose (GDP-Man) to the position 2 of the carrier lipid phosphatidyl-myo-inositol (PI) to generate a phosphatidyl-myo-inositol bearing an alpha-1,2-linked mannose residue (PIM1). 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.

family 4 and family 28 glycosyltransferases similar to Klebsiella WabH. 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.

capsular polysaccharide biosynthesis glycosyltransferase CapM and similar proteins. This family is most closely related to the GT4 family of glycosyltransferases. CapM in Staphylococcus aureus is required for the synthesis of type 1 capsular polysaccharides.

glycosyltransferase ExpE7 and similar proteins. This family is most closely related to the GT4 family of glycosyltransferases. ExpE7 in Sinorhizobium meliloti has been shown to be involved in the biosynthesis of galactoglucans (exopolysaccharide II).

amylovoran biosynthesis glycosyltransferase AmsD and similar proteins. This family is most closely related to the GT4 family of glycosyltransferases. AmSD in Erwinia amylovora has been shown to be involved in the biosynthesis of amylovoran, the acidic exopolysaccharide acting as a virulence factor. This enzyme may be responsible for the formation of galactose alpha-1,6 linkages in amylovoran.