3AMR: Crystal Structures Of Bacillus Subtilis Alkaline Phytase In Complex With Ca2+, Co2+, Ni2+, Mg2+ And Myo-inositol Hexasulfate

Alkaline phytases from Bacillus species, which hydrolyze phytate to less phosphorylated myo-inositols and inorganic phosphate, have great potential as additives to animal feed. The thermostability and neutral optimum pH of Bacillus phytase are attributed largely to the presence of calcium ions. Nonetheless, no report has demonstrated directly how the metal ions coordinate phytase and its substrate to facilitate the catalytic reaction. In this study, the interactions between a phytate analog (myo-inositol hexasulfate) and divalent metal ions in Bacillus subtilis phytase were revealed by the crystal structure at 1.25 A resolution. We found all, except the first, sulfates on the substrate analog have direct or indirect interactions with amino acid residues in the enzyme active site. The structures also unraveled two active site-associated metal ions that were not explored in earlier studies. Significantly, one metal ion could be crucial to substrate binding. In addition, binding of the fourth sulfate of the substrate analog to the active site appears to be stronger than that of the others. These results indicate that alkaline phytase starts by cleaving the fourth phosphate, instead of the third or the sixth that were proposed earlier. Our high-resolution, structural representation of Bacillus phytase in complex with a substrate analog and divalent metal ions provides new insight into the catalytic mechanism of alkaline phytases in general.
PDB ID: 3AMRDownload
MMDB ID: 89811
PDB Deposition Date: 2010/8/22
Updated in MMDB: 2011/05
Experimental Method:
x-ray diffraction
Resolution: 1.25  Å
Source Organism:
Similar Structures:
Biological Unit for 3AMR: monomeric; determined by author and by software (PISA)
Molecular Components in 3AMR
Label Count Molecule
Protein (1 molecule)
Molecule annotation
Chemicals (12 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB