Probable acetyltransferase, which acetylates the inositol ring of phosphatidylinositol during biosynthesis of GPI-anchor. Acetylation during GPI-anchor biosynthesis is not essential for the subsequent mannosylation and is usually removed soon after the attachment of GPIs to proteins. Glycolipid biosynthesis; glycosylphosphatidylinositol-anchor biosynthesis. Target of the antifungal compound 1-[4-butylbenzyl]isoquinoline that inhibits cell wall localization of GPI-anchored mannoproteins. Belongs to the PIGW family.