Phosphorylation of proteins and their functional and structural properties

Phosphoproteins are very important biologically and have the potential to improve the functional properties of proteins as food ingredients. Food proteins can be phosphorylated by protein kinases, which require an encoded specificity site on the protein or by use of POCl3, phosphorus pentoxide, other high energy phosphates or carbodiimides. In this paper we report the phosphorylation of alpha-lactalbumin, beta-lactoglobulin and zein by POCl3 and the effect on solubility, and functional and structural properties of the proteins. The paper also reviews published research (Chobert et al. J. Am. Oil Chem. Sec. 1987, 64, 1704-1711) in which tryptophan and lysine were covalently Linked to zein when they were added to the solution along with the protein and POCl3. The bound amino acids improved the nutritional value of zein from 4.5 to 48% relative to casein, when tested with Tetrahymena thermophili.