Hostname: page-component-745bb68f8f-grxwn Total loading time: 0 Render date: 2025-01-12T04:27:27.912Z Has data issue: false hasContentIssue false
  • English
  • Français

Influence of aggregation on the susceptibility of casein to proteolysis

Published online by Cambridge University Press:  01 June 2009

P. F. Fox
P. F. Fox
Affiliation:
National Dairy Research Centre, The Agricultural Institute, Fermoy, Co. Cork, Irish Republic
Get access Rights & Permissions [Opens in a new window]

Summary

The susceptibility of the casein in milk to proteolysis was shown to be greatly influenced by its state of aggregation. In normal milk, where the casein is largely in micellar form, the αs1- and β-caseins are almost inaccessible to proteolysis. On removal of the colloidal phosphate, the casein micelles disintegrate, rendering the components, especially the αs1-casein, accessible to proteolysis. The role of colloidal calcium phosphate in the casein micelle is believed to be that of a non-specific aggregating agent which can be effectively replaced by calcium. Dissolved colloidal phosphate can be effectively reformed by elevation of the pH of colloidal phosphate-free (CPF) milk before equilibrium dialysis. Addition of κ-casein to CPF milk also causes aggregation of the component caseins but the micelles formed are smaller than those of normal milk.

The behaviour of micellar β-casein differs considerably from that of micellar αs1-casein. The evidence suggests that part of the β-casein freely dissociates either outside or within the micelle when the temperature is reduced. The temperature dependence of the susceptibility of β-casein to proteolysis was similar in skim-milk and in solutions of sodium caseinate, and increased as the temperature was reduced. αs1-Casein was quite resistant to proteolysis in normal milk but became susceptible when the micelle structure was disrupted on removal of colloidal phosphate.

It is concluded that limited proteolysis may prove a valuable technique in the study of casein micelle structure.

Type
Original Articles
Information
Journal of Dairy Research , Volume 37 , Issue 2 , June 1970 , pp. 173 - 180
Copyright
Copyright © Proprietors of Journal of Dairy Research 1970

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Bang-Jensen, V., Foltmann, B. & Rombauts, W. (1964). C. r. Trav. Lab. Carlsberg 34, 326.Google Scholar
Berridge, N. J. (1945). Biochem. J. 39, 179.CrossRefGoogle Scholar
Cerbulis, J., Custer, J. H. & Zittle, C. A. (1958). Archs Biochem. Biophys. 84, 417.CrossRefGoogle Scholar
Cerbulis, J., Custer, J. H. & Zittle, C. A. (1960). J. Dairy Sci. 43, 1725.CrossRefGoogle Scholar
Downey, W. K., Murphy, R. F. & Aherne, S. A. (1969). Biochem. J. 115, 21 P.CrossRefGoogle Scholar
Fish, J. C. (1957). Nature, Lond. 180, 345.CrossRefGoogle Scholar
Fox, P. F. (1969). J. Dairy Sci. 52, 1214.CrossRefGoogle Scholar
Garnier, J. (1966). J. molec. Biol. 19, 586.Google Scholar
Ledford, R. A., Chen, J. H. & Nath, K. R. (1968). J. Dairy Sci. 51, 792.CrossRefGoogle Scholar
Ledford, R. A., O'Sullivan, A. C. & Nath, K. R. (1966). J. Dairy Sci. 49, 1098.CrossRefGoogle Scholar
Lindqvist, B. & Storgårds, T. (1959 a). 15th Int. Dairy Congr., London 3, 679.Google Scholar
Lindqvist, B. & Storgårds, T. (1959 b). Acta chem. scand. 13, 1839.CrossRefGoogle Scholar
Lindqvist, B. & Storgårds, T. (1960). Acta chem. scand. 14, 575.Google Scholar
Lindqvist, B. & Storårds, T. (1962). 16th Int. Dairy Congr., Copenhagen, B 665.Google Scholar
Mabbitt, L. A., Chapman, H. R. & Berridge, N. J. (1955). J. Dairy Res. 22, 365.Google Scholar
McGann, T. C. A. & Pyne, G. T. (1960). J. Dairy Res. 27, 403.CrossRefGoogle Scholar
Morr, C. V. (1967). J. Dairy Sci. 50, 1744.CrossRefGoogle Scholar
Payens, T. A. J. (1966). J. Dairy Sci. 49, 1317.CrossRefGoogle Scholar
Payens, T. A. J. & van Markwijk, B. W. (1963). Biochim. biophys. Acta 71, 517.CrossRefGoogle Scholar
Pyne, G. T. & McGann, T. C. A. (1960). J. Dairy Res. 27, 9.CrossRefGoogle Scholar
Rose, D. (1965). J. Dairy Sci. 48, 139.CrossRefGoogle Scholar
Rose, D. (1968). J. Dairy Sci. 51, 1897.CrossRefGoogle Scholar
Rose, D. (1969). Dairy Sci. Abstr. 31, 171.Google Scholar
Rose, D. & Colvin, J. R. (1966 a). J. Dairy Sci. 49, 351.CrossRefGoogle Scholar
Rose, D. & Colvin, J. R. (1966 b). J. Dairy Sci. 49, 1091.CrossRefGoogle Scholar
ter Horst, M. G. (1963). Ned. Melk- en Zuiveltijdschr. 17, 185.Google Scholar
Thompson, M. P., Kiddy, C. A., Johnston, J. O. & Weinberg, R. M. (1964). J. Dairy Sci. 47, 378.CrossRefGoogle Scholar
Warren, L. (1959). J. biol. Chem. 234, 1971.CrossRefGoogle Scholar
Waugh, D. F. (1958). Discuss. Faraday Soc. 25, 186.CrossRefGoogle Scholar
Waugh, D. F. & Noble, R. W. Jr (1965). J. Am. chem. Soc. 87, 2246.CrossRefGoogle Scholar
Zittle, C. A. & Custer, J. H. (1963). J. Dairy Sci. 46, 1183.CrossRefGoogle Scholar