Component of the GPI transamidase complex. Essential for transfer of GPI to proteins, particularly for formation of carbonyl intermediates. Glycolipid biosynthesis; glycosylphosphatidylinositol-anchor biosynthesis. Forms a complex with PIGK/GPI8, PIGT, PIGU and GAA1. The disease is caused by variants affecting the gene represented in this entry. Belongs to the PIGS family.