Single-molecule enzymatic reaction dynamics and mechanisms of GPX3 and TRXh9 from Arabidopsis thaliana

In-depth analysis of the xanthine oxidase inhibitors of Cicer arietinum L.-based receptor-ligand affinity coupled with complex chromatography

INTRODUCTION

Cicer arietinum L. is the choice of health food for people with diabetes, hypertension, and hyperlipidemia. As an essential source of high-nutrition legumes, it is also an important source of dietary isoflavones.

OBJECTIVES

In order to improve the preparation efficiency of natural plants, a rapid biological activity screening and preparation of xanthine oxidase inhibitors from C. arietinum L. was established.

METHODS

Xanthine oxidase (XOD) inhibitors were rapidly screened using ultrafiltration liquid chromatography-mass spectrometry (UF-LC-MS) based on receptor-ligand affinity. The change in XOD activity was evaluated by enzymatic reaction kinetics measurement. The potential bioactive compounds were verified through molecular docking. In addition, the biological activity of ligands screened was separated and purified by complex chromatography. The structures of the compounds were identified by nuclear magnetic resonance spectroscopy.

RESULTS

Three active ingredients, namely daidzin, daidzein, calycosin with XOD binding affinities were identified and isolated from the raw plant materials via semi-preparative high-performance liquid chromatography (HPLC), 0-60 min, 5-50% B and countercurrent chromatography (CCC) (ethyl acetate/acetic acid/water [5:0.8:10, v/v/v]).

CONCLUSION

This study will help to elucidate the mechanisms of action of natural plants of interest at the molecular level and could also provide more opportunities for the discovery and development of new nutritional value from other natural resources.

Plant thiol peroxidases as redox sensors and signal transducers in abiotic stress acclimation

The temporal and spatial patterns of reactive oxygen species (ROS) in cells and tissues decisively determine the plant acclimation response to diverse abiotic and biotic stresses. Recent progress in developing dynamic cell imaging probes provides kinetic information on changes in parameters like H₂O₂, glutathione (GSH/GSSG) and NAD(P)H/NAD(P)⁺, that play a crucial role in tuning the cellular redox state. Central to redox-based regulation is the thiol-redox regulatory network of the cell that integrates reductive information from metabolism and oxidative ROS signals. Sensitive proteomics allow for monitoring changes in redox-related posttranslational modifications. Thiol peroxidases act as sensitive peroxide and redox sensors and play a central role in this signal transduction process. Peroxiredoxins (PRX) and glutathione peroxidases (GPX) are the two main thiol peroxidases and their function in ROS sensing and redox signaling in plants is emerging at present and summarized in this review. Depending on their redox state, PRXs and GPXs act as redox-dependent binding partners, direct oxidants of target proteins and oxidants of thiol redox transmitters that in turn oxidize target proteins. With their versatile functions, the multiple isoforms of plant thiol peroxidases play a central role in plant stress acclimation, e.g. to high light or osmotic stress, but also in ROS-mediated immunity and development.

Focus on Nitric Oxide Homeostasis: Direct and Indirect Enzymatic Regulation of Protein Denitrosation Reactions in Plants

Protein cysteines (Cys) undergo a multitude of different reactive oxygen species (ROS), reactive sulfur species (RSS), and/or reactive nitrogen species (RNS)-derived modifications. S-nitrosation (also referred to as nitrosylation), the addition of a nitric oxide (NO) group to reactive Cys thiols, can alter protein stability and activity and can result in changes of protein subcellular localization. Although it is clear that this nitrosative posttranslational modification (PTM) regulates multiple signal transduction pathways in plants, the enzymatic systems that catalyze the reverse S-denitrosation reaction are poorly understood. This review provides an overview of the biochemistry and regulation of nitro-oxidative modifications of protein Cys residues with a focus on NO production and S-nitrosation. In addition, the importance and recent advances in defining enzymatic systems proposed to be involved in regulating S-denitrosation are addressed, specifically cytosolic thioredoxins (TRX) and the newly identified aldo-keto reductases (AKR).