Purification and characterization of a UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase specific for glycosylation of threonine residues.

摘要: A UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase from porcine submaxillary glands was purified to electrophoretic homogeneity. IgG prepared antisera against the pure enzyme immunoprecipitated transferase in Triton X-100 extracts of glands. The is a membrane-bound contrast bovine colostrum enzyme, which soluble absence detergents. Both transferases have similar properties but also differ significantly. Examination acceptor substrate specificity gland showed that it specifically transferred N-acetylgalactosamine UDP-GalNAc hydroxyl group threonine and devoid activity toward serine-containing peptides. These results imply more than one involved forming GalNAc-threonine GalNAc-serine linkages found O-linked oligosaccharides glycoproteins. amino acid sequence adjacent glycosylated residues may influence rate glycosylation by transferase. For example, second residue sequence, Thr-Thr, appears be about twice as fast first rapidly single, isolated residues. However, no unique consensus for evident, any accessible potential substrate.