Catalytic component of the inositol phosphorylceramide synthase which catalyzes the addition of a phosphorylinositol group onto ceramide to form inositol phosphorylceramide, an essential step in sphingolipid biosynthesis. Inhibited by aureobasidin A (AbA). Component of the inositol phosphorylceramide synthase complex composed of at least aur1 and kei1. Belongs to the AUR1 family.