RESUMO
New neutral oligosaccharides from cow colostrum kappa-casein were identified and characterized by 500-MHz 1H-NMR spectroscopy. Their structures are Gal beta(1----3)GalNAc-ol, Gal beta(1----3)[GlcNAc beta(1----6)]GalNAc-ol, Gal beta(1----3)[Gal beta(1----4)GlcNAc beta(1----6)]GalNAc-ol, Gal beta(1----3)[Fuc alpha(1----3)[Gal beta(1----4)]GlcNAc beta(1----6)]GalNAc-ol. The tetrasaccharide and the cow colostrum kappa-caseinoglycopeptide which contains this oligosaccharide inhibit the hemagglutination of blood group I human erythrocytes. In cow mature milk only the disaccharide is characterized. The variability of these neutral oligosaccharides in cow kappa-casein as a function of time after calving is studied.
Assuntos
Antígenos de Grupos Sanguíneos , Carboidratos/análise , Caseínas/análise , Colostro/análise , Glicopeptídeos/análise , Sistema do Grupo Sanguíneo I , Trabalho de Parto , Oligossacarídeos/análise , Animais , Configuração de Carboidratos , Sequência de Carboidratos , Caseínas/imunologia , Bovinos , Cromatografia Líquida de Alta Pressão , Eritrócitos/imunologia , Feminino , Glicopeptídeos/imunologia , Humanos , Isoanticorpos/análise , Dados de Sequência Molecular , Gravidez , Álcoois Açúcares/análise , Fatores de TempoRESUMO
The study of glycopeptides obtained after enzymic digestions of bovine colostrum kappa-caseinoglycopeptide obtained 15 minutes after calving, demonstrated the presence of two prosthetic sugar groups linked to threonine residues, instead of only one and up to 10 in the case of bovine (normal) and human caseinoglycopeptides, respectively. The secondary structure of bovine kappa-caseinoglycopeptide was reinvestigated.
Assuntos
Caseínas , Colostro/análise , Acetilgalactosamina/análise , Acetilglucosamina/análise , Sequência de Aminoácidos , Aminoácidos/análise , Animais , Bovinos , Feminino , Glicopeptídeos/análise , GravidezRESUMO
Cow kappa-casein contains only three different sugars (Gal, GalNAc, NeuNAc). However detailed analyses achieved mainly by gas liquid chromatography suggested a microheterogeneity at the sugar level. After alkaline borohydride treatment, filtration on Bio-Gel P4 and paper chromatography, different carbohydrate parts were obtained. The two main compounds had the following molar compositions: GalNAc (1), Gal(1) and NeuNAc (1) and GalNAc (1), Gal(1) and NeuNAc (2). From these data and our previous sequence studies, some formulae of the polysaccharide part were proposed. One of them was closely related to the sugar sequence of a glycopeptide with MN activity which was in agreement with our observation concerning a cross antigenic reactivity between the N blood group substances and the caseinoglycopeptides. All the polysaccharide parts isolated from colostrum caseinoglycopeptide were much more complex than those obtained from the normal glycopeptide, confirming an evolution of the sugar part as a function of time after parturition.