This family consists of several eukaryotic dolichol phosphate-mannose biosynthesis regulatory (DPM2) proteins. Biosynthesis of glycosylphosphatidylinositol and N-glycan precursor is dependent upon a mannosyl donor, dolichol phosphate-mannose (DPM). DPM2, an 84 amino acid membrane protein expressed in the endoplasmic reticulum (ER), makes a complex with DPM1 that is essential for the ER localisation and stable expression of DPM1. Moreover, DPM2 enhances binding of dolichol phosphate, a substrate of DPM synthase. Biosynthesis of DPM in mammalian cells is regulated by DPM2 [].
This family belongs to glycosyltransferase 2 superfamily and consists of proteins similar to eukaryotic DPM1, including enzymes from bacteria and archaea.DPM1 is the catalytic subunit of eukaryotic dolichol-phosphate mannose (DPM) synthase. DPM synthase is required for synthesis of the glycosylphosphatidylinositol (GPI) anchor, N-glycan precursor, protein O-mannose, and C-mannose. In higher eukaryotes,the enzyme has three subunits, DPM1, DPM2 and DPM3. DPM is synthesized from dolichol phosphate and GDP-Man on the cytosolic surface of the ER membrane by DPM synthase and then is flipped onto the luminal side and used as a donor substrate []. In Saccharomyces cerevisiae and Trypanosoma brucei, DPM synthase consists of a single component (Dpm1p and TbDpm1, respectively) that possesses one predicted transmembrane region near the C terminus for anchoring to the ER membrane. In contrast, the Dpm1 homologues of fission yeast, fungi, and animals, have no transmembrane region, suggesting the existence of adapter molecules for membrane anchoring [].Polyprenol monophosphomannose synthase (Ppm1) also belongs to this family. Ppm1 is a bifunctional protein that transfers mannose from GDP-mannose to lipid acceptors to form polyprenol monophosphomannose (PPM), which acts as a sugar donor for lipoglycan synthesis in mycobacteria [].
