PMC

SDS-polyacrylamide gels of FTE (A), FTEII (B), and FBA (C) phytases concentrated by ultrafiltration and treated with or without endo H_f. Lanes M, molecular size marker. (A) Lanes: 1, endo H_f; 2, FTE treated with endo H_f; 3, FTE without endo H_f treatment. (B) Lanes: 1, FTEII treated with endo H_f; 2, endo H_f; 3, FTEII without endo H_f treatment. (C) Lanes: 1, FBA treated with endo H_f; 2, FBA without endo H_f treatment; 3, endo H_f.

Effects of pH (A) and temperature (B) on specific phytase activity at 37°C and pH 7.5 for FTE (□), FTEII (▪), and FBA (•). Points represent the means for at least three independent enzyme assays (coefficient of variation, <5%).

(A) Molecular model of FTEII constructed by homology modeling using SWISS-MODEL 8.05, with the 2POO structure as a template. (B) Hydrogen bond between T37 and K361 in the structure for FTE, FTEII, and FBA, binding the ninth residue from the N-terminal end with the alpha helix of the protein. (C) P257 in a surface loop in FTE, FTEII, and FBA. (D) Salt bridges between D336 and a Ca²⁺ ion or K351 in FTEII, FBA, and PhyC. Other salt bridges with the Ca²⁺ ion are also shown.

Residual activities of FTE (□), FTEII (▪), FBA (•), and PhyC-R (○) after 10 min of heat treatment at pH 7.5 (A and B) or 5.5 (C and D) in the presence of 1.0 (A and C) or 5.0 (B and D) mM CaCl₂. Points represent the means for at least three independent determinations (coefficient of variation, <5%).