title: Crystal structures of a novel, thermostable phytase in partially and fully calcium-loaded states.
abstract: Phytases hydrolyze phytic acid to less phosphorylated myo-inositol derivatives and inorganic phosphate. A thermostable phytase is of great value in applications for improving phosphate and metal ion availability in animal feed, and thereby reducing phosphate pollution to the environment. Here, we report a new folding architecture of a six-bladed propeller for phosphatase activity revealed by the 2.1 A crystal structures of a novel, thermostable phytase determined in both the partially and fully Ca2+-loaded states. Binding of two calcium ions to high-affinity calcium binding sites results in a dramatic increase in thermostability (by as much as approximately 30 degrees C in melting temperature) by joining loop segments remote in the amino acid sequence. Binding of three additional calcium ions to low-affinity calcium binding sites at the top of the molecule turns on the catalytic activity of the enzyme by converting the highly negatively charged cleft into a favorable environment for the binding of phytate.
authors.affiliation: Department of Life Science and School of Environmental Engineering, Pohang University of Science and Technology, Pohang, Kyungbuk, 790-784, South Korea.
authors.forename: N C
authors.initials: NC
authors.lastname: Ha
authors.forename: B C
authors.initials: BC
authors.lastname: Oh
authors.forename: S
authors.initials: S
authors.lastname: Shin
authors.forename: H J
authors.initials: HJ
authors.lastname: Kim
authors.forename: T K
authors.initials: TK
authors.lastname: Oh
authors.forename: Y O
authors.initials: YO
authors.lastname: Kim
authors.forename: K Y
authors.initials: KY
authors.lastname: Choi
authors.forename: B H
authors.initials: BH
authors.lastname: Oh
mesh_terms: D010832:6-Phytase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D004795:Enzyme Stability; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010833:Phytic Acid / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D010833:Phytic Acid; D010832:6-Phytase; D002118:Calcium