Crystal structures of a novel, thermostable phytase in partially and fully calcium-loaded states

• Published in: Nature structural & molecular biology Vol. 7; no. 2; pp. 147 - 153
• Main Authors: Oh, Byung-Ha, Ha, Nam-Chul, Oh, Byung-Chul, Shin, Sejeong, Kim, Hyun-Ju, Oh, Tae-Kwang, Kim, Young-Ok, Choi, Kwan Yong
• Format: Journal Article
• Language: English
• Published: United States Nature Publishing Group 01.02.2000
• Subjects: 6-Phytase - chemistry; 6-Phytase - genetics; 6-Phytase - metabolism; Amino acids; Base Sequence; Binding Sites; Calcium; Calcium - chemistry; Calcium - metabolism; Crystallography, X-Ray; Enzyme Activation; Enzyme Stability; Feeds; Models, Molecular; Molecular Sequence Data; Phytic Acid - chemistry; Phytic Acid - metabolism; Pollution control; Protein Conformation; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Recombinant Proteins - metabolism
• ISSN: 1072-8368; 1545-9993; 2331-365X; 1545-9985
• DOI: 10.1038/72421

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.