Figure 1.

Human enzymes using dolichol-linked donor substrates. The official protein symbols (www.genames.org) of all known human enzymes are indicated. PIG (phosphatidylinositol glycan anchor) enzymes generate the GPI (glycosylphosphatidylinositol)anchor. ALG (asparagine-linked glycosylation) enzymes transfer four mannoses and three glucoses to the lipid-linked oligosaccharide before it is transferred to proteins by the oligosaccharyltransferase complex. STT3 (staurosporine- and temperature-sensitive) is the catalytic subunit of the oligosaccharyltransferase and occurs in two forms. Two POMTs (protein O-mannosyltransferases) and four TMTC (transmembrane and tetratricopeptide repeat containing) proteins transfer O-mannose to protein. Finally, four homologues of the Caenorhaditis elegans C-mannosyltransferase DPY-19 are present in human.