Department of Organic Chemistry, University of Debrecen, P.O. Box 400, H-4002 Debrecen, Hungary.
School of Pharmacy & Biomedical Sciences, University of Central Lancashire, Preston PR1 2HE, UK.
Molecules. 2023 Mar 28;28(7):3005. doi: 10.3390/molecules28073005.
Glycogen phosphorylase (GP) is a key regulator of glucose levels and, with that, an important target for the discovery of novel treatments against type 2 diabetes. β-d-Glucopyranosyl derivatives have provided some of the most potent GP inhibitors discovered to date. In this regard, -β-d-glucopyranosyl azole type inhibitors proved to be particularly effective, with 2- and 4-β-d-glucopyranosyl imidazoles among the most potent designed to date. His377 backbone C=O hydrogen bonding and ion-ion interactions of the protonated imidazole with Asp283 from the 280s loop, stabilizing the inactive state, were proposed as crucial to the observed potencies. Towards further exploring these features, 4-amino-3-(β-d-glucopyranosyl)-5-phenyl-1-pyrazole () and 3-(β-d-glucopyranosyl)-4-guanidino-5-phenyl-1-pyrazole () were designed and synthesized with the potential to exploit similar interactions. Binding assay experiments against rabbit muscle GPb revealed as a moderate inhibitor (IC = 565 µM), but displayed no inhibition at 625 µM concentration. Towards understanding the observed inhibitions, docking and post-docking molecular mechanics-generalized Born surface area (MM-GBSA) binding free energy calculations were performed, together with Monte Carlo and density functional theory (DFT) calculations on the free unbound ligands. The computations revealed that while was predicted to hydrogen bond with His377 C=O in its favoured tautomeric state, the interactions with Asp283 were not direct and there were no ion-ion interactions; for , the most stable tautomer did not have the His377 backbone C=O interaction and while ion-ion interactions and direct hydrogen bonding with Asp283 were predicted, the conformational strain and entropy loss of the ligand in the bound state was significant. The importance of consideration of tautomeric states and ligand strain for glucose analogues in the confined space of the catalytic site with the 280s loop in the closed position was highlighted.
糖原磷酸化酶 (GP) 是血糖水平的关键调节剂，因此也是发现 2 型糖尿病新型治疗方法的重要靶点。β-d-吡喃葡萄糖基衍生物提供了迄今为止发现的最有效的 GP 抑制剂之一。在这方面，-β-d-吡喃葡萄糖基唑类抑制剂被证明特别有效，其中 2-和 4-β-d-吡喃葡萄糖基咪唑是迄今为止设计出的最有效的抑制剂之一。His377 骨架 C=O 氢键和质子化咪唑与 280s 环中的 Asp283 的离子-离子相互作用，稳定了无活性状态，被认为是观察到的效力的关键。为了进一步探索这些特征，设计并合成了 4-氨基-3-(β-d-吡喃葡萄糖基)-5-苯基-1-吡唑 () 和 3-(β-d-吡喃葡萄糖基)-4-胍基-5-苯基-1-吡唑 ()，它们有可能利用类似的相互作用。对兔肌肉 GPb 的结合实验表明 是一种中等抑制剂（IC = 565 µM），但在 625 µM 浓度下没有显示出抑制作用。为了理解观察到的抑制作用，进行了对接和对接后分子力学-广义 Born 表面面积 (MM-GBSA) 结合自由能计算，以及对游离未结合配体的蒙特卡罗和密度泛函理论 (DFT) 计算。计算结果表明，虽然 被预测在其有利的互变异构体状态下与 His377 C=O 形成氢键，但与 Asp283 的相互作用不是直接的，也没有离子-离子相互作用；对于 ，最稳定的互变异构体没有 His377 骨架 C=O 相互作用，虽然预测了离子-离子相互作用和与 Asp283 的直接氢键，但配体在结合状态下的构象应变和熵损失很大。突出强调了在封闭的 280s 环位置下考虑糖类似物的互变异构体状态和配体应变对于催化位点受限空间的重要性。
