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Separation of casein aggregates cross-linked by colloidal calcium phosphate from bovine casein micelles by high performance gel chromatography in the presence of urea

Published online by Cambridge University Press:  01 June 2009

Takayoshi Aoki
Affiliation:
Department of Animal Science, Faculty of Agriculture, Kagoshima University, Kagoshima 890, Japan
Yoshitaka Kako
Affiliation:
Department of Animal Science, Faculty of Agriculture, Kagoshima University, Kagoshima 890, Japan
Tsuneaki Imamura
Affiliation:
Department of Applied Biochemistry, Faculty of Applied Biological Science, Hiroshima University, Fukuyama 720, Japan

Summary

High performance gel chromatography of the casein micelles disaggregated by 6 m-urea was carried out on a TSK-GEL G4000SW column using 6 M-urea synthetic milk serum as the effluent. The eluate was divided into two fractions. Fast eluted fraction 1 decreased from 67·5 to 57·3% on reduction of casein micelles and was not observed in reduced colloidal phosphate-free casein micelles. Fraction 1 from reduced casein micelles contained 1·7 times as much Ca and Pi bound to casein as did whole casein micelles, while fraction 2 essentially contained only bound Ca. These facts indicated that fraction 1 of reduced casein micelles consisted of the casein aggregates cross-linked by colloidal Ca phosphate (CCP). Polyacrylamide-gel electrophoresis showed that fraction 1 of reduced casein micelles contained more αs1- and αs2-caseins and less β-casein than whole micellar casein. No κ-casein was detected in fraction 1 of reduced casein micelles. It is suggested that the ester phosphate groups of casein are the sites for interaction with CCP.

Type
Original Articles
Copyright
Copyright © Proprietors of Journal of Dairy Research 1986

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References

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