We have previously cloned chondroitin-4-sulfotransferase (C4ST) cDNA from mouse brain. In this paper, we report cloning and characterization of GalNAc 4-sulfotransferase (GalNAc4ST), which transfers sulfate to position 4 of the nonreducing terminal GalNAc residue. The obtained cDNA contains a single open reading frame that predicts a type II transmembrane protein composed of 424 amino acid residues. Identity of the amino acid sequence between GalNAc4ST and human C4ST was 30%. When the cDNA was transfected in COS-7 cells, sulfotransferase activity toward carbonic anhydrase VI was overexpressed but no sulfotransferase activity toward chondroitin or desulfated dermatan sulfate was increased over the control. Sulfation of carbonic anhydrase VI by the recombinant GalNAc4ST occurred at position 4 of the GalNAc residue of N-linked oligosaccharides. The recombinant GalNAc4ST transferred sulfate to position 4 of GalNAc residue of p-nitrophenyl GalNAc, indicating that this sulfotransferase transfers sulfate to position 4 at the nonreducing terminal GalNAc residue. Dot blot analysis showed that the message of GalNAc4ST was expressed strongly in the human pituitary, suggesting that the cloned GalNAc4ST may be involved in the synthesis of the nonreducing terminal GalNAc 4-sulfate residues found in the N-linked oligosaccharides of pituitary glycoprotein hormones.Sulfated sugar chains are found not only in glycosaminoglycans but also in oligosaccharides of glycoproteins and glycolipids (1). Sulfate moieties attached to the sugar residues of glycosaminoglycans and oligosaccharides play key roles in various molecular and cellular interactions: binding of FGF2 to heparan sulfate (2, 3); interaction of L-selectin on the lymphocytes with L-selectin ligands on the endothelial cells of high endothelial venule (4 -10); binding of HNK-1 epitope to the sulfoglucuronyl carbohydrate-binding protein (11); and rapid clearance of a pituitary glycoprotein hormone, lutropin, mediated by the interaction with a hepatic reticuloendothelial cell receptor (12, 13). Various sulfotransferases involved in the sulfation of glycosaminoglycans (14) and oligosaccharides (15-17) have been cloned. We have purified and cloned chondroitin-6-sulfotransferase (C6ST) 1 (18, 19) and chondroitin-4-sulfotransferase (C4ST) (20, 21), which are involved in the sulfation of position 6 and position 4, respectively, of GalNAc residues of chondroitin. C6ST also transfers sulfate to position 6 of Gal residue of keratan sulfate and sialyl N-acetyllactosamine oligosaccharides (22, 23). We have cloned keratan sulfate Gal-6-sulfotransferase using the homology with C6ST. Keratan sulfate Gal6ST transfers sulfate to position 6 of the Gal residue of keratan sulfate and sialyl N-acetyllactosamine oligosaccharides but not to GalNAc residue of chondroitin (24,25). Several GlcNAc-6-sulfotransferases, which are involved in the synthesis of 6-sulfo-sialyl Lewis x, have been cloned from the family genes including C6ST and keratan sulfate Gal6ST (9,10,26). On the other hand, C4ST showed s...