The acceptor substrate specificity of porcine submaxillary UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase is dependent on the amino acid sequences adjacent to serine and threonine residues.

摘要: The acceptor substrate specificity of a pure polypeptide N-acetylgalactosaminyltransferase has been examined with synthetic polypeptides sequences identical, or similar to those found in porcine mucin human erythropoietin. adjacent either threonine serine markedly influence the formation GalNAc-O-Thr and GalNAc-O-Ser. Examination mucin-like peptide VLGXXAV, where X is Thr, Ser, Ala, shows only Thr-containing peptides be acceptors. best formed when XX TT. Peptides as AT TA are less effective ST TS much amino acids by residues 121-131 erythropoietin, PPDAASAAPLR, also Thus, PPDASSSAPLR PPDVVSVVPLR about 5- 30-fold, respectively, active than erythropoietin peptide. PPDGGSGGPLR inactive. shorter DAASAAPL 5-fold full-length peptide, but AASAA These studies indicate that one transferase can form both GalNAc-O-Ser glycosylated residue proper kind. contrast earlier suggestions, there no evidence different transferases GalNAc-O-Thr. tissue homogenates from various tissues confirms this conclusion.