Angiotensin I converting enzyme (ACE), also known as dipeptidyl peptidase A, is a zinc metallopeptidase of great significance for blood pressure control and water salt metabolism. ACE converts angiotensin I into angiotensin II by releasing the terminal His Leu dipeptide, thereby increasing the vasoconstrictive activity of angiotensin. It can also inactivate bradykinin, which is an effective vasodilator. ACE and ACE-2 are two cell surface proteases that are important regulators of the renin angiotensin system (RAS) and play a crucial role in maintaining mammalian blood pressure homeostasis and water salt balance. ACE exists in two forms in the human body, one expressed in somatic cells called sACE (physiological  ACE), and the other expressed in germ cells called gACE (genetic  ACE). The main difference between the two forms of ACE is that gACE only contains one C-terminal active functional region, while sACE contains two active functional regions, the C-terminal and N-terminal. Therefore, the catalytic activity of the two ACEs is different, and in the most important RAS boost regulation system, sACE plays a more critical role. ACE-2 is composed of a protease domain and is an important regulator of cardiopulmonary function. It is also a cellular receptor for the spike protein of SARS virus and COVID-19, which cause severe acute respiratory syndrome.