Incorporation of N-acetylgalactosamine into consecutive threonine residuesin MUC2 tandem repeat by recombinant human N-acetyl-D-galactosamine transferase-T1, T2 and T3

An oligopeptide containing three consecutive Thr residues mimicking the tan dem repeat portion of MUC2. (PTTTPLK) was investigated for the acceptor spe cificity to UDP-N-acetyl-D-galactosamine:peptide N-acetylgalactosaminyltran sferase isozymes, UDP-N-acetyl-D-galactosamine:peptide N-acetylgalactosamin yltransferase-T1, T2 and T3, The enzymatic reaction products were fractiona ted by the reversed-phase high performance liquid chromatograph?:, then cha racterized by matrix-assisted laser desorption ionization time of flight ma ss spectrometry and by a peptide sequencing analysis. A maximum of two, one or three N-acetyl-D-galactosamine residues was transferred by UDP-N-acetyl -D-galactosamine: peptide N-acetylgalactosaminyltransferase-T1, T2 or T3, r espectively. The preferential orders of N-acetyl-D-galactosamine incorporat ion were Thr-2, then Thr-4 for UDP-N-acetyl-D-galactosamine :peptide N-acet ylgalactosaminyltransferase-T1, Thr-2 for UDP-N-acetyl-D-galactosamine :pep tide N-acetylgalactosaminyltransferase-T2 and Thr-4, Thr-3, then Thr-2 for UDP-N-acetyl-D-galactosamine :peptide N-acetylgalactosaminyltransferase-T3. (C) 1999 Federation of European Biochemical Societies.