Phosphatidylinositol Glycan Z (PIGZ)

PIGZ encodes a protein that is localized to the endoplasmic reticulum, and is involved in GPI anchor biosynthesis. As shown for the yeast homolog, which is a member of a family of dolichol-phosphate-mannose (Dol-P-Man)-dependent mannosyltransferases, this protein can also add a side-branching fourth mannose to GPI precursors during the assembly of GPI anchors.The deduced 579-amino acid protein shares 30% amino acid identity with the S. cerevisiae Smp3 ortholog. Immunocytochemical studies localized PIGZ to the endoplasmic reticulum in HeLa cells. Dot-blot analysis detected PIGZ in most human tissues with highest levels in adult and fetal brain, especially in cerebellum, as well as in transverse colon, descending colon, and rectum, but expression was nearly absent in cultured human cell lines.