N-acetylgalactosamine (GalNAc) transfer to the common carbohydrate-protein linkage region of sulfated glycosaminoglycans. Identification of UDP-GalNAc:chondro-oligosaccharide alpha-N-acetylgalactosaminyltransferase in fetal bovine serum.
During the course of a study of elucidate the role of modification of the common polysaccharide-protein linkage structure, GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl beta 1-O-Ser, in biosynthetic sorting mechanisms of the different sulfated glycosaminoglycan chains, a novel N-acetylgalactosamine (GalNAc) transferase was discovered in fetal bovine serum. The enzyme catalyzed the transfer of [3H]GalNAc from UDP-[3H]GalNAc to linkage tetrasaccharide and hexasaccharide serines synthesized chemically and to various regular oligosaccharides containing terminal D-glucuronic acid (GlcA), which were prepared from chondroitin and chondroitin sulfate using testicular hyaluronidase digestion. The labeled products obtained with the linkage tetra- and hexasaccharide serines and with the tetrasaccharide (GlcA beta 1-3GalNAc)2 were resistant to digestion with chondroitinase AC-II and beta-N-acetylhexosaminidase but sensitive to alpha-N-acetylgalactosaminidase digestion, indicating that the enzyme is an alpha-N-acetylgalactosaminyltransferase. This finding is in contrast to that of Rohrmann et al. (Rohrmann, K., Niemann, R., and Buddecke, E. (1985) Eur. J. Biochem., 148, 463-469), who reported that a corresponding product was susceptible to digestion with beta-N-acetylhexosaminidase. The presence of a sulfate group at C4 of the penultimate GalNAc or Gal units markedly inhibited the transfer of GalNAc to the terminal GlcA, while a sulfate group at C6 of the GalNAc had little effect on the transfer. Moreover, a slight but significant transfer of [3H]GalNAc was observed to an oligosaccharide containing terminal 2-O-sulfated GlcA as acceptor, whereas no incorporation was detected into oligosaccharides containing terminal unsaturated or 3-O-sulfated GlcA units. These results suggest that this novel serum enzyme is a UDP-GalNAc:chondro-oligosaccharide alpha 1-3- or 1-4-N-acetylgalactosaminyltransferase. The possibility of involvement of this enzyme in glycosaminoglycan biosynthesis is discussed.
Kitagawa
H
H
Department of Biochemistry, Kobe Pharmaceutical University, Japan.
Tanaka
Y
Y
Tsuchida
K
K
Goto
F
F
Ogawa
T
T
Lidholt
K
K
Lindahl
U
U
Sugahara
K
K
D000116:Acetylgalactosamine / Q000378:metabolism*; D000818:Animals; D002240:Carbohydrate Sequence; D002417:Cattle; D006025:Glycosaminoglycans / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D017350:N-Acetylgalactosaminyltransferases / Q000097:blood*; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism; D013237:Stereoisomerism; D013379:Substrate Specificity; D013431:Sulfates; D014536:Uridine Diphosphate N-Acetylgalactosamine / Q000378:metabolism
D006025:Glycosaminoglycans; D009844:Oligosaccharides; D013431:Sulfates; D014536:Uridine Diphosphate N-Acetylgalactosamine; D017350:N-Acetylgalactosaminyltransferases; D000116:Acetylgalactosamine