Catalyzes the transfer of sulfate to position 6 of galactose residues of keratan. It has a preference for sulfating keratan sulfate, but it also transfers sulfate to the unsulfated polymer. The sulfotransferase activity on sialyl LacNAc structures is much higher than the corresponding desialylated substrate, and only internal galactose residues are sulfated. It also may function in the sulfation of sialyl N-acetyllactosamine oligosaccharide chains attached to glycoproteins. It participates in biosynthesis of selectin ligands. Selectin ligands are present in high endothelial cells (HEVs) and play a central role in lymphocyte homing at sites of inflammation. 
Aggrecan is the major proteoglycan of human articular cartilage. The core protein is substituted by a number of keratan sulfate and chondroitin sulfate glycosaminoglycan chains. Whereas chondroitin sulfate is widely distributed throughout the body, keratan sulfate is primarily expressed in cartilage (joints, trachea, intervertebral discs) and cornea.