SARS-CoV-2 infection depend on the binding of the viral Spike glycoprotein (S) to the human receptor Angiotensin Converting Enzyme 2 (ACE2) to induce virus-cell membrane fusion. S protein evolved diverse amino acid changes that are possibly linked to more efficient binding to human ACE2, which might explain part of the increase in frequency of SARS-CoV-2 Variants Of Concern (VOCs). In this work, we investigated the role of ACE2 protein variations that are naturally found in human populations and its binding affinity with S protein from SARS-CoV-2 representative genotypes, based on a series of in silico approaches involving molecular modelling, docking and molecular dynamics simulations. Our results indicate that SARS-CoV-2 VOCs bind more efficiently to the human receptor ACE2 than the ancestral Wuhan genotype. Additionally, variations in the ACE2 protein can affect SARS-CoV-2 binding and protein-protein stability, mostly making the interaction weaker and unstable in some cases. We show that some VOCs, such as B.1.1.7 and P.1 are much less sensitive to ACE2 variants, while others like B.1.351 appear to be specifically optimized to bind to the widespread wild-type ACE2 protein.Communicated by Ramaswamy H. Sarma.