Molecular dynamics study of the effect of calcium ions on the thermostability of Bacillus Amyloliquefaciens Phytase
Phytase is added to animal feeds to improve phosphorus absorption and reduce phosphorus excretion of swine and poultry. It hydrolyses phytate, which is a major form of storage of cereal grains and legumes in commercial animal feeds, into myo-inositol and inorganic phosphate. Adequate thermostabil...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
INSI Publications
2012
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| Subjects: | |
| Online Access: | http://irep.iium.edu.my/17995/ http://irep.iium.edu.my/17995/ http://irep.iium.edu.my/17995/1/B_Amyl_Phyt_AJBAS_2012_Jan_6_109-116.pdf |
| Summary: | Phytase is added to animal feeds to improve phosphorus absorption and reduce phosphorus
excretion of swine and poultry. It hydrolyses phytate, which is a major form of storage of cereal grains
and legumes in commercial animal feeds, into myo-inositol and inorganic phosphate. Adequate
thermostability of phytase is necessary for field application as diets for swine and poultry are normally
pelleted at high temperatures (60-80°C). In this study, Molecular Dynamics simulation (MD) was used
to study the effect of calcium metal ions on the thermostability of Bacillus amyloliquefacience phytase.
MD simulations of the enzyme in the calcium-loaded and calcium-free states were performed at 60°C
(333 K) and 80°C (353 K) in water as the solvent medium, for duration of 4 ns. Root mean square
deviations (RMSD) of calcium-bound residues, backbone atoms, and other secondary structures were
found to be lower in the presence of calcium ions at both temperatures. In addition, calcium-loaded
enzyme was found to have fewer numbers of hydrogen bonds and salt bridges at both temperatures, yet
calcium-loaded enzyme remains more thermostable due to network of electrostatic interactions
induced by calcium binding. The binding effect of calcium ions becomes weaker at 80°C and the small
increase of binding effect offered by the calcium ions at higher temperatures in not sufficient enough to
maintain the activity at this temperature. It is proposed that suitable mutations at the coil region would
lead to increase in the stability of the enzyme at high temperatures.
Key words: Bacillus amyloliquefaciens phytase, Molecular Dynamics simulation, calcium ions,
thermostability, RMSD, hydrogen bonds, salt bridges. |
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