PER1 is required for GPI-phospholipase A2 activity and is involved in lipid remodelling of GPI-anchored proteins []. PER1 is part of the CREST superfamily []. Human PERLD1 is a functional homologue of PER1, and is also known as PGAP3. Mutations in PGAP3 cause hyperphosphatasia with mental retardation syndrome [].