In the present study, experimentally observed inhibition mechanism of zinc enzyme carbonic anhydrase XII (CA XII) by new class of suicide inhibitors, glycosyl coumarin, has been modeled using of density functional theory (DFT) to investigte the geometrical parameters and thermocemical aspects of this mechanism in the solution phase. In the first step of this research the most stable conformer of four 7-substituted sugar coumarin including galactose, mannose, ribose and glucose derivatives as

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... e effective and coumarin as the less effective inhibitor of CA XII respectively has been search and interact with CA XII active site. The results of our calculations indicate that all above mentioned inhibitors do not directly interact with the metal ion from the CA active center. Moreover, the calculated thermodynamic function values indicate the presence of sugar moiety in the coumarin molecule was associated with more effective inhibition. Furthermore, interactions between the most stable conformer of galactose derivative as the best inhibitors with CA XII in presence of water solvent were studied by employing explicit solvent model. In addition the good agreements between our calculated results with experimental data indicate a reliable agreement of method of calculations.