"Binds 2 divalent metal cations per subunit. Has a high-affinity and a low affinity metal-binding site. The true nature of the physiological cofactor is under debate. The enzyme is active with cobalt, zinc, manganese or divalent iron ions. Most likely, methionine aminopeptidases function as mononuclear Fe(2+)-metalloproteases under physiological conditions, and the catalytically relevant metal-binding site has been assigned to the histidine-containing high-affinity site."xsd:string