title: Characterization of N-acetyl-beta-D-galactosaminyltransferase from guinea-pig kidney involved in the biosynthesis of Sda antigen associated with Tamm-Horsfall glycoprotein.
abstract: This study reports the catalytic activity of N-acetyl-beta-D-galactosaminyltransferase from guinea-pig kidney towards such non-glycoprotein acceptors as small oligosaccharides and glycolipids, having a carbohydrate structure similar to that of the Sda antigen associated with human Tamm-Horsfall glycoprotein. 3'-O-Sialyllactose, but not 6'-O-sialyllactose or lactose, was an effective acceptor of the glycosyltransferase. On the basis of enzymic and chemical treatment of the tetrasaccharide obtained by the transfer of [14C]GalNAc to 3'-O-sialyllactose, we propose that the glycosyltransferase attaches beta-D-GalNAc to O-4 of the galactose residue that is substituted at O-3 by sialic acid. The GM3 ganglioside, in which the identical carbohydrate moiety of 3'-O-sialyllactose is bound to a ceramide residue, did not serve as an acceptor of the kidney-N-acetyl-beta-D-galactosaminyltransferase and did not behave as a competitive inhibitor of the Tamm-Horsfall glycoprotein in the transferase assay. These results indicate that the hydrophobic moiety in the ganglioside hinders the action of N-acetylgalactosaminyltransferase. Study of the transferase activity towards a heterogeneous glycopeptide species prepared from a Sd(a-) Tamm-Horsfall glycoprotein indicated that guinea-pig kidney enzyme preferentially transferred [14C]GalNAc to the oligosaccharides having a tetraantennary branching-structure.
mesh_terms: D000818:Animals; D001789:Blood Group Antigens; D001921:Brain / Q000201:enzymology; D002241:Carbohydrates / Q000032:analysis; D005700:Galactosyltransferases / Q000378:metabolism*; D006168:Guinea Pigs; D007668:Kidney / Q000201:enzymology*; D007700:Kinetics; D008861:Microsomes / Q000201:enzymology*; D009088:Mucoproteins / Q000096:biosynthesis*; D017350:N-Acetylgalactosaminyltransferases; D009844:Oligosaccharides / Q000302:isolation & purification; D013379:Substrate Specificity; D058949:Uromodulin
chemical_list: D001789:Blood Group Antigens; D002241:Carbohydrates; D009088:Mucoproteins; D009844:Oligosaccharides; C548612:UMOD protein, human; D058949:Uromodulin; D005700:Galactosyltransferases; D017350:N-Acetylgalactosaminyltransferases; C003742:UDPgalactosamine-galactose acetylgalactosaminyltransferase