Role of calcium ions in the thermostability of thermolysin and Bacillus subtilis var. amylosacchariticus neutral protease.
Role of calcium ions in the thermostability of thermolysin and Bacillus subtilis var. amylosacchariticus neutral protease.
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钙离子在嗜热菌蛋白酶和枯草芽孢杆菌变种的热稳定性中的作用。
DOI：
10.1111/j.1432-1033.1976.tb10293.x
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发表时间：
1976
期刊：
影响因子：
--
通讯作者：
H. Okada
中科院分区：
文献类型：
--
作者：
M. Tajima;I. Urabe;K. Yutani;H. Okada
研究了钙离子对嗜热菌蛋白酶和枯草芽孢杆菌的稳定作用。研究了淀粉酶中性蛋白酶。通过用金属螯合剂平衡的Sephadex G-25凝胶过滤从蛋白酶中除去钙和锌离子。使用这些酶与不同的金属含量，热失活动力学进行了研究，在不同的温度。去除钙离子引起热稳定性急剧下降，并减少了热失活的活化焓（Δ H *）和熵（Δ S *）的值。含0.3 g-原子/mol的嗜热菌蛋白酶和B的稳定性几乎没有差别。枯草中性蛋白酶，含有1.4 g-原子/mol。用平衡凝胶色谱法测定了蛋白酶与不同浓度游离钙离子的钙结合等温线。嗜热菌蛋白酶有四个独立的钙结合位点，具有相同的内在结合常数（K）为2.0 × 10（4）M-1。B。枯草杆菌中性蛋白酶有四个独立的位点。三个位点的K值为1.1 × 10（5）M-1，另一个位点的结合常数为1.5 × 10（3）M-1。这些蛋白酶之间的钙结合的总自由能变化差异不大。从这些结果可以得出结论，钙对这些酶的稳定作用几乎是相等的，并且嗜热菌蛋白酶的额外热稳定性可能来自其多肽链结构。
The stabilizing effect of calcium ions on thermolysin and Bacillus subtilis var. amylosacchariticus neutral protease has been investigated. Calcium and zinc ions were removed from the proteases by gel filtration over Sephadex G-25 equilibrated with metal chelating agents. Using these enzymes with different metal content, heat inactivation kinetics were studied at various temperatures. Removal of calcium ions caused a sharp decrease in thermostability and diminished the values of the activation enthalpy (deltaH*) and entropy (deltaS*) for heat inactivation. There was little difference in stability between thermolysin containing 0.3 g-atom/mol and B. subtilis neutral protease containing 1.4 g-atoms/mol. Calcium binding isotherms of the proteases were obtained by equilibrium gel chromatography with various concentrations of free calcium ions. Thermolysin had four independent calcium binding sites with an identical intrinsic binding constant (K) of 2.0 X 10(4) M-1. B. subtilis neutral protease had four independent sites. The K value for three sites was 1.1 X 10(5) M-1 and the binding constant for the other site was 1.5 X 10(3) M-1. There was little difference in total free energy change for calcium binding between these proteases. From these results it is concluded that the stabilizing effect of calcium on these enzymes is almost equal, and the extra thermal stability of thermolysin is likely to come from its polypeptide chain structure.