Intrinsic thermodynamics of sulfonamide inhibitor binding to human carbonic anhydrases I and II

Abstract

Human carbonic anhydrase (CA) I and II are cytosolic proteins, where their expression disorders can cause diseases such as glaucoma, edema, epilepsy or cancer. There are numerous inhibitors that target these isozymes, but it is difficult to design compounds that could bind to one of these proteins specifically. The binding of sulfonamide inhibitor to a CA is linked to several protonation reactions, namely, deprotonation of the sulfonamide group, protonation of the active site zinc hydroxide and the compensating protonation–deprotonation of buffer. By performing binding experiments at various pHs and buffers, all those contributions were dissected and the “intrinsic” binding parameters were calculated. Intrinsic thermodynamic binding parameters to CA I and II were determined for such widely studied drugs as acetazolamide, ethoxzolamide, methazolamide, trifluoromethanesulfonamide and dichlorophenamide. The assignment of all contributions should enhance our understanding of the underlying energetics and increase our capability to design more potent and specific CA inhibitors.

• Carbonic anhydrase
• enthalpy
• fluorescent thermal shift assay
• intrinsic parameters
• isothermal titration calorimetry
• ligand binding
• thermal shift assay
• ThermoFluor

Declaration of interest

The authors report no conflict of interest. This research was funded by the European Social Fund under the Global Grant measure (no. VP1-3.1.-SMM-07-K-02-009). Authors thank FP7-REGPOT-2009-1 grant ‘MoBiLi’ agreement No.: 245721 and the COST projects TD0905 and CM0804.