Cloning and Subcellular Localization of GalNAc Transferase

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1. We have obtained a cDNA clone of the human homologue of the UDP-N-acctylgalactosamine : polypeptide N-acetylgalactosaminyltransferase (GalNAc transferase). AcDNA sequence for human GalNAc transferase showed high homology with its bovine homelogue and was identical to human isozyme Tlthat was recently reported.2. Twenty-three residues peptide was synthesized based on the obtained cDNA sequence and a mouse monoclonal antibody to the peptide (GNT-1) was successfully produced.3. GNT-1 reacted with ductal epithelial cells of the exocrine organs including pancreas, salivary gland, bronchial gland, and mammary gland. Oherewise, GNT-1 had no reactivity with mucus cells of salivary gland and stomach. These results suggest that ductal epithelial cells and mucus cells have different types of GalNAc transferase. It was noteworthy that parietal cells of stomach and a large number of cells in Langerhans islands of pancreas showed nice reactivity with GNT-1, suggesting these cells produce O-glycosylated protein except for mucin.4. Western immunoblotting with GNT-1 showed that the expression of GalNAc transferase T1 varies not only among organ types and cell type, but also according to cell differentiation.5.Based on the results deceribed above, we plan to study the expression of GalNAc transferase T1 in various kinds of gastrointstinal disease and produce a monoclonal antibody to GalNAc transferase T2