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

Abstract

Phytate-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.

Effect of germination on the phytase activity, phytate and total phosphorus contents of rice (Oryza sativa), maize (Zea mays), millet (Panicum miliaceum), sorghum (Sorghum bicolor) and wheat (Triticum aestivum)

“…During the germination of cereals, phytate is degraded by intrinsic phytase enzyme (Kumar et al 2010). Naturally, there are dissimilarities in the capacities of various plant and microbial species to dephosphorylate phytate, due to differences in their intrinsic phytatedegrading activities (Egli et al 2002) and the properties of the enzymes, such as protein stability and pH, as well as temperature optimum for phytate degradation (Konietzny and Greiner 2002). The degree of illumination during germination has been found to be an important factor in the reduction of phytates, with germinating under blue or red light being more effective than germinating in the dark (Khattak et al 2007).…”

Purification and characterisation of an extracellular phytase from Aspergillus niger 11T53A9

“…In addition, dietary myo-inositol phosphates have been suggested to bring about benefits for human health, such as amelioration of heart disease conditions by controlling hypercholesterolemia and atheriosclerosis (14), prevention of renal stone formation (8), and protection against a variety of cancers, in particular colon cancer (31). activity has been detected in plants, micro-organisms, and in some animal tissues (15,30) and phytases from several plant and microbial species have been purified and characterised.…”

“…From these studies it was concluded that the phosphate residue at position C-2 of the myo-inositol is resistant to dephosphorylation by phytases (15). There was only one exception reported so far in the scientific literature.…”

Phytases Improve Myo-Inositol Bioaccessibility in Rye Bread: A Study Using an In Vitro Method of Digestion and a Caco-2 Cell Culture Model

“…Enzymatic methods of phytate degradation in foods and feeds have gained considerable interest, regarding their numerous advantages over physical or chemical methods (2). Phyta ses, phosphohydrolases of myo-inositol hexakisphosphate, hydrolyse phytate to a pool of lower myo-inositol phosphates (3,4). In breadmaking, phosphorolytic activity originates from wheat or rye fl our enzymes as well as from the yeast phytase (5)(6)(7).…”

“…There are 3-phytases A (myo-inositol hexakisphosphate 3-phos phohydrolase, EC 3.1.3.8), which start catalytic action at C3 atom of the myo-inositol ring, 6-phytases A (myo-inositol h exaphosphate 6-phosphohydrolase, EC 3.1.3.26), which initiate the hydrolysis at the C6, and phytases B (EC 3.1. 3.2), non -specifi c acid phosphomonoesterases (3). Generally, p hytases A are not able to hydrolyse phosphate residue at the C2 of the myo-inositol ring.…”