[7] Furthermore, MetAP2 is of particular interest because the enzyme plays a key role in angiogenesis, the growth of new blood vessels, which is necessary for the progression of diseases including solid tumor cancers and rheumatoid arthritis.

In E. coli (prokaryote), an enzyme called formylmethionine deformylase can cleave the formyl group, leaving just the N-terminal methionine residue.

The active site of MetAP2 has a structural motif characteristic of many metalloenzymes—including the dioxygen carrier protein, hemerythrin; the dinuclear non-heme iron protein, ribonucleotide reductase; leucine aminopeptidase; urease; arginase; several phosphatases and phosphoesterases—that includes two bridging carboxylate ligands and a bridging water or hydroxide ligand.

[10][19][28] The catalytic mechanisms of hydrolase enzymes depend greatly on the identity of the bridging ligand,[29] which can be challenging to determine due to the difficulty of studying hydrogen atoms via x-ray crystallography.

The histidine residues shown in the mechanism to the right, H178 and H79, are conserved in all MetAPs (MetAP1s and MetAP2s) sequenced to date, suggesting their presence is important to catalytic activity.

[30] Based upon X-ray crystallographic data, histidine 79 (H79) has been proposed to help position the methionine residue in the active site and transfer a proton to the newly exposed N-terminal amine.

[13][20][32][33][34] Specifically, the covalent binding of either the ovalicin or fumagillin epoxide moiety to the active site histidine residue of MetAP2 has been shown to inactivate the enzyme, thereby inhibiting angiogenesis.

Nevertheless, with both the growth and metastasis of solid tumors depending heavily on angiogenesis, fumagillin and its analogs—including evexomostat, TNP-470, caplostatin, and beloranib—as well as ovalicin represent potential anticancer agents.