CHST6 catalyzes the transfer of sulfate to position 6 of non-reducing N-acetylglucosamine (GlcNAc) residues of keratan. It mediates sulfation of keratan in cornea. Keratan sulfate plays a central role in maintaining corneal transparency. CHST6 acts on the non-reducing terminal GlcNAc of short and long carbohydrate substrates that have poly-N-acetyllactosamine structures.