Transfers N-acetylgalactosamine onto carbohydrate substrates. Involved in susceptibility to pore-forming crystal toxins in conjunction with bre-1, bre-3, bre-4, and bre-5. Involved in resistance to the nematotoxic C.cinerea galectin Cgl2. Protein modification; protein glycosylation. Belongs to the glycosyltransferase 31 family.