Effects of acetazolamide on the conformations and activities of digestive enzymes: pepsin and trypsin

The changes in activities and conformations of pepsin and trypsin induced by acetazolamide (ACZ) were studied with spectroscopic methods under their respective physiological pH conditions in vitro. The results showed that both the enzymes activities were obviously inhibited as increasing in acetazolamide concentration, while the inhibitory ratio of trypsin was higher than pepsin. The intrinsic fluorescence of the two enzymes was quenched by acetazolamide through static process. Acetazolamide bound trypsin in a more firmly way than pepsin. Thermodynamic analysis revealed that driving force of acetazolamide-pepsin was different from acetazolamide-trypsin. The electrostatic interaction had a significant effect on the binding process of acetazolamide-trypsin, whereas interaction of the acetazolamide-pepsin was driven by hydrogen bonding and van der Waals force. Circular dichroism spectroscopy and synchronous fluorescence showed acetazolamide induced conformational and microenvironmental changes of both the enzymes. These investigations suggested that acetazolamide at different physiological pH may have different effects on the conformations and functions of proteins through variant mechanisms. This study is helpful for understanding the changes in the function and structure of digestive enzymes influenced by acetazolamide in gastrointestinal tract in vivo.