This enzyme is also active when O-4 of the glucosamine is substituted by carrying the oligosaccharide that can link a protein to the structure. It therefore cleaves proteins from the lipid part of the glycosylphostphatidylinositol (GPI) anchors. In some cases, the long-chain acyl group at the sn-1 position of glycerol is replaced by an alkyl or alk-1-enyl group. In other cases, the diacylglycerol is replaced by ceramide (see Lip-1.4
for definition). The only characterized enzyme with this specificity is from Trypanosoma brucei, where the acyl groups are myristoyl, but the function of the trypanosome enzyme is unknown. Substitution on O-2 of the inositol blocks action of this enzyme. It is not identical with EC 18.104.22.168, glycosylphosphatidylinositol phospholipase D.