Catalysis of the reaction: 6-(alpha-D-glucosaminyl)-1-phosphatidyl-1D-myo-inositol = 1,2-diacyl-sn-glycerol + 6-(alpha-D-glucosaminyl)-1D-myo-inositol 1,2-cyclic phosphate.
glycosylphosphatidylinositol-specific phospholipase C activity