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| Effect of Different pH on Papain Activity and Its Molecular Mechanism |
| DAI Wen, HUANG Yechuan, HAN Jiayu, HU Xiao, LI Diandian, GUAN Sitong |
| College of Food and Biology, Jingchu University of Technology, Jingmen 448000, China |
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Abstract In order to investigate the impact of different pH levels on papain activity and its molecular mechanism, molecular simulation and fluorescence spectroscopy were employed to analyze the enzyme activity, root mean square error (RMSE), root mean square fluctuation (RMSF), radius of gyration (Rg), inter-protein hydrogen bonding, protein secondary structure, and solvent accessible surface area at various pH values (4, 5, 6, 7, and 8). The results revealed that papain activity was highest at pH 7 and decreased by approximately 5.00% at pH 4 and 5.35% at pH 8 compared to pH 7, respectively. Molecular simulation results indicated that the Rg of papain exhibited minimal fluctuations across different pH levels; RMSD fluctuated greatly at pH 8, and three amino acid residues in the active center displayed significant fluctuations at both pH 4 and pH 8. As the pH value increased gradually, the number of hydrogen bonds in papain also increased except for a decrease by 3.4 at pH 8 compared to pH 7. Under a neutral condition (pH 7), the active center of papain tightly bound to its substrate with a denser internal protein structure; whereas under acidic conditions (pH 4), there was a larger gap between protease’s active center and its substrate binding site along with a looser internal protein structure. The decline in the activity observed at low pH (pH 4) and high pH (pH 8) could be attributed to structural changes protease such as disruption of hydrogen bonds, fluctuations in active center residues, alterations in hydrophobic surface area, and modifications in secondary structures such as β-sheet. This study clarified the effect of pH on papain activity from a molecular simulation perspective.
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YAO Meijie, QI Jiajing, YANG Xiaoyin, MAO Yanwei, XU Baochen, HAO Jiangang, GU Yue, ZHANG Yimin, LIANG Rongrong. Effect of Different pH on the Structure and Thermal Stability of Myoglobin[J]. Meat Research, 2024, 38(6): 1-8. |
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2024, Vol. 38 
