Background: The 26kDa glutathione transferase (GST, EC 2.5.1.18) from Schistosoma japonicum (SjGST) is recognized as the major detoxification enzyme of S. japonicum, a pathogenic helminth causing schistosomiasis.

Objective: In the present study, the interaction of the chlorotriazine dye Cibacron blue 3GA (CB3GA) and its structural analogues with SjGST was investigated. The work aimed to shed light on the non-substrate ligand-binding properties of the enzyme.

Methods: Kinetic inhibition analysis, affinity labelling experiments and molecular modelling studies were employed.

Results: The results showed that CB3GA is a potent inhibitor (IC₅₀ 0.057 ± 0.003 μM) towards SjGST. The enzyme was specifically and irreversibly inactivated by the dichlorotriazine-analogue of CB3GA (IC₅₀ 0.190 ± 0.024 μM), following a biphasic pseudo-first-order saturation kinetics with approximately 1 mol of inhibitor per mol of the dimeric enzyme being incorporated. All other monochlorotriazine analogues behave as reversible inhibitors with lower inhibition potency (IC₅₀ 5.2-82.3 μM). Kinetic inhibition studies, together with molecular modelling and molecular dynamics simulations, established that the CB3GA binding site overlaps both the G- and H-sites. Both hydrophobic/ polar interactions, as well as steric effects, have decisive roles in determining the inhibitory strength of CB3GA and its analogues.

Conclusion: The results of the present study might be useful in future drug design and development efforts towards SjGST.

背景：来自日本血吸虫 (SjGST) 的 26kDa 谷胱甘肽转移酶 (GST, EC 2.5.1.18) 被认为是日本血吸虫的主要解毒酶，日本血吸虫是一种引起血吸虫病的病原蠕虫。

目的：在本研究中，研究了氯三嗪染料 Cibacron blue 3GA (CB3GA) 及其结构类似物与 SjGST 的相互作用。这项工作旨在阐明该酶的非底物配体结合特性。

方法：采用动力学抑制分析、亲和标记实验和分子建模研究。

结果：结果表明，CB3GA 是一种针对 SjGST 的有效抑制剂 (IC ₅₀ 0.057 ± 0.003 μM)。该酶被 CB3GA 的二氯三嗪类似物 (IC ₅₀ 0.190 ± 0.024 μM)特异性且不可逆地灭活，遵循双相伪一级饱和动力学，每摩尔二聚酶掺入约 1 摩尔抑制剂。所有其他一氯三嗪类似物均表现为可逆抑制剂，抑制效力较低 (IC ₅₀5.2-82.3 微米）。动力学抑制研究，连同分子建模和分子动力学模拟，确定 CB3GA 结合位点与 G 位点和 H 位点重叠。疏水/极性相互作用以及空间效应在确定 CB3GA 及其类似物的抑制强度方面具有决定性作用。

结论：本研究的结果可能有助于未来针对 SjGST 的药物设计和开发工作。