title: A novel human beta1,3-N-acetylgalactosaminyltransferase that synthesizes a unique carbohydrate structure, GalNAcbeta1-3GlcNAc.
abstract: We found, using a BLAST search, a novel human gene (GenBank trade mark accession number BC029564) that possesses beta3-glycosyltransferase motifs. The full-length open reading frame consists of 500 amino acids and encodes a typical type II membrane protein. This enzyme has a domain containing beta1,3-glycosyltransferase motifs, which are widely conserved in the beta1,3-galactosyltransferase and beta1,3-N-acetylglucosaminyltransferase families. The putative catalytic domain was expressed in human embryonic kidney 293T cells as a soluble protein. Its N-acetylgalactosaminyltransferase activity was observed when N-acetylglucosamine (GlcNAc) beta1-O-benzyl was used as an acceptor substrate. The enzyme product was determined to have a beta1,3-linkage by NMR spectroscopic analysis, and was therefore named beta1,3-N-acetylgalactosaminyltransferase-II (beta3GalNAc-T2). The acceptor substrate specificity of beta3GalNAc-T2 was examined using various oligosaccharide substrates. Galbeta1-3(GlcNAcbeta1-6)GalNAcalpha1-O-para-nitrophenyl (core 2-pNP) was the best acceptor substrate for beta3GalNAc-T2, followed by GlcNAcbeta1-4GlcNAcbeta1-O-benzyl, and GlcNAcbeta1-6GalNAcalpha1-O-para-nitrophenyl (core 6-pNP), among the tested oligosaccharide substrates. Quantitative real time PCR analysis revealed that the beta3Gal-NAc-T2 transcripts was restricted in its distribution mainly to the testis, adipose tissue, skeletal muscle, and ovary. Its putative orthologous gene, mbeta3GalNAc-T2, was also found in a data base of mouse expressed sequence tags. In situ hybridization analysis with mouse testis showed that the transcripts are expressed in germ line cells. beta3GalNAc-T2 efficiently transferred GalNAc to N-glycans of fetal calf fetuin, which was treated with neuraminidase and beta-galactosidase. However, it showed no activity toward any glycolipid examined. Although the GalNAcbeta1-3GlcNAcbeta1-R structure has not been reported in humans or other mammals, we have discovered a novel human glycosyltransferase producing this structure on N- and O-glycans.
authors.affiliation: Research Center for Glycoscience (RCG), National Institute of Advanced Industrial Science and Technology (AIST), Open Space Laboratory Central-2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Hiruma
authors.forename: Akira
authors.initials: A
authors.lastname: Togayachi
authors.forename: Kayo
authors.initials: K
authors.lastname: Okamura
authors.forename: Takashi
authors.initials: T
authors.lastname: Sato
authors.forename: Norihiro
authors.initials: N
authors.lastname: Kikuchi
authors.forename: Yeon-Dae
authors.initials: YD
authors.lastname: Kwon
authors.forename: Aya
authors.initials: A
authors.lastname: Nakamura
authors.forename: Katsuya
authors.initials: K
authors.lastname: Fujimura
authors.forename: Masanori
authors.initials: M
authors.lastname: Gotoh
authors.forename: Kouichi
authors.initials: K
authors.lastname: Tachibana
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Ishizuka
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Noce
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakanishi
authors.forename: Hisashi
authors.initials: H
authors.lastname: Narimatsu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002240:Carbohydrate Sequence; D019295:Computational Biology; D006801:Humans; D017403:In Situ Hybridization; D051379:Mice; D008969:Molecular Sequence Data; D017350:N-Acetylgalactosaminyltransferases / Q000235:genetics* / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism*; D010802:Phylogeny; D011522:Protons; D012333:RNA, Messenger / Q000032:analysis; D013379:Substrate Specificity
chemical_list: D009844:Oligosaccharides; D011522:Protons; D012333:RNA, Messenger; C000594712:B3GALNT2 protein, human; D017350:N-Acetylgalactosaminyltransferases