Beta-1,4 N-acetylgalactosaminyltransferase 2 (EC 2.4.1.-) (Sd(a) beta- 1,4-GalNAc transferase) (UDP-GalNAc-Neu5Aca2-3Galb-R b1,4-N- acetylgalactosaminyltransferase); Involved in the synthesis of the Sd(a) antigen (Sia- alpha2,3-[GalNAc-beta1,4]Gal-beta1,4-GlcNAc), a carbohydrate determinant expressed on erythrocytes, the colonic mucosa and other tissues. Transfers a beta-1,4-linked GalNAc to the galactose residue of an alpha-2,3-sialylated chain (566 aa)