Molecular recognition of angiogenesis inhibitors fumagillin and ovalicin by methionine aminopeptidase 2

Angiogenesis inhibitors are a novel class of promising therapeutic agents f or treating cancer and other human diseases. Fumagillin and ovalicin compos e a class of structurally related natural products that potently inhibit an giogenesis by blocking endothelial cell proliferation, A synthetic analog o f fumagillin, TNP-470, is currently undergoing clinical trials for treatmen t of a variety of cancers, A common target for fumagillin and ovalicin rece ntly was identified as the type 2 methionine aminopeptidase (MetAP2), These natural products bind MetAP2 covalently, inhibiting its enzymatic activity . The specificity of this binding is underscored by the lack of inhibition of the closely related type 1 enzyme, MetAP1, The molecular basis of the hi gh affinity and specificity of these inhibitors for MetAP2 has remained und iscovered. To determine the structural elements of these inhibitors and Met AP2 that are involved in this interaction, we synthesized fumagillin analog s in which each of the potentially reactive epoxide groups was removed eith er individually or in combination, We found that the ring epoxide in fumagi llin is involved in the covalent modification of MetAP2, whereas the side c hain epoxide group is dispensable. By using a fumagillin analog tagged with fluorescein, His-231 in MetAP2 was identified as the residue that is coval ently modified by fumagillin, Site-directed mutagenesis of His-231 demonstr ated its importance for the catalytic activity of MetAP2 and confirmed that the same residue is covalently modified by fumagillin, These results, in a greement with a recent structural study, suggest that fumagillin and ovalic in inhibit MetAP2 by irreversible blockage of the active site.