Glutathione transferases (GSTs, EC 2.5.1.18) are a widespread family of enzymes that play a central role in the detoxification, metabolism, and transport or sequestration of endogenous or xenobiotic compounds. During the last two decades, delineation of the important structural and catalytic features of GSTs has laid the groundwork for engineering GSTs, involving both rational and random approaches, aiming to create new variants with new or altered properties. These approaches have expanded the usefulness of native GSTs, not only for understanding the fundamentals of molecular detoxification mechanisms, but also for the development medical, analytical, environmental, and agricultural applications. This review article attempts to summarize successful examples and current developments on GST engineering, highlighting in parallel the recent knowledge gained on their phylogenetic relationships, structural/catalytic features, and biotechnological applications.

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The MDR-involved human GSTA1-1, an important isoenzyme overexpressed in several tumors leading to chemotherapeutic-resistant tumour cells, has been targeted by 2,2'-dihydroxybenzophenones and some of their carbonyl N-analogues, as its potential inhibitors. A structure-based library of the latter was built-up by a nucleophilic cleavage of suitably substituted xanthones to 2,2'-dihydroxy-benzophenones (5-9) and subsequent formation of their N-derivatives (oximes 11-13 and N-acyl hydrazones 14-16). Screening against hGSTA1-1 led to benzophenones 6 and 8, and hydrazones 14 and 16, having the highest inhibition potency (IC₅₀ values in the range 0.18 ± 0.02 to 1.77 ± 0.10 μM). Enzyme inhibition kinetics, molecular modeling and docking studies showed that they interact primarily at the CDNB-binding catalytic site of the enzyme. In addition, the results from cytotoxicity studies with human colon adenocarcinoma cells showed low LC₅₀ values for benzophenone 6 and its N-acyl hydrazone analogue 14 (31.4 ± 0.4 μM and 87 ± 1.9 μM, respectively), in addition to the strong enzyme inhibition profile (IC₅₀(6)=1,77 ± 0.10 μM; IC₅₀(14)=0.33 ± 0.05 μM). These structures may serve as leads for the design of new potent mono- and bi-functional inhibitors and pro-drugs against human GTSs.

Mental disorders are neuropsychiatric conditions that are marked by unusual or irregular thinking, feelings, or behavior, and lead to distress and/or impaired functions. Major psychiatric conditions are depression, anxiety, and psychoses of various types. Their etiopathogeneses, of a primary or secondary origin, are associated with genetic and environmental factors. They are commonly treated with psychoactive drugs (also known as psychotropics), which target serotonin, dopamine, norepinephrine, glutamate, and nuclear receptors (NRs), including retinoic acid receptor-related orphan receptors (RORs) and other receptors in the central nervous system (CNS). Herein we present a diverse array of isoxazole derivatives, among which are some prominent marketed drugs. Some of the derivatives and forms, including N-oxides, are under either (pre)clinical evaluation or patent protection as new generation of psychotropics, and a few have effective blood-brain barrier (BBB) permeability. Various drug-like isoxazol(in)es and their structural features and efficiency, modified through scaffold hopping, are described and discussed in the context of treating neuropsychiatric conditions.

The isoenzyme of human glutathione transferase P1-1 (hGSTP1-1) is involved in multi-drug resistance (MDR) mechanisms in numerous cancer cell lines. In the present study, the inhibition potency of two curcuminoids and eleven monocarbonyl curcumin analogues against hGSTP1-1 was investigated. Demethoxycurcumin (Curcumin II) and three of the monocarbonyl curcumin analogues exhibited the highest inhibitory activity towards hGSTP1-1 with IC50 values ranging between 5.45 ± 1.08 and 37.72 ± 1.02 μM. Kinetic inhibition studies of the most potent inhibitors demonstrated that they function as non-competitive/mixed-type inhibitors. These compounds were also evaluated for their toxicity against the prostate cancer cells DU-145. Interestingly, the strongest hGSTP1-1 inhibitor, (DM96), exhibited the highest cytotoxicity with an IC50 of 8.60 ± 1.07 μΜ, while the IC50 values of the rest of the compounds ranged between 44.59–48.52 μΜ. Structural analysis employing molecular docking, molecular dynamics (MD) simulations, and binding-free-energy calculations was performed to study the four most potent curcumin analogues as hGSTP1-1 inhibitors. According to the obtained computational results, DM96 exhibited the lowest binding free energy, which is in agreement with the experimental data. All studied curcumin analogues were found to form hydrophobic interactions with the residue Gln52, as well as hydrogen bonds with the nearby residues Gln65 and Asn67. Additional hydrophobic interactions with the residues Phe9 and Val36 as well as π–π stacking interaction with Phe9 contributed to the superior inhibitory activity of DM96. The van der Waals component through shape complementarity was found to play the most important role in DM96-inhibitory activity. Overall, our results revealed that the monocarbonyl curcumin derivative DM96 acts as a strong hGSTP1-1 inhibitor, exerts high prostate cancer cell cytotoxicity, and may, therefore, be exploited for the suppression and chemosensitization of cancer cells. This study provides new insights into the development of safe and effective GST-targeted cancer chemosensitizers.