A novel member of the human ppGalNAc-T family ppGalNAc-T20 was identified and characterized Amino acid alignment revealed a high sequence identity between ppGalNAc-T20 and -T10 In the GalNAc transfer assay towards mucin-derived peptide substrates the recombinant ppGalNAc-T20 demonstrated to be a typical glycopeptide GaINAc-transferase that exhibits activity towards mono-GalNAc-glycosylated peptide EA2 derived from rat submandibular gland mum but no activity towards non-modified EA2 The in vitro catalytic property of ppGalNAc-T20 was compared with that of ppGalNAc-T10 to show different acceptor substrate specificities and kinetic constants The ppGalNAc-T20 transcript was found exclusively in testis and brain In situ hybridization further reveals that ppGalNAc-T20 was specifically localized in primary and secondary spermatocytes of the two meiotic periods suggesting that it may involve in O-glycosylation during mouse spermatogenesis (C) 2010 Elsevier Inc All rights reserved