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A bioinorganic approach to matrix metalloproteinase inhibition

  • Author(s): Puerta, David Thomas
  • et al.
Abstract

In an effort to develop potent inhibitors of matrix metalloproteinases (MMPs), a bioinorganic approach was employed. The synthesis of [(TpPh,Me)Zn(OH)] provided for a structural analogue of the zinc-(tris-histidine) catalytic site of MMPs. The model complex was used to gain insight into the discrepancy of MMP inhibitor (MPI) potencies between mercapto alcohols and mercapto ketones. This initial experiment validated the use of the inorganic model complex as a structural model of the MMP catalytic site. Novel ZBGs for incorporation into MPIs were identified. These ZBGs were complexed with [(TpPh, Me)Zn(OH)] to obtain structural information such as binding mode, bond lengths, and coordination geometry. All ZBG examined were found to bind the model complex in a bidentate fashion, indicating promise for incorporation into a full length MPI. The inhibitory ability of the novel ZBGs was examined in both fluorescent and colorimetric assays using either the catalytic domain of MMPs or native enzyme expressed in a cell culture of neonatal rat ventricular fibroblasts. All novel ZBGs examined were found to be better inhibitors of MMPs in vitro and in cell culture assays than acetohydroxamic acid (the representative ZBG used in the majority of MPIs to date). In order to design full-length MPIs, a combined computational-bioinorganic method was developed. Using the structural coordinates from the [(TpPh,Me)Zn(ZBG)] complexes, the novel ZBGs were modeled into an X-ray crystal structure of uninhibited MMP-3. This study allowed for the examination of the ZBGs in the active site of an MMP. The novel ZBGs were found to have orientations in the active site of MMP-3 amendable to the attachment of a peptidomimetic backbone, necessary for a full-length MPI. Finally, the first MPIs based on the heterocyclic ZBGs were developed. The combined computational-bioinorganic method was augmented with the drug discovery program LUDI. Using LUDI enhanced with structural coordinates from [(TpPh,Me)Zn(3-hydroxy-2-methyl-4-pyrone)], several MPIs were designed. The potential inhibitors were synthesized and were examined in a fluorescence-based assay of MMP-1, -2, and -3. The pyrone-based MPIs were found to be more potent than their hydroxamate analogues, demonstrating the efficacy of a bioinorganic approach to the development of metalloprotein inhibitors

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