The angiotensin-converting enzyme 2 (ACE2) is an enzyme that plays a variety of physiological roles in the human body, belonging to the family of dipeptidyl carboxypeptidases of the angiotensin-converting enzyme. The protein primarily catalyzes the cleavage of angiotensin I into angiotensin 1-9 and the cleavage of angiotensin II into the vasodilator angiotensin 1-7, thereby regulating physiological processes such as blood pressure, fluid balance, inflammation, cell proliferation, hypertrophy, and fibrosis. Notably, ACE2 may play a role in regulating cardiovascular and renal functions as well as fertility, with its expression being organ- and cell-specific. Additionally, ACE2 serves as the functional receptor for the S protein of SARS and HCoV-NL63 human coronaviruses and is the cellular receptor for the novel coronavirus (COVID-19), which is of significant importance in the current global health crisis.