glutathionins

Glutathionins are a class of small, thiol-containing peptides found in many organisms. They are characterized by the presence of a gamma-glutamylcysteine moiety, which is crucial for their biological activity. The most well-known member of this group is glutathione (GSH), a tripeptide composed of glutamic acid, cysteine, and glycine. However, the term "glutathionin" can also encompass related molecules with structural variations.

These peptides play vital roles in cellular defense mechanisms. Their primary function is as antioxidants, where they directly scavenge reactive oxygen species (ROS) and reactive nitrogen species (RNS), thereby protecting cells from oxidative damage. Glutathionins are also integral components of the glutathione system, which involves enzymes like glutathione S-transferases (GSTs) and glutathione peroxidases (GPxs). GSTs catalyze the conjugation of glutathione to various electrophilic substrates, aiding in their detoxification and excretion. GPxs utilize glutathione to reduce hydrogen peroxide and lipid hydroperoxides, further contributing to oxidative stress management.

Beyond their antioxidant and detoxification roles, glutathionins are involved in regulating various cellular processes, including cell proliferation, apoptosis, immune response, and DNA synthesis. Their availability and redox status are tightly controlled within cells, reflecting their importance in maintaining cellular homeostasis. The biosynthesis of glutathione begins with the enzymes glutamate-cysteine ligase (GCL) and glutathione synthetase (GS), which sequentially add cysteine and glycine to glutamate.