The invention provides a synthetic phytase polypeptide which encodes an enzymatically susceptible phytase. Also provided are feed or food products comprising an enzymatically susceptible phytase, and transgenic plants which express the enzymatically susceptible phytase. Further provided are methods for making and using enzymatically susceptible phytases, e.g., a method of using an enzymatically susceptible phytase in feed and food processing.