Cross-linkgae between casein and colloidal calcium phosphate in bovine casein micelles
1991
Aoki, T.
The existence of cross-linkage between casein and colloidal calcium phosphate (CCP) has been proved by separating casein aggregates cross-linked by CCP from bovine casein micelles. Not only calcium and phosphate but also citrate play an important role in cross-linking of casein by CCP. The incorporation rates of individual casein constituents into casein aggregates cross-linked by CCP were in the order alpha(S2)- > alpha(S1)- > beta-casein. This order was the reverse of the order of the dissociation rates of casein aggregates cross-linked by CCP during dialysis. The higher the ester phosphate content, the faster was the incorporation rate of the individual casein constituent and the slower is the dissociation rate. Ester phosphate groups were identified as the sites for interaction with CCP since alpha(S1)-, alpha(S2)- and beta-casein were cross-linked by CCP while kappa- and gamma-casein and dephosphorylated alpha(S1)-casein were not cross-linked. Relation between CCP cross-linkage and changes in casein micelles on heating and cooling was also described.
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