Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, India.
Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, India.
J Biomol Struct Dyn. 2021 Sep;39(15):5438-5448. doi: 10.1080/07391102.2020.1796789. Epub 2020 Jul 28.
Most β-Glucosidase (B8CYA8) are prone to inhibition by glucose. Experimentally observed specific activity of B8CYA8 on 20 mM, 50 mM, and 100 mM -nitrophenyl-β-D-glucopyranoside (NPGlc) substrate concentrations show surprise dependence on the presence of 0-3 M glucose at 335 K. We found that at high substrate concentration, the enzyme shows stimulation in specific activity with glucose and the glucose inhibition curve shifts toward the right with the increase in the substrate concentration. We employed atomistic molecular dynamics simulations of β-Glucosidase from at different glucose and NPGlc concentrations to provide microscopic explanations to the experimentally observed non-monotonic glucose concentration dependence of the enzyme activity. Our results show that accumulation of substrate (NPGlc) near the B8CYA8 catalytic site residues E166 and E354 and in the active site tunnel increases up to 0.5 M glucose when the specific activity is the highest. The number of NPGlc in the tunnel decreases drastically when glucose concentration is more than 0.5 M, and hence the specific activity decreases. Potential of mean force (PMF) calculations showed that the most favorable interaction between NPGlc and β-Glucosidase exists at 0.5 M glucose while at deficient and high glucose concentrations, the binding energy between the substrate and β-Glucosidase is very low. These studies provide the molecular basis towards understanding inhibition and stimulation of β-Glucosidase activity in the presence of glucose and may enable the optimum use of enzymes for the efficient conversion of high biomass loading saccharification reactions.Communicated by Ramaswamy H. Sarma.
大多数β-葡萄糖苷酶（B8CYA8）容易受到葡萄糖的抑制。在 335K 下，实验观察到 B8CYA8 在 20mM、50mM 和 100mM -硝基苯-β-D-吡喃葡萄糖苷（NPGlc）底物浓度下的比活性对 0-3M 葡萄糖的存在表现出惊人的依赖性。我们发现，在高底物浓度下，酶的比活性随着葡萄糖的存在而增加，并且随着底物浓度的增加，葡萄糖抑制曲线向右侧移动。我们采用来自 的β-葡萄糖苷酶的原子分子动力学模拟，在不同的葡萄糖和 NPGlc 浓度下，提供了对实验观察到的酶活性与葡萄糖浓度的非单调依赖性的微观解释。我们的结果表明，当比活性最高时，底物（NPGlc）在 B8CYA8 催化位点残基 E166 和 E354 附近以及活性位点隧道中积累增加到 0.5M 葡萄糖。当葡萄糖浓度超过 0.5M 时，隧道中 NPGlc 的数量急剧减少，因此比活性降低。平均力势（PMF）计算表明，NPGlc 与β-葡萄糖苷酶之间最有利的相互作用存在于 0.5M 葡萄糖中，而在葡萄糖缺乏和高浓度时，底物与β-葡萄糖苷酶之间的结合能非常低。这些研究为理解葡萄糖存在下β-葡萄糖苷酶活性的抑制和刺激提供了分子基础，并可能使酶在高效转化高生物质负荷糖化反应中得到最佳利用。由 Ramaswamy H. Sarma 传达。
