Abstract
Two phytase isozymes (PHY1 and PHY2) were purified homogeneously from bran of Triticum aestivum L. cv. Nourin #61 by (NH4)2SO4 fractionation, methanol fractionation, Sephacryl S-200 HR gel filtration chromatography, DEAE-TOYOPEARL chromatography, CM-TOYOPEARL chromatography and second Sephacryl S-200 HR gel filtration chromatography. Molecular weights of the two enzymes were 71,000 and 66,000 by gel filtration, and 68,000 and 66,000 by SDS-PAGE, respectively. Optimum pH and temperatures were 6.0 and 45°C for PHY1, and 5.5 and 50°C for PHY2. The activity of both phytases was stable at pHs between pH 4.0-7.0 and below 40°C. The Km values for myo-inositol hexakisphosphate (IHP) were 0.48 μM for PHY1 and 0.77 μM for PHY2. The Ki values for Pi were 2.69 mM for PHY1 and 6.59 mM for PHY2. Both phytases showed relatively high specificity for IHP.
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