title: Crystallographic snapshots of Aspergillus fumigatus phytase, revealing its enzymatic dynamics.
abstract: Understanding of the atomic movements involved in an enzymatic reaction needs structural information on the active and inactive native enzyme molecules and on the enzyme-substrate, enzyme-intermediate, and enzyme-product(s) complexes. By using the X-ray crystallographic method, four crystal structures of Aspergillus fumigatus phytase were obtained at resolution higher than 1.7 A. The pH-dependent catalytic activity of A. fumigatus phytase was linked to three water molecules that may prevent the substrate from binding and thus block nucleophilic attack of the catalytic imidazole nitrogen. Comparison of various structures also identified the water molecule that attacks the phosphamide bond during the hydrolysis process, and established the hydrolysis pathway of the intermediate. Additionally, two reaction product phosphates were observed at the active site, suggesting a possible product release pathway after hydrolysis of the intermediate. These results can help explain the catalytic mechanism throughout the whole acid phosphatase family, as all key residues are conserved.
authors.affiliation: Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Qun
authors.initials: Q
authors.lastname: Liu
authors.forename: Qingqiu
authors.initials: Q
authors.lastname: Huang
authors.forename: Xin Gen
authors.initials: XG
authors.lastname: Lei
authors.forename: Quan
authors.initials: Q
authors.lastname: Hao
mesh_terms: D010832:6-Phytase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001232:Aspergillus fumigatus / Q000201:enzymology*; D001665:Binding Sites; D018360:Crystallography, X-Ray; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D010710:Phosphates / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013379:Substrate Specificity; D014867:Water / Q000737:chemistry
chemical_list: D005656:Fungal Proteins; D010710:Phosphates; D014867:Water; D010832:6-Phytase