The effects of limited proteolysis by trypsin on human haptoglobin.
Trypsin digestion of haptoglobin resulted i four glycopeptides. The glycopeptides were characterized by amino acid composition and molecular weight, as determined by thin-layer chromatography, and sodium dodecyl sulphate-polyacrylamide gel electrophoresis in the presence or absence of 2-mercaptoethanol. Hemoglobin-binding capacity and immunological properties were investigated. glycopeptides I and II did not form an active complex with hemoglobin and they inhibited the reaction of haptoglobin with specific antiserum by over 70%. Glycopeptides III and IV showed 11 and 4% of the hemoglobin-binding capacity and 82 and 67% of antigenic reactivity of native haptoglobin, respectively. Glycopeptide IV contained three antigenic determinants, whereas glycopeptides III contained four, one of them being exposed by trypsin digestion. In crossed two-dimensional immunoelectrophoresis, glycopeptide III showed at least four components reacting with antihaptoglobin serum, and glycopeptide IV, two components.
D000596:Amino Acids / Q000032:analysis; D000939:Epitopes / Q000032:analysis; D006020:Glycopeptides / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D006242:Haptoglobins / Q000032:analysis* / Q000276:immunology; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D005779:Immunodiffusion; D008970:Molecular Weight; D014357:Trypsin
D000596:Amino Acids; D000939:Epitopes; D006020:Glycopeptides; D006242:Haptoglobins; D006454:Hemoglobins; D014357:Trypsin