Types of phytases
Currently, four classes of phosphatase enzymes are known to include representatives that can degrade phytate: (1) Histidine Acid Phosphatase (HAP), (2) Purple Acid Phosphatase (PAP), (3) Cysteine Phosphatase (CP) and (4) β-Propellar Phytase (BPP). However, not all classes can effectively utilize phytate as a substrate. Each phytase type has unique structural features due to their distinct catalytic apparatus that allows them to utilize phytate as a substrate in various environments. In plants, only phytases belonging to the HAP and PAP groups have been identified and the current review will only discuss the major features of these phosphatases. Detailed descriptions about the CP and BPP phytase can be found elsewhere ( Lei et al., 2007).