A Potential Peptide From Soy Cheese Produced Using Lactobacillus delbrueckii WS4 for Effective Inhibition of SARS-CoV-2 Main Protease and S1 Glycoprotein

The COVID-19 pandemic caused by novel SARS-CoV-2 has resulted in an unprecedented loss of lives and economy around the world. In this study, search for potential inhibitors against two of the best characterized SARS-CoV-2 drug targets: S1 glycoprotein receptor-binding domain (RBD) and main protease (3CLPro), was carried out using the soy cheese peptides. A total of 1,420 peptides identified from the cheese peptidome produced using Lactobacillus delbrueckii WS4 were screened for antiviral activity by employing the web tools, AVPpred, and meta-iAVP. Molecular docking studies of the selected peptides revealed one potential peptide “KFVPKQPNMIL” that demonstrated strong affinity toward significant amino acid residues responsible for the host cell entry (RBD) and multiplication (3CLpro) of SARS-CoV-2. The peptide was also assessed for its ability to interact with the critical residues of S1 RBD and 3CLpro of other β-coronaviruses. High binding affinity was observed toward critical amino acids of both the targeted proteins in SARS-CoV, MERS-CoV, and HCoV-HKU1. The binding energy of KFVPKQPNMIL against RBD and 3CLpro of the four viruses ranged from −8.45 to −26.8 kcal/mol and −15.22 to −22.85 kcal/mol, respectively. The findings conclude that cheese, produced by using Lb. delbrueckii WS4, could be explored as a prophylactic food for SARS-CoV-2 and related viruses. In addition, the multi-target inhibitor peptide, which effectively inhibited both the viral proteins, could further be used as a terminus a quo for the in vitro and in vivo function against SARS-CoV-2.

Application of the UHPLC-DIA-HRMS Method for Determination of Cheese Peptides

Until now, cheese peptidomics approaches have been criticised for their lower throughput. Namely, analytical gradients that are most commonly used for mass spectrometric detection are usually over 60 or even 120 min. We developed a cheese peptide mapping method using nano ultra-high-performance chromatography data-independent acquisition high-resolution mass spectrometry (nanoUHPLC-DIA-HRMS) with a chromatographic gradient of 40 min. The 40 min gradient did not show any sign of compromise in milk protein coverage compared to 60 and 120 min methods, providing the next step towards achieving higher-throughput analysis. Top 150 most abundant peptides passing selection criteria across all samples were cross-referenced with work from other publications and a good correlation between the results was found. To achieve even faster sample turnaround enhanced DIA methods should be considered for future peptidomics applications.

A scheme for the partial fractionation of cheese peptides

Although proteolysis is regarded as the most important biochemical event in the ripening of most cheese varieties (Rank et al. 1985; Grappin et al. 1985; Law, 1987), current methods for the fractionation of cheese N, yield very heterogeneous fractions (Rank el al. 1985; Grappin et al. 1985; Fox, 1989). This communication describes the results to date of a study undertaken to develop a comprehensive scheme for the fractionation of cheese N.