Köksal, Muhammed MuratŞekerler, TurgutŞener, Azize YamanTemel Eczacılık Bilimleri Bölümü2025-08-102025-08-1020252630-634410.12991/jrespharm.16262212-s2.0-105012428466https://doi.org/10.12991/jrespharm.1626221Protein disulfide isomerase (PDI), a multifunctional protein plays an important role as oxidoreductase, isomerase and chaperone in the cell. Prior studies have identified PDI is highly expressed in many different cancer types and presented as a new potential target for cancer treatment. Here, we investigated vitamin D and its analogue paricalcitol in silico interaction of the human PDI and inhibition of PDI reductase activity in vitro. We observed a non-covalent mechanism where the main skeleton of the vitamin D3 and paricalcitol structure is located at the hydrophobic site in the b' domain of PDI and forms a hydrogen bond with a residue (Hisl38) in this domain. They also form multiple weak hydrophobic interactions with various chemical groups of the b' subunit. For the first time, we demonstrate that 1,25-dihydroxyvitamin D3 (1a,25(OH)2 vitamin D3) and paricalcitol inhibit the PDIreductase activity in vitro and their 1C50 values are 20.7911.43 nmol/L and 32.8213.15 nmol/L respectively. The two compounds can also block the denitrosation activity of PDI. © 2025 Elsevier B.V., All rights reserved.eninfo:eu-repo/semantics/openAccessActivity of EnzymesMolecular DockingParicalcitolProtein Disulfide IsomeraseVitamin D3Amino AcidColecalciferolEstradiolHydrogenParicalcitolProtein Disulfide IsomeraseAmino AcidColecalciferolEstradiolHydrogenJuniferdinParicalcitolProtein Disulfide IsomeraseProtein Disulfide Isomerase ReductaseUnclassified DrugArticleChemical ReactionControlled StudyDenitrosationDrug EffectEnzyme ActivityHydrogen BondHydrophobicityIn Silico DesignIn Vitro StudyMolecular DockingProtein ExpressionProtein Protein InteractionProtein StructureArticle