PIGA (Homo sapiens): Phosphatidylinositol N-acetylglucosaminyltransferase subunit A; Necessary for the synthesis of N-acetylglucosaminyl- phosphatidylinositol, the very early intermediate in GPI-anchor biosynthesis; Belongs to the glycosyltransferase group 1 family. Glycosyltransferase 4 subfamily.