Catalyzes the transfer of sulfate to position 4 of non-reducing N-acetylgalactosamine (GalNAc) residues in both N-glycans and O-glycans. Participates in biosynthesis of glycoprotein hormones lutropin and thyrotropin, by mediating sulfation of their carbohydrate structures. Has a higher activity toward carbonic anhydrase VI than toward lutropin. Only active against terminal GalNAcbeta1,GalNAcbeta. Isoform 2, but not isoform 1, is active toward chondroitin.
Highly expressed in trachea. Also expressed in fetal lung, adult pancreas, testis and salivary gland. Expressed at low level in pituitary gland, apex of the heart, adult lung, prostate and mammary gland. Weakly or not expressed in heart, liver and spinal cord.