The hydrolysis of phytic acid, the principal storage form of phosphorus in seeds and pollen, to myo-inositol and phosphoric acid is a very important metabolic process in many biological systems. This dephosphorylation of free or bound inositol phosphate is believed to be mainly affected by phytase. Generally, phytase behaves like a monomeric protein of a molecular mass of approximately 40-200 kDa and shows a broad substrate specificity with optimal degradation of phytate occurring around pH 4.5-6.0 and a temperature at 45-60 degrees C. Furthermore, it is Sound that the Aspergillus ficuum phytase consists of 594 amino acid residues and the secondary structure contains 17.3% alpha-helixes, 29% beta-sheet, 32.6% turns, and 24.7% coils. The N-linked mannose and galactose of intact phytase from A. ficuum account for 27.3% of the molecular weight. This implies that the enzyme is a glycoprotein. Recently, the crystal structure of this phytase has been determined at 2.5 Angstrom resolution. In this review, the properties of various phytases are summarized and the digestion of phytate by phytase and its products are also discussed.