Institute for Research in Molecular Medicine, Universiti Sains Malaysia, Gelugor 11800, Malaysia.
Faculty of Science and Natural Resources, Universiti Malaysia Sabah, Kota Kinabalu 88400, Malaysia.
Molecules. 2022 Mar 31;27(7):2292. doi: 10.3390/molecules27072292.
Dibutyl phthalate (DBP) produced by sp. H11809 exerted inhibitory activity against human GSK-3β ( GSK-3β) and 3D7 ( 3D7) malaria parasites. The current study aimed to determine DBP's plausible mode of action against GSK-3β and 3D7. Molecular docking analysis indicated that DBP has a higher binding affinity to the substrate-binding site (pocket 2; -6.9 kcal/mol) than the ATP-binding site (pocket 1; -6.1 kcal/mol) of GSK-3β. It was suggested that the esters of DBP play a pivotal role in the inhibition of GSK-3β through the formation of hydrogen bonds with Arg96/Glu97 amino acid residues in pocket 2. Subsequently, an in vitro GSK-3β enzymatic assay revealed that DBP inhibits the activity of GSK-3β via mixed inhibition inhibitory mechanisms, with a moderate IC of 2.0 µM. Furthermore, the decrease in K value with an increasing DBP concentration suggested that DBP favors binding on free GSK-3β over its substrate-bound state. However, the antimalarial mode of action of DBP remains unknown since the generation of a 3D7 DBP-resistant clone was not successful. Thus, the molecular target of DBP might be indispensable for survival. We also identified nocardamine as another active compound from sp. H11809 chloroform extract. It showed potent antimalarial activity with an IC of 1.5 μM, which is ~10-fold more potent than DBP, but with no effect on GSK-3β. The addition of ≥12.5 µM ferric ions into the culture reduced nocardamine antimalarial activity by 90% under in vitro settings. Hence, the iron-chelating ability of nocardamine was shown to starve the parasites from their iron source, eventually inhibiting their growth.
邻苯二甲酸二丁酯（DBP）由 sp. H11809 产生，对人 GSK-3β（GSK-3β）和 3D7（3D7）疟原虫具有抑制活性。本研究旨在确定 DBP 对 GSK-3β 和 3D7 的可能作用模式。分子对接分析表明，DBP 与 GSK-3β 的底物结合位点（口袋 2；-6.9 kcal/mol）的结合亲和力高于其 ATP 结合位点（口袋 1；-6.1 kcal/mol）。据推测，DBP 的酯通过与口袋 2 中 Arg96/Glu97 氨基酸残基形成氢键，在抑制 GSK-3β 中发挥关键作用。随后，体外 GSK-3β 酶测定表明，DBP 通过混合抑制抑制机制抑制 GSK-3β 的活性，IC 为 2.0 µM。此外，随着 DBP 浓度的增加，K 值的降低表明 DBP 有利于与游离 GSK-3β 结合，而不是与其底物结合的状态。然而，由于未能生成 3D7 DBP 抗性克隆，DBP 的抗疟作用模式仍不清楚。因此，DBP 的分子靶标可能对生存至关重要。我们还从 sp. H11809 氯仿提取物中鉴定出诺卡胺作为另一种活性化合物。它表现出很强的抗疟活性，IC 为 1.5 μM，比 DBP 强 10 倍，但对 GSK-3β 没有影响。在体外环境下，将≥12.5 µM 铁离子加入培养物中，可使诺卡胺的抗疟活性降低 90%。因此，诺卡胺的铁螯合能力使寄生虫无法从其铁源中获取营养，从而最终抑制其生长。
