The interaction between the angiotensin-converting enzyme 2 (ACE2) and the receptor binding domain (RBD) of the spike protein from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) plays a pivotal role in virus entry into the host cells. Since recombinant ACE2 protein has been suggested as an anti-SARS-CoV-2 therapeutic agent, this study was conducted to design an ACE2 protein with more desirable properties. In this regard, the amino acids with central roles in enzymatic activity of the ACE2 were substituted. Moreover, saturation mutagenesis at the interaction interface between the ACE2 and RBD was performed to increase their interaction affinity. The best mutations to increase the structural and thermal stability of the ACE2 were also selected based on B factors and mutation effects. The obtained resulted revealed that the Arg273Gln and Thr445Gly mutation have drastically reduced the binding affinity of the angiotensin-II into the active site of ACE2. The Thr27Arg mutation was determined to be the most potent mutation to increase the binding affinity. The Asp427Arg mutation was done to decrease the flexibility of the region with high B factor. The Pro451Met mutation along with the Gly448Trp mutation was predicted to increase the thermodynamic stability and thermostability of the ACE2. The designed therapeutic ACE2 would have no enzymatic activity while it could bear stronger interaction with Spike glycoprotein of the SARS-CoV-2. Moreover, decreased in vivo enzymatic degradation would be anticipated due to increased thermostability. This engineered ACE2 could be exploited as a novel therapeutic agent against COVID-19 after necessary evaluations.

血管紧张素转换酶 2 (ACE2) 与严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) 刺突蛋白的受体结合域 (RBD) 之间的相互作用在病毒进入宿主细胞中发挥着关键作用。由于重组 ACE2 蛋白已被建议作为抗 SARS-CoV-2 治疗剂，因此本研究旨在设计具有更理想特性的 ACE2 蛋白。在这方面，在 ACE2 酶活性中起核心作用的氨基酸被取代。此外，在ACE2和RBD之间的相互作用界面处进行饱和诱变以增加它们的相互作用亲和力。还根据 B 因素和突变效应选择了提高 ACE2 结构和热稳定性的最佳突变。所得结果表明Arg273Gln和Thr445Gly突变显着降低了血管紧张素-II与ACE2活性位点的结合亲和力。 Thr27Arg 突变被确定为增加结合亲和力最有效的突变。 Asp427Arg 突变是为了降低具有高 B 因子的区域的灵活性。 Pro451Met 突变与 Gly448Trp 突变预计会提高 ACE2 的热力学稳定性和热稳定性。设计的治疗性ACE2没有酶活性，但可以与SARS-CoV-2的Spike糖蛋白产生更强的相互作用。此外，由于热稳定性增加，预计体内酶降解会减少。经过必要的评估后，这种工程化的 ACE2 可以被用作对抗 COVID-19 的新型治疗剂。