Angiotensin-converting enzyme 2 (ACE2) is not only an enzyme but also a functional receptor on cell membrane for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Here, the activity of ACE2 in single living cell is firstly determined using a nanokit coupled electrospray ionization mass spectrometry (nanokit-ESI-MS). Upon the insertion of a micro-capillary into the living hACE2-CHO cell and the electrochemical sorting of the cytosol, the target ACE2 enzyme hydrolyses angiotensin II inside the capillary to generate angiotensin 1–7. After the electrospray of the mixture at the tip of the capillary, the product is differentiated from the substrate in molecular weight to achieve the detection of ACE2 activity in single cells. The further measurement illustrates that the inflammatory state of cells does not lead to the significant change of ACE2 catalytic activity, which elucidates the relationship between intracellular ACE2 activity and inflammation at single cell level. The established strategy will provide a specific analytical method for further studying the role of ACE2 in the process of virus infection, and extend the application of nanokit based single cell analysis.

血管紧张素转换酶2（ACE2）不仅是一种酶，也是严重急性呼吸综合征冠状病毒2（SARS-CoV-2）细胞膜上的功能受体。在这里，首先使用 Nanokit 耦合电喷雾电离质谱 (nanokit-ESI-MS) 测定单个活细胞中 ACE2 的活性。将微毛细管插入活的 hACE2-CHO 细胞并对细胞质进行电化学分选后，目标 ACE2 酶会水解毛细管内的血管紧张素 II，生成血管紧张素 1-7。将混合物电喷雾到毛细管尖端后，产物与底物在分子量上进行区分，从而实现单细胞中ACE2活性的检测。进一步的测量表明细胞的炎症状态并没有导致ACE2催化活性的显着变化，这在单细胞水平上阐明了细胞内ACE2活性与炎症之间的关系。所建立的策略将为进一步研究ACE2在病毒感染过程中的作用提供具体的分析方法，并扩展基于纳米试剂盒的单细胞分析的应用。