Post Graduate Department of Biotechnology, Utkal University, Bhubaneswar 751014, Odisha, India.
CSIR-Institute of Minerals & Materials Technology, Bhubaneswar 751013, Odisha, India; Academy of Scientific & Innovative Research, New Delhi 110025, India.
Int J Biol Macromol. 2018 Aug;115:853-860. doi: 10.1016/j.ijbiomac.2018.04.116. Epub 2018 Apr 24.
We have investigated the effects of lanthanum chloride (LaCl) on catalytic activity and conformation of bovine liver catalase (BLC) in different buffer solutions in vitro at 25 °C. Higher concentration of the salt caused decrease in catalase activity in the following order, HEPES > MOPS > Tris > Phosphate buffer. Results obtained from circular dichroism, fluorescence and absorption spectroscopy and from computational docking studies indicate that reduction in activity of BLC by LaCl is due to induction of conformational changes. Lanthanum-induced reduced BLC activity in MOPS, HEPES and Tris buffer is characterized by a significant loss in native fluorescence and increase in absorbance spectra of BLC. Nevertheless, the change in secondary conformation of BLC was maximum in HEPES and MOPS followed by Tris and least in Phosphate buffer. Therefore, the significant loss of BLC activity in phosphate buffer at higher molar concentration of lanthanum is attributed to the change in buffering capacity of the buffer. The conformational transition of BLC by LaCl was followed as a function of concentration. Therefore, the reduced BLC activity is directly controlled by lanthanum-induced conformational change of BLC in HEPES, MOPS and Tris buffer and indirectly controlled by the change in buffering capacity of the phosphate buffer.
我们研究了氯化镧（LaCl）对牛肝过氧化氢酶（BLC）在不同缓冲液中的体外催化活性和构象的影响，实验温度为 25°C。在更高浓度的盐存在下，过氧化氢酶活性按以下顺序降低：HEPES＞MOPS＞Tris＞磷酸盐缓冲液。圆二色性、荧光和吸收光谱以及计算对接研究的结果表明，LaCl 诱导的 BLC 活性降低是由于构象变化的诱导。LaCl 诱导的 MOPS、HEPES 和 Tris 缓冲液中 BLC 活性降低的特征是天然荧光显著损失和 BLC 吸收光谱增加。然而，BLC 二级构象的变化在 HEPES 和 MOPS 中最大，其次是 Tris，在磷酸盐缓冲液中最小。因此，在较高摩尔浓度的镧存在下，磷酸盐缓冲液中 BLC 活性的显著降低归因于缓冲能力的变化。BLC 的构象转变随浓度而变化。因此，BLC 在 HEPES、MOPS 和 Tris 缓冲液中的 LaCl 诱导构象变化直接控制着降低的 BLC 活性，而磷酸盐缓冲液的缓冲能力变化则间接地控制着 BLC 活性。
