Structural changes in trypsin induced by the bile salts: An effect of amphiphile hydrophobicity

The present study reports the multi-technique results of the interaction of a series of bile salts, sodium cholate (NaC), sodium taurocholate (NaTC), sodium deoxycholate (NaDC), and sodium taurodeoxycholate (NaTDC) with trypsin under the experimental conditions of 25 degrees C and pH 7.0. The interactions between trypsin and the bile salts were characterized by the surface tension measurements and various spectroscopic techniques like UV-Visible absorption, steady-state fluorescence, and circular dichroism. The results of surface tension measure-ments reveal a strong interaction of trypsin (50 mu M) with the increasing concentration of bile salts, being higher with the bile salt of greater hydrophobicity. The critical aggregation concentration of bile salts in the presence of trypsin (C-1) showed that the bile salts interact strongly with the trypsin in the order of NaTDC > NaDC > NaTC > NaC. UV-visible, steady-state fluorescence, and circular dichroism spectroscopic results confirmed significant unfolding of trypsin due to its interaction with the bile salts, the extent of which followed the same sequence as observed in the surface tension results. It could be concluded that the hydrophobic bile salts that show lower C-1 values and have less delocalized charge, are more effective in unfolding the trypsin. The study would help understand the hydrophobicity-driven unfolding of proteins aided by biological surfactants like bile salts and help devise efficient proteolytic enzyme-based detergent formulations and understand the role of such amphiphiles as antimicrobial agents. (C) 2021 Published by Elsevier B.V.

Automated summary

In this study, the interactions between a series of bile salts and trypsin were investigated using multiple techniques. The results showed that bile salts with higher hydrophobicity had stronger interactions with trypsin, leading to significant unfolding of the protein. The findings contribute to a better understanding of hydrophobicity-driven unfolding of proteins aided by biological surfactants like bile salts.