title: A new beta-1,2-N-acetylglucosaminyltransferase that may play a role in the biosynthesis of mammalian O-mannosyl glycans.
abstract: Recent studies have shown that O-mannosyl glycans are present in several mammalian glycoproteins. Although knowledge on the functional roles of these glycans is accumulating, their biosynthetic pathways are poorly understood. Here we report the identification and initial characterization of a novel enzyme capable of forming GlcNAc beta 1-2Man linkage, namely UDP-N-acetylglucosamine: O-linked mannose beta-1,2-N-acetylglucosaminyltransferase in the microsome fraction of newborn rat brains. The enzyme transfers GlcNAc to beta-linked mannose residues, and the formed linkage was confirmed to be beta 1-2 on the basis of diplococcal beta-N-acetylhexosaminidase susceptibility and by high-pH anion-exchange chromatography. Its activity is linearly dependent on time, protein concentration, and substrate concentration and is enhanced in the presence of manganese ion. Its activity is not due to UDP-N-acetylglucosamine: alpha-3-D-mannoside beta-1,2-N-acetylglucosaminyltransferase I (GnT-I) or UDP-N-acetylglucosamine: alpha-6-D-mannoside beta-1,2-D-acetylglucosaminyltransferase II (GnT-II), which acts on the early steps of N-glycan biosynthesis, because GnT-I or GnT-II expressed in yeast cells did not show any GlcNAc transfer activity against a synthetic mannosyl peptide. Taken together, the results suggest that the GlcNAc transferase activity described here is relevant to the O-mannosyl glycan pathway in mammals.
authors.affiliation: Department of Glycobiology, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakaecho, Itabashi-ku, Tokyo 173-0015, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Takahashi
authors.forename: T
authors.initials: T
authors.lastname: Sasaki
authors.forename: H
authors.initials: H
authors.lastname: Manya
authors.forename: Y
authors.initials: Y
authors.lastname: Chiba
authors.forename: A
authors.initials: A
authors.lastname: Yoshida
authors.forename: M
authors.initials: M
authors.lastname: Mizuno
authors.forename: H
authors.initials: H
authors.lastname: Ishida
authors.forename: F
authors.initials: F
authors.lastname: Ito
authors.forename: T
authors.initials: T
authors.lastname: Inazu
authors.forename: N
authors.initials: N
authors.lastname: Kotani
authors.forename: S
authors.initials: S
authors.lastname: Takasaki
authors.forename: M
authors.initials: M
authors.lastname: Takeuchi
authors.forename: T
authors.initials: T
authors.lastname: Endo
mesh_terms: D000818:Animals; D008358:Mannose / Q000737:chemistry*; D017351:N-Acetylglucosaminyltransferases / Q000737:chemistry / Q000378:metabolism*; D011134:Polysaccharides / Q000096:biosynthesis* / Q000737:chemistry; D051381:Rats; D011916:Rats, Inbred F344; D014407:Tumor Cells, Cultured
chemical_list: D011134:Polysaccharides; D017351:N-Acetylglucosaminyltransferases; C037649:N-acetyllactosaminide beta-1,6-N-acetylglucosaminyltransferase; D008358:Mannose