Substrate recognition by UDP-N-acetyl-alpha-D-galactosamine: polypeptide n-acetyl-alpha-D-galactosaminyltransferase. Effects of chain length and disulphide bonding of synthetic peptide substrates.
A synthetic peptide AcTPPP, based on a threonine-containing sequence present in bovine myelin basic protein, is a potent acceptor of glycosyl transfer from UDP-N-acetylgalactosamine catalyzed by extracts of baby hamster kidney (BHK) cells or rabbit lymph node tissue. In contrast, the disulphide-linked peptide (AcTCPPP)2, based on a glycosylated sequence present in the hinge region of rabbit immunoglobulin G, is not an acceptor and inhibits glycosylation of AcTPPP. Extension of the cystine-containing peptide at the N-terminus produced weak acceptors but strong acceptors resulted when the cystine residue was reduced to form monomeric peptides. The acceptor specificity of the N-acetylgalactosaminyl-transferase activity of BHK cells is very similar to that of rabbit lymph node tissue. The results indicated that tissues actively secreting immunoglobulin do not contain a transferase activity adapted specifically for glycosylation of sequences containing cystine residues, and suggested that addition of an N-acetylgalactosamine to a threonine residue in the hinge region of rabbit immunoglobulin takes place during biosynthesis prior to the formation of the inter-chain disulphide bridge of fully assembled immunoglobulins.
Hughes
R C
RC
National Institute for Medical Research, The Ridgeway, Mill Hill, London NW71AA, United Kingdom.
Bradbury
A F
AF
Smyth
D G
DG
D000595:Amino Acid Sequence; D000828:Animal Population Groups; D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D003545:Cysteine / Q000378:metabolism; D005700:Galactosyltransferases / Q000378:metabolism*; D006031:Glycosylation; D007074:Immunoglobulin G / Q000378:metabolism; D007668:Kidney / Q000201:enzymology; D008198:Lymph Nodes / Q000201:enzymology; D008969:Molecular Sequence Data; D004676:Myelin Basic Protein / Q000378:metabolism; D017350:N-Acetylgalactosaminyltransferases; D009842:Oligopeptides / Q000378:metabolism; D011817:Rabbits; D013379:Substrate Specificity; D013912:Threonine / Q000378:metabolism; D000097763:Polypeptide N-acetylgalactosaminyltransferase
D003545:Cysteine; D005700:Galactosyltransferases; D007074:Immunoglobulin G; D004676:Myelin Basic Protein; D017350:N-Acetylgalactosaminyltransferases; D009842:Oligopeptides; D013912:Threonine; D000097763:Polypeptide N-acetylgalactosaminyltransferase