ABSTRACT
PHYTASES are phosphatases that can utilize phytate (myo-inositol hexakis-phosphate; Ins(1,2,3,4,5,6)P6 as a substrate. Phytate and phytases appear to be ubiquitous in nature and likely exist in all types of cells [1,2,3]. Because they exhibit considerably greater phytate-cleaving activity than the phytases from animal cells, plant and microbial phytases are utilized industrially to degrade the phytate in foods and feeds. The specificity difference in the initial phosphate removed by the best studied plant and fungal phytases is shown in Figure 7.1. Triticum aestivum (wheat) phytase preferentially hydrolyzes the phosphate at position 4, whereas Aspergillus niger phytase first cleaves mainly at position 3 [4,5]. The remaining phosphates are also removed by these enzymes, but inositol 2-monophosphate tends to accumulate at the end of the reaction rather than free myo-inositol [4,6]. The functional significance of the differences in product specificity of the various phytases is currently unknown.
