Asparagine-linked carbohydrate chains of inducible rat parotid proline-rich glycoprotein contain terminal beta-linked N-acetylgalactosamine.

Rats treated with daily injection of DL-isoproterenol for 10 consecutive days (25 mg kg(-1) body weight) showed marked induction of a proline-rich glycoprotein (GPRP) of 220 kDa. Proteinase K digestion of GPRP produced a homogeneous glycopeptide with an average chemical composition as follows (residues per mol): Pro4, Glx3, Asx2, Gly1, His1, Thr1, Arg1, GlcNAc5, GalNac1, Man3, Gal2-3, and Fuc1. The structural analysis of the asparagine-linked carbohydrate unit was performed by methylation, periodate oxidation and enzymatic degradation. Methylation studies indicated that the three mannosyl residues were substituted at 1,2-, 1,2,4-, and 1,3,6-positions. Fucose, N-acetylgalactosamine, 1.5 residues of galactose and 0.35 residues of N-acetylglucosamine were terminally located and one galactose residue was 1,4-substituted. Approximately four of the 5 N-acetylglucosamine residues were substituted at 1,4-position and approximately 1 residue of N-acetylglucosamine was substituted at 1,4,6-positions. Periodate oxidation studies and exoglycosidase results were consistent with the methylation data. Based on the results of Smith degradation, methylation and sequential exoglycosidase digestions a triantennary oligosaccharide structure having terminal N-acetylgalactosamine in one of the branches is proposed for the major Asn-linked carbohydrate moiety of GPRP.
AuthorsG S Bedi
JournalGlycoconjugate journal (Glycoconj J) Vol. 14 Issue 8 Pg. 907-16 (Dec 1997) ISSN: 0282-0080 [Print] ENGLAND
PMID9486423 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)
Chemical References
  • Carbohydrates
  • Oligosaccharides
  • Peptides
  • Asparagine
  • Isoproterenol
  • Animals
  • Asparagine (chemistry)
  • Carbohydrate Conformation
  • Carbohydrate Sequence
  • Carbohydrates (chemistry)
  • Gas Chromatography-Mass Spectrometry
  • Isoproterenol (pharmacology)
  • Molecular Sequence Data
  • Oligosaccharides (chemistry)
  • Parotid Gland (chemistry, drug effects, metabolism)
  • Peptide Biosynthesis (drug effects)
  • Peptides (chemistry)
  • Proline-Rich Protein Domains
  • Rats

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