On the other hand, the peptidase domain of ACE2 has a claw-like structure with two lobes. The enzymatic active site of ACE2 is burried  in a cavity surrounded by the two lobes SARS-CoV S1-CTD binds to the outer surface of the N-terminal lobe, away from the peptidase active site. Consequently, SARS-CoV binding has no effect on the enzymatic activity of ACE2 and vice versa.