Modification of galactose and N-acetylgalactosamine residues by oxidation of C-6 hydroxyls to the aldehydes followed by reductive amination: model systems and antifreeze glycoproteins.
Amino acids and peptides have been attached to the C-6 hydroxyls of the galactose and the N-acetylgalactosamine by first oxidizing the C-6 hydroxyls to the aldehydes by galactose oxidase in the presence of small amounts of catalase, followed by reductive amination (alpha-amino group) in the presence of cyanoborohydride. The activity of oxidized antifreeze glycoprotein was greater than 70% of the original, and considerable activity has been retained with some substitutions on reductive amination using cyanoborohydride. The following were some activities retained (as compared with the oxidized antifreeze glycoprotein): Gly, 64; (Gly)2, 88; (Gly)3, 82; (Gly)4, 70; Gly-Gly-NH2, 44; Gly-Glu, 13; Gly-Leu, 40; Gly-Tyr, 57; Gly-Gly-Leu, 50; Gly-Gly-Phe, 30; and Gly-Gly-Val, 35. On amino acid analysis of acid hydrolysates, some release of the amino acid attached by amination occurred; e.g., Gly-Tyr gave 0.26 Gly and 0.49 Tyr per disaccharide.
Osuga
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Department of Food Science and Technology, University of California, Davis 95616.
Feather
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Shah
M J
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Feeney
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D000116:Acetylgalactosamine / Q000031:analogs & derivatives*; D000586:Amination; D021301:Antifreeze Proteins; D055598:Chemical Phenomena; D002621:Chemistry; D005688:Galactosamine; D005690:Galactose / Q000031:analogs & derivatives*; D005692:Galactose Oxidase; D006023:Glycoproteins; D008956:Models, Chemical; D010084:Oxidation-Reduction
D021301:Antifreeze Proteins; D006023:Glycoproteins; D005688:Galactosamine; D005692:Galactose Oxidase; D000116:Acetylgalactosamine; D005690:Galactose