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. The disease is caused by variants affecting the gene represented in this entry. Erroneous prediction from an unspliced cDNA.