Molecular cloning and expression of two distinct human N-acetylgalactosamine 4-O-sulfotransferases that transfer sulfate to GalNAcβ1→4GlcNAcβ1→R in both N- and O-glycans

Recently, cDNAs encoding human chondroitin 4-O-sulfotransferase-1 and -2 (C4ST-1 and C4ST-2) were cloned based on their similarity to HNK-1 sulfotransferase (HNK-1ST) (Hiraoka, N., Nakagawa, H., Ong, E., Akama, T,O., Fukuda, M,N., and Fukuda, M. [2000] Molecular cloning and expression of two distinct human chondroitin 4-O-sulfotransferases that belong to the HNK-1 sulfotransferase gene family. J. Biol. Chem., 275, 20188-20196), In the present study, we identified two additional novel sulfotransferases by searching the expression sequence tag and genomic DNA database for enzymes similar to C4ST-1 and C4ST-2. These newly cloned enzymes, termed GalNAc4ST-1 and GalNAc4ST-2, belong to the HNK-1ST gene family having 40-42% identity with C4ST-1. GalNAc4ST-1 and -2 do not add sulfate to HNK-1 precursor glycans, chondroitin, or desulfated dermatan sulfate. Instead, both enzymes can transfer sulfate to the 4-position of GalNAc in the context of GalNAc-beta1 --> 4GlcNAc beta1 -->R attached to both N-linked and core 2 branched O-linked oligosaccharides. GalNAc4ST-1 and -2 transcripts are highly expressed in the pituitary gland and trachea, respectively, and GalNAc4ST-1 and -2 transcripts are reciprocally expressed in other tissues as well, Moreover, both enzymes can transfer sulfate to lutropin, a pituitary glycoprotein hormone, These combined results indicate that GalNAc4ST-1 and -2 play critical roles in forming sulfo --> 4GalNAc beta1 --> 4GlcNAc beta1 -->R in both N-glycans and O-glycans in a tissue-specific manner.