GPI anchor - Definition

A GPI anchor (phosphatidyl-inositol glycane) is a common modification of the C terminus of membrane attached proteins in which a hydrophobic phosphatidyl inositol moiety is linked through glucosamine and mannose to a phosphoryl ethanolamine residue that is linked to the C terminal amino acid of the protein by its amino group. The modification is added in the endoplamsic reticulum to a protein after its synthesis. The two fatty acids within the hydrophobic inositol group anchors the protein to the exterior leaflet of the membrane. Since the glypiation is the sole means of attachment of such proteins to the membrane, cleavage of the group by phospholipases will result in controlled release of the protein from the membrane.

Defects of GPI anchors occur in the rare disease paroxysmal nocturnal hemoglobinuria.