Figure 8: View of the three-dimensional structure of the human methylmalonyl- CoA mutase enzyme models built on the basis of experimental structure of the α chain of the P. shermanii enzyme (PDB 1REQ) and human MCM enzyme (PDB 3BIC and 2XIQ) by Modeller 9.11, showing increased size and steric clash made by hydrophobic positively charged Lys residue located in position 165 in the extreme N-terminal extension.