Phytase is a protein molecule that can be digested by endogenous proteases. Bacterial phytases have greater proteolytic resistence and affinity for IP6 compared to fungal phytases. Phytases from different sources have different molecular structures resulting in differences in activity, optimal pH, catalytic efficiency and thermostability.
Endogenous phytase activity occurs in the colons of pigs. Supplementing diets with exogenous phytase shifts phytase activity to the stomach and upper small intestine. The pH in a pig’s stomach is 2-2.5 while pH in the crop is 5.2-5.8. This difference in pH of the main phytase activity sites between species results in different catalytic efficiencies of the phytase enzyme.
Phytate level and its interaction with cations and proteins determines the amount and rate of insoluble mineral-phytate or protein-mineral-phytate complexes formed.