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

In this work, the effects of I 2 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 2 , especially trypsin. Upon gradual addition of I 2 , the intrinsic fluorescence quenching of trypsin and pepsin were observed by mainly static collision and hydrophobic forces . I 2 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 2 . The synchronous fluorescence spectral results indicated that I 2 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 2 . These investigations may constitute a solid work to further explain the process of migration and transformation of I 2 in digestive system.