ACE2 and COVID-19: Functionally, there are two forms of ACE2, the full-length ACE2 that contains a structural transmembrane domain, which anchors its extracellular domain to the plasma membrane and soluble Angiotensin Converting Enzyme 2 (sACE2) that lacks the membrane anchor and circulates in small amounts in the blood [116], other RAAS-related therapy which has been approached for COVID-19 treatment.