Quantum chemistry study on the interaction of the exogenous ligands and the catalytic zinc ion in matrix metalloproteinases

Six zinc complexes, Zn(imidazole)(3)X (where X = water, CH3S-, hydroxamate, formylhydroxylamine, hypophosphite, and acetate), have been calculated with the density functional theory (DFT) method B3LYP/6-31G* to probe the interaction between the exogenous ligands and the catalytic zinc ion in matrix metalloproteinases (MMPs). According to our calculation, their interaction modes can be divided into three classes. The structural features of these complexes are in agreement with the X-ray data in the Cambridge Structural Database and the Protein Data Bank. The atomic charge analyses proved that the catalytic water molecule in the active site of MMPs can be activated after coordinating with the zinc ion and thus acts as a good nucleophile to attack and degrade the substrate of MMPs. The geometric parameters of these complexes, the charge transfers from the exogenous ligands to the Zn(II), and the calculated relative binding, free energy characterize well the binding ability of these ligands with the zinc ion. The inhibitory activities of the MMP inhibitors, which contain the same substituents and different zinc binding groups (ZBGs), correlate well with the binding free energies predicted by the DFT calculation with correlation coefficients of 0.969 for matrilysin and 0.939 for human fibroblast collagenase (HFC). This gives a possible good strategy for predicting the inhibitory activity for the newly designed inhibitors of MMPs; those potential inhibitors that would exhibit strong binding ability of ZBGs to Zn(II) using this paradigm would therefore be expected to have greater inhibitory activity.