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Inhibition of Cysteine Proteases by 6,6'-Dihydroxythiobinupharidine (DTBN) from Nuphar lutea.

ABSTRACT: The specificity of inhibition by 6,6'-dihydroxythiobinupharidine (DTBN) on cysteine proteases was demonstrated in this work. There were differences in the extent of inhibition, reflecting active site structural-steric and biochemical differences. Cathepsin S (IC₅₀ = 3.2 μM) was most sensitive to inhibition by DTBN compared to Cathepsin B, L and papain (IC₅₀ = 1359.4, 13.2 and 70.4 μM respectively). DTBN is inactive for the inhibition of M^pro of SARS-CoV-2. Docking simulations suggested a mechanism of interaction that was further supported by the biochemical results. In the docking results, it was shown that the cysteine sulphur of Cathepsin S, L and B was in close proximity to the DTBN thiaspirane ring, potentially forming the necessary conditions for a nucleophilic attack to form a disulfide bond. Covalent docking and molecular dynamic simulations were performed to validate disulfide bond formation and to determine the stability of Cathepsins-DTBN complexes, respectively. The lack of reactivity of DTBN against SARS-CoV-2 M^pro was attributed to a mismatch of the binding conformation of DTBN to the catalytic binding site of M^pro. Thus, gradations in reactivity among the tested Cathepsins may be conducive for a mechanism-based search for derivatives of nupharidine against COVID-19. This could be an alternative strategy to the large-scale screening of electrophilic inhibitors.

SUBMITTER: Waidha K

PROVIDER: S-EPMC8399019 | biostudies-literature |

REPOSITORIES: biostudies-literature

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6,6'-Dihydroxythiobinupharidine (DTBN) Purified from <i>Nuphar lutea</i> Leaves Is an Inhibitor of Protein Kinase C Catalytic Activity.

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Relationships between key functional traits of the waterlily Nuphar lutea and wetland nutrient content.

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