Effect of polar amino acid residue substitution by site-directed mutagenesis in the N-terminal domain of Pseudomonas sp. phytase on enzyme activity

Abstract

In aquatic environments with a neutral pH and low temperature, phytase used for decomposition of phytate should maintain high activity even at low temperatures. The N-terminal domain of the Pseudomonas sp. FB15 phytase which maintains high activity even at 25 °C increases low-temperature activity and catalytic efficiency. In this study, the three-dimensional structure of the N-terminal domain was predicted and substitutions for the amino acid residues of the region assumed to be the active site were made. The activity of mutants, in which alanine (A) was substituted for the original residue, was investigated at various temperatures and pH values. Significant differences in enzymatic activity were observed only in mutant E263A, suggesting that the amino acid residue at position 263 of the N-terminal domain is important in enzyme activity.