The carbohydrate linkage site of cow colostrum trypsin inhibitor.
Cow colostrum trypsin inhibitor (chromatographic form AIV[7])was subjected to basic conditions that favour beta-elimination of carbohydrates from O-glycosidic linkages. The unchanged carbohydrate composition and the unchanged values for serine and threonine indicate the presence of an alkali-stable N-glycosidic bond to asparagine. From a tryptic digest of S-aminoethylated inhibitor the glyco-decapeptide (residues 24 through 33) was isolated. The carbohydrate composition was identical with that of the S-aminoethylated inhibitor. Further degradation of this peptide by carboxypeptidase C (and aminopeptidase) produced the glycopeptide Asn(CHO)-Ser-(Thr) with the same carbohydrate composition. Thus, a single carbohydrate moiety is bound by a N-glycosidic linkage to asparagine-27 of the colostrum inhibitor. It is located opposite to the reactive site at the base of a pear-shaped molecule.
D000818:Animals; D001665:Binding Sites; D002241:Carbohydrates / Q000235:genetics*; D002268:Carboxypeptidases / Q000235:genetics; D002417:Cattle; D003126:Colostrum / Q000201:enzymology*; D008040:Genetic Linkage; D014361:Trypsin Inhibitors / Q000235:genetics*
D002241:Carbohydrates; D014361:Trypsin Inhibitors; D002268:Carboxypeptidases