Purification, crystallization and preliminary X-ray analysis of the Escherichia coli phytase

A recombinant form of Escherichia coli phytase, which hydrolyzes phytic acid into phosphate and myo-inositol, has been expressed, purified and crystallized. Crystals have been obtained by the method of bulk crystallization in 10 mM sodium acetate buffer (pH 4.5) without using a conventional precipitant. The enzyme crystallized in space group P2(1), with unit-cell dimensions a = 74.9, b = 72.2, c = 82.4 Angstrom, and beta = 92.0 degrees. Crystals diffract to at least 2.2 Angstrom at a rotating-anode X-ray source and a 2.3 Angstrom resolution data set has been collected, giving completeness of 98.0% and an R-sym of 0.072. Assuming there are two phytase molecules in the asymmetric unit, the solvent content is calculated to be 42.1%. A self-rotation function shows a clear twofold non-crystallographic symmetry relating two molecules of E. coli phytase in the asymmetric unit.