Purification and properties of a phytase from Candida krusei WZ-001

A phytase from Candida krusei WZ-001 isolated from soil was purified to electrophoretic homogeneity by ion-exchange chromatography, hydrophobic interaction chromatography, and gel filtration. The phytase is composed of two different subunits with molecular masses of 116 kDa and 31 kDa on SDS-PAGE (or 120 kDa and 30 kDa on gel chromatography), with the larger subunit having a glycosylation rate of around 35%. The phytase has an optimum pH of 4.6, an optimum temperature of 40°C and a p I value of 5.5. The phytase activity was stimulated by 2-mercapto-ethanol and dithiothreitol (DTT), and inhibited by Zn 2+, Mg 2+, iodoacetate, p I value of 5.5. The phytase activity was stimulated by 2-mercapto-ethanol ethanol and dithiothreitol (DTT), and inhibited by Zn 2+, Mg 2+, iodoacetate, p-chroloromercuribenzoate ( pCMB) and phenylmethylsulfonyl fluoride (PMSF). The phytase displayed a broad substrate specificity and the K m for phytate was 0.03 mM. Phytate was sequentially hydrolyzed by the phytase. Furthermore, 1D and 2D NMR analyses and bioassay of myoinositol indicated that the end hydrolysis product of phytate was myoinositol 2-monophosphate.