Two N-acetylgalactosaminyltransferase are involved in the biosynthesis of chondroitin sulfate

Eur J Biochem. 1985 May 2;148(3):463-9. doi: 10.1111/j.1432-1033.1985.tb08862.x.


Two N-acetylgalactosaminyltransferases, designated I and II, have been purified from the microsomal fraction of calf arterial tissue and separated on Bio-Gel A. N-Acetylgalactosaminyltransferase I was purified 450-fold. It requires Mn2+ for maximal activity and transfers N-acetylgalactosamine residues from UDP-[1-3H]GalNAc in beta-glycosidic configuration to the non-reducing terminus of the acceptor substrates GlcA(beta 1-3)Gal(beta 1-3)Gal, GlcA(beta 1-3)Gal(beta 1-4)Glc and GlcA(beta 1-3)Gal. Even-numbered chondroitin oligosaccharides serve as acceptors for N-acetylgalactosaminyltransferase II, which transfers N-acetylgalactosamine from UDP-[1-3H]GalNAc to the non-reducing glucuronic acid residues of oligosaccharide acceptor substrates. Maximum transfer rates were obtained with a decasaccharide derived from chondroitin. Longer or shorter-chain chondroitin oligosaccharides are less effective acceptor substrates. All reaction products formed by N-acetylgalactosaminyltransferases I and II are substrates of beta-N-acetylhexosaminidase, which splits off the transferred [1-3H]GalNAc completely. In the microsomal fraction N-acetylgalactosaminyltransferase II had a 300-fold higher specific activity than N-acetylgalactosaminyltransferase I. In contrast to enzyme I, enzyme II loses much of its activity during the purification procedure and undergoes rapid thermodenaturation. GlcA-Gal-Gal is a characteristic sequence of the carbohydrate-protein linkage region of proteochondrioitin sulfate. The acceptor capacity of this trisaccharide suggests that N-acetylgalactosaminyltransferase I is involved in the synthesis of the carbohydrate-protein linkage region. Since N-acetylgalactosaminyltransferase II is highly specific for chondroitin oligosaccharides, we conclude that it participates in chain elongation during chondroitin sulfate synthesis.

MeSH terms

  • Animals
  • Aorta / enzymology
  • Aorta / metabolism
  • Catalysis
  • Cattle
  • Chemical Phenomena
  • Chemistry
  • Chondroitin / analogs & derivatives*
  • Chondroitin Sulfates / biosynthesis*
  • Chromatography, Gel
  • Drug Stability
  • Galactosyltransferases / metabolism*
  • Hot Temperature
  • Microsomes / enzymology
  • N-Acetylgalactosaminyltransferases*
  • Peptide Chain Elongation, Translational
  • Solubility
  • Substrate Specificity


  • Chondroitin
  • Chondroitin Sulfates
  • Galactosyltransferases
  • N-Acetylgalactosaminyltransferases
  • UDPgalactosamine-galactose acetylgalactosaminyltransferase