Overlooked and misunderstood: can glutathione conjugates be clues to understanding plant glutathione transferases?

24-epibrassinolide promotes resilience against arsenic stress via modulating amino acid profiles and mRNA abundance of CYP450 and MRP genes in Zea mays L

This study investigates the role of 24-epibrassinolide (BR, 10-2 μM) in mitigating arsenic (As)-induced stress in maize (Zea mays L. cv. 704). Seedlings were exposed to As at concentrations of 0, 5, 10, 25, 50, 100, and 250 μM, with or without BR application. Arsenic exposure increased oxidative damage markers such as MDA and H₂O₂ while BR treatment significantly enhanced antioxidant enzymes activities including ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), glutathione reductase (GR) and glutathione S-transferase (GST), reducing reactive oxygen species (ROS) levels, and minimizing oxidative damage. Additionally, BR significantly increased proline, phenolic compounds, flavonoids, and soluble sugars, contributing to osmoprotection and stress tolerance, as well as enhancing FRAP and DPPH antioxidant activities. Furthermore, BR increased amino acids (AAs) such as proline (Pro), cysteine (Cys), glutamine (Gln), and glutamate (Glu). Gene expression analysis revealed significant upregulation of detoxification-related genes including cytochrome P450 monooxygenases (CYPs), GT1, GST27 and multidrug resistance-associated proteins (MRPs) under BR treatment. These findings suggest that BR enhances maize tolerance to As toxicity by activating detoxification pathways, improving antioxidant defense, and stabilizing metabolic processes. The results underscore the potential application of BR in sustainable agriculture to improve crop resilience in As-contaminated soils.

Current and future perspectives for enhancing our understanding of the evolution of plant metabolism

The special issue 'The evolution of plant metabolism' has brought together original research, reviews and opinions that cover various aspects from the full breath of plant metabolism including its interaction with the environment including other species. Here, we briefly summarize these efforts and attempts to extract a consensus opinion of the best manner in which to tackle this subject both now and in the future. This article is part of the theme issue 'The evolution of plant metabolism'.

Mutations Selectively Evolving Peroxidase Activity Among Alternative Catalytic Functions of Human Glutathione Transferase P1-1

Glutathione transferases are detoxication enzymes with broad catalytic diversity, and small alterations to the protein's primary structure can have considerable effects on the enzyme's substrate selectivity profile. We demonstrate that two point mutations in glutathione transferase P1-1 suffice to generate 20-fold enhanced non-selenium-dependent peroxidase activity indicating a facile evolutionary trajectory. Designed mutant libraries of the enzyme were screened for catalytic activities with alternative substrates representing four divergent chemistries. The chemical reactions comprised aromatic substitution, Michael addition, thiocarbamoylation, and hydroperoxide reduction. Two mutants, R1 (Y109H) and an R1-based mutant V2 (Q40M-E41Q-A46S-Y109H-V200L), were discovered with 16.3- and 30-foldincreased peroxidase activity with cumene hydroperoxide (CuOOH) compared to the wildtype enzyme, respectively. The basis of the improved peroxidase activity of the mutant V2 was elucidated by constructing double-point mutants. The mutants V501 (Q40M-Y109H) and V503 (E41Q-Y109H) were found to have 20- and 21-fold improvements in peroxidase activity relative to the wildtype enzyme, respectively. The steady-state kinetic profiles of mutants R1 and V2 in the reduction of CuOOH were compared to the wildtype parameters. The kcat values for R1 and V2 were 34- and 57-fold higher, respectively, than that of the wildtype enzyme, whereas the mutant Km values were increased approximately 3-fold. A 10-fold increased catalytic efficiency (kcat/Km) in CuOOH reduction is accomplished by the Tyr109His point mutation in R1. The 23-fold increase of the efficiency obtained in V2 was caused by adding further mutations primarily enhancing kcat. In all mutants with elevated peroxidase activity, His109 played a pivotal role.