Hydroxamic Acids as Potent Inhibitors of Fe^II and Mn^IIE. coli Methionine Aminopeptidase: Biological Activities and X‐ray Structures of Oxazole Hydroxamate–EcMetAP‐Mn Complexes

Abstract

New series of acids and hydroxamic acids linked to five-membered heterocycles including furan, oxazole, 1,2,4- or 1,3,4-oxadiazole, and imidazole were synthesized and tested as inhibitors against the Fe(II) , Co(II) , and Mn(II) forms of E. coli methionine aminopeptidase (MetAP) and as antibacterial agents against wild-type and acrAB E. coli strains. 2-Aryloxazol-4-ylcarboxylic acids appeared as potent and selective inhibitors of the Co(II) MetAP form, with IC(50) values in the micromolar range, whereas 5-aryloxazol-2-ylcarboxylic acid regioisomers and 5-aryl-1,2,4-oxadiazol-3-ylcarboxylic acids were shown to be inefficient against all forms of EcMetAP. Regardless of the heterocycle, all the hydroxamic acids are highly potent inhibitors and are selective for the Mn(II) and Fe(II) forms, with IC(50) values between 1 and 2 μM. One indole hydroxamic acid that we previously reported as a potent inhibitor of E. coli peptide deformylase also demonstrated efficiency against EcMetAP. To gain insight into the positioning of the oxazole heterocycle with reversed substitutions at positions 2 and 5, X-ray crystal structures of EcMetAP-Mn complexed with two such oxazole hydroxamic acids were solved. Irrespective of the [metal]/[apo-MetAP] ratio, the active site consistently contains a dinuclear manganese center, with the hydroxamate as bridging ligand. Asp 97, which adopts a bidentate binding mode to the Mn2 site in the holoenzyme, is twisted in both structures toward the hydroxamate bridging ligand to favor the formation of a strong hydrogen bond. Most of the compounds show weak antibacterial activity against a wild-type E. coli strain. However, increased antibacterial activity was observed mainly for compounds with a 2-substituted phenyl group in the presence of the nonapeptide polymyxin B and phenylalanine-arginine-β-naphthylamide as permeabilizer and efflux pump blocker, respectively, which boost the intracellular uptake of the inhibitors.

Active Site Metal Identity Alters Histone Deacetylase 8 Substrate Selectivity: A Potential Novel Regulatory Mechanism

“…42 E. coli methionine aminopeptidase demonstrates metal-dependent inhibitor selectivity (Fe(II), Co(II), and Mn(II)). 43 Klebsiela oxytoce acire-ductone dioxygenase is an example of a known cambialistic enzyme; if Fe(II) is bound it catalyzes one reaction, and if Ni(II) or Co(II) is bound it catalyzes a different chemical reaction. 44 The metal-dependent bacterial deacetylase LpxC from E. coli has been shown to bind either Zn(II) or Fe(II) based on the relative abundance of these metals in the cell.…”

Synthesis and Antibacterial Evaluation of 3,5-Diaryl-1,2,4-oxadiazole Derivatives

“…The compounds were synthesized based on the structural skeleton reported in Table 1, 25,26,39 which has the central 1,2,4-oxadiazole nucleus and phenyl radicals linked at the C-3 and C-5 positions of the heterocycle. Thus, two sets of compounds involving chlorinated and pyridine derivatives were synthesized.…”

Advances in Bacterial Methionine Aminopeptidase Inhibition

“…Additionally, ( 17 ) was screened against Ab MetAPx and Ab MetAPy, with preferential binding again observed for the Mn(II) loaded forms of the enzymes ( Ab MetAPx IC 50 = 13, 394, 188, 358 μM; Mn(II), Co(II), Ni(II) and Fe(II), respectively; Ab MetAPy IC 50 = 0.92, 381, 186, 288; Mn(II), Co(II), Ni(II) and Fe(II), respectively) [21]. Compound ( 17 ) was also screened against Mt MetAP1c and was found to be active against the Mn(II) loaded form of the enzyme only ( Mt MetAP1c IC 50 = 14 μM; Mn(II); IC 50 = >500 μM; Co(II), Ni(II) and Fe(II)) [40] where inhibition of Bp MetAP1 with Co(II) cofactors by ( 17 ) was not observed (IC 50 = >250 μM) [22]. …”

“…coli cells with recombinant Mt MetAP1c [40]. Although the in vitro activity of these compounds against bacterial MetAPs has been established, compound ( 17 ) was ineffective at inhibiting E. coli growth.…”