Evaluation of the binding mechanism of iodine with trypsin and pepsin: A spectroscopic and molecular docking.

In this work, the effects of I2 on the activities and conformational structures of digestive enzymes, trypsin and pepsin were studied. The results indicated that the enzyme activities were decreased to some extent in the presence of I2, especially trypsin. Upon gradual addition of I2, the intrinsic fluorescence quenching of trypsin and pepsin were observed by mainly static collision and hydrophobic forces. I2 is more likely to cause the fluorescence quenching of trypsin than that of pepsin. Compared with pepsin, trypsin has a greater ability to bind with I2. The synchronous fluorescence spectral results indicated that I2 induced the quaternary structure changes of trypsin/pepsin and changed the hydrophobicity of Tyr and Trp residues. In addition, molecular docking was used to obtain the binding mode and the various amino acid residues of trypsin and pepsin with I2. These investigations may constitute a solid work to further explain the process of migration and transformation of I2 in digestive system.