Angiotensin-Converting Enzyme 2 (ACE2) is a transmembrane protein found in the lungs, intestines, heart, kidney, liver and arteries that plays a central role in vascular, renal, and myocardial physiology. The normal function of ACE2 is to convert the inactive vasoconstrictor angiotensin I (AngI) to Ang1-9 and the active form AngII to Ang1-7. It is involved in controlling vascular function including blood pressure, and absence of ACE2 expression in ace2-/ace2- mice leads to severely reduced cardiac contractility, indicating its importance in regulating heart function. ACE2 is also the primary attachment receptor for HCoV-N63, SARS-CoV and SARS-CoV-2. The S1 portion of the coronavirus spike protein attaches to ACE2 presented on the host cell surface. The SARS-CoV-2 virus targets pneumocytes and macrophages expressing ACE2 in the lung, and it is believed to infect ACE2-positive cells in other tissues including the gastrointestinal tract and potentially the liver (in cholangiocytes).
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