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J Dairy Res. 2001 May;68(2):197-208.

Heterogeneity of caprine kappa-casein macropeptide.

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Instituto de Fermentaciones Industriales (CSIC), Madrid, Spain.


The heterogeneity of caprine caseinmacropeptide (CMP) was determined by means of treatments with neuraminidase and acid phosphatase and analyses by anion exchange FPLC and reversed-phase (RP)-HPLC, with on-line and off-line electrospray ionization mass spectrometry. The main CMP components were two non-glycosylated and di-phosphorylated forms, as well as two other mono-phosphorylated species, each corresponding to a genetic variant of caprine kappa-casein due to the silent substitution Ile/Val at position 119. Asialo-aglyco mono- and di-phosphorylated forms were found in the ratios 8-14% and 86-92%, respectively. Approximately 36% of caprine CMP was glycosylated. Based on the obtained molecular masses, the occurrence of tri-, di- and monosaccharide-containing di-phosphorylated CMP are reported, assuming that N-acetylgalactosamine, galactose, N-acetyl and N-glycolylneuraminic acids would constitute the main monosaccharides of caprine CMP. CMP microheterogeneity due to the genetic polymorphism was also observed in the glycosylated forms.

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