## 3 Results
### Molecular Docking Study
As is well known, Arg522 is considered as an important ligand to the second Cl\({}^{-}\) of the ACE. Therefore, the high ACE inhibitory effect of LPSW may be caused by Arg522 and interaction bonds, such as H-bonds and pi-pi interactions. The CDocker energy of LPSW was \(-\)55.1801 kJ/mol (Figure 4D; Tables 3-5). The CDocker energy of LP was 53.3389 kJ/mol. In this case, LP bound to the ACE receptor via the second binding position that contained Glu411, Ala356, and Trp357. Hydrogen and pi-pi bonds were identified in this LP-ACE complex, including three H-bonds with the residue Glu411 (3.0 A), Ala356 (1.7 A; 1.9 A), and one \(\pi\)-\(\pi\) interaction with Trp357 (4.9 A). The expression of Glu411 bound to a zinc ion may play a role in improving the ACE inhibitory activity (Figure 4E; Tables 3-5). The dipeptide SW can bind to the S1 pocket of the ACE receptor at Glu384, Ala354, and Tyr523 and the S2 pocket at His353. Furthermore, docking also occurred with different residues, including His387, Arg522, and His410. The interaction between SW and the ACE receptor involved the formation of four \(\pi\)-\(\pi\) bonds at His387 (4.4 A; 5.4 A) and His410 (4.2 A; 4.7 A) and six H-bonds, including Glu384 (3.7 A), Ala354 (1.9 A), Tyr523 (2.2A), His353 (2.2 A) and Arg522 (2.1 A; 2.5 A) (Figure 4F; Tables 3-5). The CDocker energy of SW was \(-\)61.9276 kJ/mol. The appearance of Arg522 (a notable ligand to the second Cl- of the ACE) and the active sites at both pockets 1 and 2 may significantly contribute to enhancing the ACE inhibitory activity of SW (Figure 4F; Tables 3-5). The CDocker energy of SW was \(-\)61.9276 kJ/mol. According to our docking results (Tables 3 and 5), the binding interaction of \(\pi\)-\(\pi\) may also play an important role in contributing to the structural stability of the ACE-peptide complex, leading to the strong inhibition of ACE by peptides. [PERSON] et al. found similar results to ours and concluded that the high ACE inhibitory effect of hazelnut peptides (AVKVL, YLVR, and TLVGR) is not only determined by hydrogen and electrostatic bonds, but that the \(\pi\)-\(\pi\) interactions also offer a significant contribution [46]. Based on the kinetic and docking results, it can be concluded that WLQL acts as a competitive inhibitor and can interact with the active sites of ACE receptors. Interestingly, the peptide LPSW was determined as a non-competitive inhibitor via kinetic analysis. In this way, this peptide can only bind to non-active sites and this was confirmed through molecular docking. However, LPSW was cleavaged after being pre-incubated with ACE, and then small fragments (LP and SW) were also identified via LC-MS analysis. Therefore, the mechanism of LPSW must be studied more deeply to clearly understand this inconsistency. Docking simulation is considered as an efficient method to predict the biological properties of peptides through the analysis of specific binding interactions formed between peptides and proteins. However, the determination of the characteristics of bioactive peptides in silico does not provide enough evidence to be conclusive; therefore, a corresponding in vitro assay must be performed for the predicted peptides [25; 47].