Part of the glycosylphosphatidylinositol-N-acetylglucosaminyltransferase (GPI-GnT) complex that catalyzes the transfer of N-acetylglucosamine from UDP-N-acetylglucosamine to phosphatidylinositol and participates in the first step of GPI biosynthesis. Glycolipid biosynthesis; glycosylphosphatidylinositol-anchor biosynthesis. Component of the glycosylphosphatidylinositol-N-acetylglucosaminyltransferase (GPI-GnT) complex composed at least by PIGA, PIGC, PIGH, PIGP, PIGQ, PIGY and DPM2. Interacts with PIGQ. Belongs to the PIGH family.