Transfers N-acetylgalactosamine onto carbohydrate substrates (By similarity). Involved in susceptibility to pore-forming crystal toxins in conjunction with bre-1, bre-3, bre-4, and bre-5 (PubMed:12944392). Involved in resistance to the nematotoxic C.cinerea galectin Cgl2 (PubMed:20062796). Protein modification; protein glycosylation. Worms exhibit resistance to the Cry5B toxin produced by Bacillus thuringiensis. This is thought to be due to mutants having reduced population of glycolipids which are targeted by the Cry5B protein. Belongs to the glycosyltransferase 31 family.