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Effect of calcium on the stability of mares' milk lysozyme

Published online by Cambridge University Press:  01 June 2009

Richard L. J. Lyster
Affiliation:
Department of Food Science and Technology, Whiteknights, PO Box 226, University of Reading, Reading RG2 9AP, UK

Summary

The three aspartic acid residues that form part of the Ca-binding site of mares' milk lysozyme have apparent pK values of 4·9, 4·3 and 4·1. The fluorescence of tryptophan has been used to compare the denaturation of mares' milk lysozyme by guanidinium chloride at various concentrations of Ca with that of hens' egg-white lysozyme (EC 3.2.1.17) and α-lactalbumin. Fluorescence revealed an intermediate stage in the denaturation of mares' milk lysozyme. The Ca-free form of mares' milk lysozyme is slightly more stable than that of α-lactalbumin, but its interaction with Ca is similar to that of α-lactalbumin, since only the native state binds Ca. Three-state models of denaturation can usefully be displayed on a ternary diagram.

Type
Original Articles
Copyright
Copyright © Proprietors of Journal of Dairy Research 1992

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