Analyzing the Binding of Co(II)-specific Inhibitors to the Methionyl Aminopeptidases from <em>Escherichia coli</em> and <em>Pyrococcus furiosus</em>

Methionine aminopeptidases (MetAPs) represent a unique class of protease that is capable of the hydrolytic removal of an N-terminal methionine residue from nascent polypeptide chains. MetAPs are physiologically important enzymes; hence, there is considerable interest in developing inhibitors that can be used as anti-angiogenic and antimicrobial agents. A detailed kinetic and spectroscopic study has been performed to probe the binding of a triazole-based inhibitor and a bestatin-based inhibitor to both Mn(II)and Co(II)-loaded type-I (Escherichia coli) and type-II (Pyrococcus furiosus) MetAPs. Both inhibitors were found to be moderate competitive inhibitors. The triazole-type inhibitor was found to interact with both active-site metal ions, while the bestatin-type inhibitor was capable of switching its mode of binding depending on the metal in the active site and the type of MetAP enzyme.