Evidence from in vitro glycosylation with polypeptide N acetylgalactosaminyltransferases GalNAc T 1 and GalNAc T 2 in concert with mass spectrometric analyses of in vivo glycosylated MUC 1 probes from transiently transfected HEK 293 cells indicated reduced glycosylation densities of repeats with three concerted replacements : AHGVTSAPESRPAPGSTAPA . ^^^