Modeling of calcium-induced solubility profiles of casein for biotechnology: Influence of primary structure and posttranslational modification

Publisher Website
Google Scholar
Abstract
Molecular biology holds the promise of new tools for the food industry which include proteins with tailor-made functionality. Without a fundamental knowledge of the molecular bases of these properties, implementation will be strictly empirical. For example, the phenomena of salt-induced precipitation of proteins (salting-out) and their resolubilization (salting-in) has heretofore been discussed only qualitatively. A quantitative method, using Wyman's theory of thermodynamic linkage, has been developed and tested on the calcium-induced solubility profiles of the major milk proteins, the caseins. Salting-out was described by a salt-binding constant,k1, andn, the number of moles of salt bound; salting-in was described by the corresponding termsk2 andm. The magnitude of these parameters indicated involvement of protein phosphate groups in binding and precipitation, but enzymatic dephosphorylation showed significant increases ink1 andk2 indicating involvement of carboxylate groups as well. Studies on two genetic variants of αs1-casein indicated the importance of a hydrophobically stabilized intramolecular ion pair in the functionality of the protein. These studies have led to a fuller understanding of the molecular basis for the solubility behavior of caseins and have laid the groundwork for future computer simulation of food protein functionality.