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首页> 外文期刊>Journal of Molecular Biology >Crystal structures of Bacillus alkaline phytase in complex with divalent metal ions and inositol hexasulfate.
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Crystal structures of Bacillus alkaline phytase in complex with divalent metal ions and inositol hexasulfate.

机译：芽孢杆菌碱性植酸酶的晶体结构与二价金属离子和肌醇六硫酸盐复合。

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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.
机译：芽孢杆菌属的碱性肌醇六磷酸酶可将肌醇六磷酸水解为磷酸化程度较低的肌醇和无机磷酸盐，具有作为动物饲料添加剂的巨大潜力。芽孢杆菌肌醇六磷酸酶的热稳定性和中性的最佳pH值主要归因于钙离子的存在。然而，没有报道直接证明金属离子如何与植酸酶及其底物配位以促进催化反应。在这项研究中，枯草芽孢杆菌植酸酶中的植酸类似物（肌醇六硫酸盐）和二价金属离子之间的相互作用是通过1.25 A分辨率的晶体结构揭示的。我们发现，除了第一个以外，所有底物类似物上的硫酸盐都与酶活性位点的氨基酸残基具有直接或间接的相互作用。该结构还解开了两个与活性位点相关的金属离子，这在早期研究中并未探讨。重要的是，一种金属离子对于底物结合至关重要。另外，底物类似物的第四硫酸盐与活性位点的结合似乎比其他结合位点更强。这些结果表明碱性肌醇六磷酸酶是通过裂解第四种磷酸盐而不是先前提出的第三种或第六种磷酸盐开始的。我们对芽孢杆菌肌醇六磷酸酶与底物类似物和二价金属离子复合的高分辨率结构表示，为一般碱性肌醇六磷酸酶的催化​​机理提供了新的见解。

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