Dual effects of sodium phytate on the structural stability and solubility of proteins

The interaction between sodium phytate and three proteins was studied using solubility experiments and differential scanning calorimetry (DSC) to assess structural stability. Lysozyme, which is positively charged at neutral pH, bound phytate by an electrostatic interaction. There was evidence that phytate cross-linked lysozyme molecules forcing them out of solution. Myoglobin and human serum albumin, which were neutral or negatively charged, respectively, displayed association rather than binding, and there was no complex formation. All of the proteins were structurally destabilized by the presence of phytate but were not denatured. From these findings, we predict that phytate would bind electrostatically to a wide variety of positively charged proteins in the stomach as well as to trypsin and chymotrypsin in the duodenum. Both binding reactions may compromise the digestion of the protein component in feed stuffs. Because the interaction between phytate and protein is electrostatic, the presence of anions, such as chloride, would nullify the antinutritional effect of phytate.