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

In this work, the effects of I 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 I, especially trypsin. Upon gradual addition of I, the intrinsic fluorescence quenching of trypsin and pepsin were observed by mainly static collision and hydrophobic forces. I 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 I. The synchronous fluorescence spectral results indicated that I 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 I. These investigations may constitute a solid work to further explain the process of migration and transformation of I in digestive system.