**2. Results**

Based on amino acid homology, secondary structures, bioinformatics, and polarity of the three domains D1, D2, and D3 of ACE2, all nineteen species were clustered. Note that, since ACE2 from Salmo salar is missing 119 N-terminal residues, this protein was not included in the analysis of the sequence conservation of the D1 (residues 24–42) and D2 domains (residues 79–84) involved in the interaction with SARS-CoV spike glycoprotein. Finally, a cumulative set of nineteen species clusters was built, among which the SARS-CoV-2 transmission may occur.
