Structure of the Asialyl Oligosaccharide Chains of kappa-Casein Isolated from Ovine Colostrum

Abstract

Three oligosaccharide alditols, a di (44–63%), tetra (32–46%), and a pentasacchariditol (5–10%) have been isolated from desialylated caseinomacropeptide obtained from ϰ‐casein of ewe colostrum. The disacchariditol is 2‐acetam‐do‐2‐deoxy‐3‐O‐(β‐D‐galactopyranosyl)galactitol; in the tetrasaccharide this unit is substituted in position 6 of the galactosaminitol moiety by 2‐acetamido‐2‐deoxy‐4‐O‐(β‐D‐galactopyranosyl)‐β‐D‐glucopyranose, while the pentasacchariditol is derived from the tetrasaccharide by addition of a D‐galactopyranosyl unit to position 3 of the galactopyranose unit substituting the glucosamine unit.

Physiology and Biochemistry of Lactation

“…The K-casein of bovine colostrum carries more carbohydrate, in chains of greater complexity. The oligosaccharide chains of K-casein from ovine colostrum also have the Gal-j3(1~3)-Gal-NAc structure above, but carry Gal-j3(1~4)-Glc-NAc-j3(1~6) and Gal-j3(1 ~3)-Gal-j3(1 ~4)-Glc-NAc-j3(1 ~6) attached to some of the Gal-NAc residues (Soulier et al, 1980). The exact structure is not critical, but the presence of NAc-Neu residues (sialic acid residues) is.…”

Casein phosphoproteome: Identification of phosphoproteins by combined mass spectrometry and two‐dimensional gel electrophoresis

“…Ovine k-casein is O-glycosylated and six Thr residues have been proposed as putative glycosylation sites [22,23]. Ovine k-CN contains both N-acetyl and N-glycolyl-neuraminic acids at all stages of lactation [24][25][26]. The disaccharide, Among the mass signals relating to k-CN tryptic peptides, only those referring to the glycosylated and phosphorylated peptides k-CN (113-171), 113-143, and 144-171 have been reported in Table 4.…”

Characterization of the Glycans of Equine κ-Casein

“…In mature cow milk glycans corresponding to the analyzed structures I, III, IV, VI, and VII were identified by several authors, with the tetrasaccharide I as the main glycan. − Additionally, previous studies were able to confirm these results in the analysis of the glycans of bovine κ-casein or bovine GMP after derivatization with PMP. , The glycan spectrum of κ-casein in bovine colostrum is significantly more complex due to the additional presence of GlcNAc and fucose (Fuc). , The κ-casein of bovine colostrum also contains glycan structures that are comparable to the neutral tetrasaccharide V and acidic pentasaccharide II found in the present study in equine κ-casein. ,, The glycan spectrum in mature goat and sheep milk is very similar to that of mature cow milk, except that Neu5Ac may be partially or completely replaced by N -glycolylneuraminic acid (Neu5Gc) in the individual structures. − As for bovine colostrum, glycans containing GlcNAc in the form of a core-2 structure were identified for κ-casein in ovine colostrum . In addition to commercially relevant ruminants, the glycans of human κ-casein have also been studied in the past.…”