How mutations affecting the ligand-receptor interactions: a combined MD and QM/MM calculation on CYP2E1 and its two mutants

Theoretical Study on the Metabolic Mechanism of Heptachlor in Human Cytochrome P450 Enzymes

Heptachlor (HEP) is an insecticide metabolized by cytochrome P450 (CYP) enzymes in the human liver, resulting in the formation of heptachlor epoxide (HEPX). HEPX can persist in the human body for a long duration. Therefore, it can be extremely harmful. A comprehensive understanding of HEP's metabolic fate may provide a theoretical basis for mitigating associated hazards. However, the specific human CYP isoforms that metabolize HEP, and their metabolic mechanisms, remain unclear. In this study, eight human CYP isoforms were used as catalytic enzymes to investigate the metabolic mechanism of HEP using molecular docking, molecular dynamics simulations, and quantum mechanical calculations. These results indicate that HEP primarily binds to CYP enzymes through hydrophobic interactions, and that the binding positions of HEP are determined by the composition and shape of the hydrophobic pockets near the active site. Based on the reaction distance, CYP2A6, CYP3A4, and CYP3A5 were the only three enzymes that could metabolize HEP. The epoxidation of HEP catalyzed by the doublet state of compound I was effectively concerted, and the rate-determining step was the electrophilic attack of the oxygen atom on HEP. The energy barriers of the rate-determining step vary significantly among different enzymes. A comparison of these energy barriers suggested that CYP3A5 is the most likely enzyme for HEP catalysis in humans.

Assessing the effect of a series of mutations on the dynamic behavior of phosphite dehydrogenase using molecular docking, molecular dynamics and quantum mechanics/molecular mechanics simulations

Discovered in Pseudomonas stutzeri, phosphite dehydrogenase (PTDH) is an enzyme that catalyzes the oxidation of phosphite to phosphate while simultaneously reducing NAD⁺ to NADH. Despite several investigations into the mechanism of reaction and cofactor regeneration, only a few studies have focused on improving the activity and stability of PTDH. In this study, we combine molecular docking, molecular dynamics (MD) simulation, and Quantum Mechanics/Molecular Mechanics (QM/MM) to identify the impact of 30 mutations on the activity and stability of PTDH. Molecular docking results suggest that E266Q, K76A, K76M, K76R, K76C, and R237K can act on the NAD⁺ binding site through relatively weak bond development due to their high free binding energy. Moreover, Mulliken population analysis and potential energy barrier indicate that T101A, E175A, E175A/A176R, A176R, and E266Q act on phosphite oxidation. The mutants M53N, M53A, K76R, D79N, D79A, T101A, W134A, W134F Y139F, A146S, E175A, F198I, F198M, E266Q, H292K, S295A, R301K, and R301A were found to act on the structural dynamic of PTDH. The remaining mutants cause the loss of the nitrogen atom of R237 and H292, respectively, inactivating the enzyme. This study provides specific explanations of how mutations affect weak interactions of PTDH. The results should allow researchers to conduct experimental studies to improve PTDH activity and stability.Communicated by Ramaswamy H. Sarma.

Functional and binding studies of gallic acid showing platelet aggregation inhibitory effect as a thrombin inhibitor

Objective

This study was devoted to identifying natural thrombin inhibitors from traditional Chinese medicine (TCM) and evaluating its biological activity in vitro and binding characteristics.

Methods

A combination strategy containing molecular docking, thrombin inhibition assay, surface plasmon resonance (SPR) and molecular dynamics simulation were applied to verify the study result.

Results

Gallic acid was confirmed as a direct thrombin inhibitor with IC50 of 9.07 μmol/L and showed a significant inhibitory effect on thrombin induced platelet aggregation. SPR-based binding studies demonstrated that gallic acid interacted with thrombin with a KD value of 8.29 μmol/L. Molecular dynamics and binding free energy analysis revealed that thrombin-gallic acid system attained equilibrium rapidly with very low fluctuations, the calculated binding free energies was -14.61 kcal/mol. Ala230, Glu232, Ser235, Gly258 and Gly260 were the main amino acid residues responsible for thrombin inhibition by gallic acid, providing a mechanistic basis for further optimization.

Conclusion

This study proved that gallic acid is a direct thrombin inhibitor with platelet aggregation inhibitory effect, which could provide a basis for the follow-up research and development for novel thrombin inhibitors.

Discovery of natural 15-LOX small molecule inhibitors from Chinese herbal medicine using virtual Screening, biological evaluation and molecular dynamics studies

Chinese herbal medicines (CHM) are frequently used to treat different types of inflammatory diseases and 15-Lipoxygenase (15-LOX) is a critical target enzyme for treating various inflammatory diseases. In this study, natural 15-LOX inhibitors were identified in CHM using an approach of virtual screening combined with the biological assays. First, an in-house Chinese medicine database containing 360 compounds was screened using a virtual screening approach based on pharmacophore and molecular docking to uncover several novel potential 15-LOX inhibitors. Secondly, the inhibitory effect of virtual screening hits against the 15-LOX enzyme was validated in an in vitro enzyme inhibition assay. Then, a tumor necrosis factor-α (TNF-α) release assay was carried out to explore the anti-inflammatory response of the active compounds. Furthermore, molecular dynamics (MD) simulation and binding free energy calculation were applied to analyze the process of inhibitors binding and also compared the mode of binding of the inhibitors by using the Molecular Mechanics-Generalized Born Surface Area (MM/GBSA) method. Finally, licochalcone B and eriodictyol were confirmed as inhibitors of the 15-LOX enzyme with IC₅₀ values of 9.67 and 18.99 μM, respectively. In vitro cell-based assay showed that licochalcone B and eriodictyol inhibited the release of TNF-α factor in RAW264.7 cells stimulated by lipopolysaccharides (LPS) in a dose-dependent manner. Molecular dynamics and binding free energy analysis showed that the two 15-LOX-ligand systems immediately attained equilibrium with almost 1 Å fluctuation, the calculated binding free energies were found around -18.89 and -12.96 kcal/mol for licochalcone B and eriodictyol, respectively. Thr412, Arg415, Val420, Thr429, Ile602 and Trp606 were the main amino acid residues for the inhibition of 15-LOX enzyme activity. The current study confirms that licochalcone B and eriodictyol are 15-LOX inhibitors and can suppress the release of the TNF-α factor in RAW264.7 cells stimulated by LPS, thus providing a basis for the follow-up research and development for 15-LOX inhibitors.

Molecular dynamics simulation reveals how phosphorylation of tyrosine 26 of phosphoglycerate mutase 1 upregulates glycolysis and promotes tumor growth

Phosphoglycerate mutase 1 (PGAM1) catalyzes the eighth step of glycolysis and is often found upregulated in cancer cells. To test the hypothesis that the phosphorylation of tyrosine 26 residue of PGAM1 greatly enhances its activity, we performed both conventional and steered molecular dynamics simulations on the binding and unbinding of PGAM1 to its substrates, with tyrosine 26 either phosphorylated or not. We analyzed the simulated data in terms of structural stability, hydrogen bond formation, binding free energy, etc. We found that tyrosine 26 phosphorylation enhances the binding of PGAM1 to its substrates through generating electrostatic environment and structural features that are advantageous to the binding. Our results may provide valuable insights into computer-aided design of drugs that specifically target cancer cells with PGAM1 tyrosine 26 phosphorylated.