Essential for GPI-anchoring of precursor proteins but not for GPI synthesis. Acts before or during formation of the carbonyl intermediate. Glycolipid biosynthesis; glycosylphosphatidylinositol-anchor biosynthesis. Forms a complex with PIGK/GPI8, PIGT, PIGU and PIGS. Ubiquitously expressed in fetal and adult tissues. Expressed at higher levels in fetal tissues than adult tissues. In embryos abundant in the choroid plexus, skeletal muscle,.