Enables acetylgalactosaminyltransferase activity. Acts upstream of or within chondroitin sulfate proteoglycan biosynthetic process. Predicted to be located in Golgi cisterna membrane. Predicted to be integral component of membrane. Is expressed in articular cartilage. Orthologous to human CSGALNACT2 (chondroitin sulfate N-acetylgalactosaminyltransferase 2). [provided by Alliance of Genome Resources, Apr 2022]