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. a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol) + an N-(2R-hydroxy-very-long-chain fatty acyl)-(R)-4-hydroxysphingoid base = a 1,2-diacyl-sn-glycerol + a 1D-myo-inositol-1-phospho-N-[(R)-2-hydroxy-very-long-chain fatty acyl]-(R)-4-hydroxysphingoid base Inhibited by aureobasidin A (AbA), khafrefungin and rustmicin. Component of the inositol phosphorylceramide synthase complex composed of at least AUR1 and KEI1. Present with 4170 molecules/cell in log phase SD medium. Belongs to the AUR1 family.