Molecular and catalytic properties of phytate‐degrading enzymes (phytases)

Abstract

SummaryPhytate‐degrading enzymes catalyse the step‐wise release of phosphate from phytate, the principle storage form of phosphorus in plant seeds and pollen. They are widespread in nature, occurring in plants and micro‐organisms, as well as in some animal tissues. Phytate‐degrading enzymes have been studied intensively in recent years because of the great interest in such enzymes for reducing phytate content in animal feed and food for human consumption. Phytate‐degrading enzymes are also of interest for producing defined breakdown products of phytate for kinetic and physiological studies. Certain myo‐inositol phosphates have been proposed to have novel metabolic effects and therefore, the physiological role of different myo‐inositol phosphates is presently undergoing extensive research. Generally, phytase behaves like a monomeric enzyme with molecular masses between 40 and 70 kDa. Up to now, two main types of phytate‐degrading enzymes have been identified; acid phytate‐degrading enzymes with an pH optimum around pH 5 and alkaline phytate‐degrading enzymes with an pH optimum around pH 8. Most of the so far described phytate‐degrading enzymes belong to the acidic type, and their optimal pH ranges from 4.5 to 6.0. This review summarises the molecular features as well as catalytic properties of phytate‐degrading enzymes and also discusses enzymatic phytate degradation.