Redox balance and glutathione metabolism.
Handling reactive oxygen species, detoxification conjugation, and cellular redox state.
Cells continuously generate reactive oxygen species as a by-product of aerobic metabolism, and they maintain an elaborate system to keep those species in check. Glutathione is the centre of that system: a tripeptide of glutamate, cysteine, and glycine, present in millimolar concentrations inside cells, and the largest pool of non-protein thiol in the body. Its reactive cysteine sulfhydryl group is what does the work. Glutathione operates in several ways at once. It neutralises radicals directly, and it serves as the substrate for glutathione peroxidase enzymes that reduce hydrogen peroxide and lipid peroxides to harmless products, becoming oxidised to glutathione disulfide in the process and then being regenerated by glutathione reductase using NADPH. The ratio between reduced and oxidised forms is one of the standard measures of a cell's redox state. Glutathione also regenerates other antioxidants including vitamins C and E, so its depletion degrades the whole antioxidant network rather than just one component. Separately, glutathione S-transferases conjugate it to toxins, drugs, and electrophilic metabolites during phase II detoxification, making them water-soluble for excretion, which is why hepatic glutathione depletion is the central event in certain overdose toxicities. A proposed cosmetic application rests on different chemistry: inhibition of tyrosinase, the rate-limiting enzyme in melanin synthesis, and a shift of pigment production from darker eumelanin toward lighter pheomelanin. A second compound is included here because it addresses oxidative damage at its source rather than downstream. By stabilising the inner mitochondrial membrane and the organisation of the electron transport chain, it is proposed to reduce the leakage of electrons that generates reactive oxygen species in the first place, which is conceptually upstream of scavenging them. The honest complication with glutathione is delivery. Oral glutathione is largely broken down into its constituent amino acids in the gut, and the extent to which any intact molecule reaches cells is a long-standing point of contention. Raising intracellular glutathione by supplying cysteine precursors is a better-established route than supplying the tripeptide itself. Intravenous and injected use for skin lightening has been the subject of regulatory safety warnings in several countries, is not an approved indication, and has been associated with serious adverse events. The underlying biochemistry is textbook; the interventions built on it are not.
Peptides acting through this pathway.
FAQ.
What does redox balance and glutathione metabolism do?
Cells continuously generate reactive oxygen species as a by-product of aerobic metabolism, and they maintain an elaborate system to keep those species in check. Glutathione is the centre of that system: a tripeptide of glutamate, cysteine, and glycine, present in millimolar concentrations inside cells, and the largest pool of non-protein thiol in the body. Its reactive cysteine sulfhydryl group is what does the work. Glutathione operates in several ways at once. It neutralises radicals directly, and it serves as the substrate for glutathione peroxidase enzymes that reduce hydrogen peroxide and lipid peroxides to harmless products, becoming oxidised to glutathione disulfide in the process and then being regenerated by glutathione reductase using NADPH. The ratio between reduced and oxidised forms is one of the standard measures of a cell's redox state. Glutathione also regenerates other antioxidants including vitamins C and E, so its depletion degrades the whole antioxidant network rather than just one component. Separately, glutathione S-transferases conjugate it to toxins, drugs, and electrophilic metabolites during phase II detoxification, making them water-soluble for excretion, which is why hepatic glutathione depletion is the central event in certain overdose toxicities. A proposed cosmetic application rests on different chemistry: inhibition of tyrosinase, the rate-limiting enzyme in melanin synthesis, and a shift of pigment production from darker eumelanin toward lighter pheomelanin. A second compound is included here because it addresses oxidative damage at its source rather than downstream. By stabilising the inner mitochondrial membrane and the organisation of the electron transport chain, it is proposed to reduce the leakage of electrons that generates reactive oxygen species in the first place, which is conceptually upstream of scavenging them. The honest complication with glutathione is delivery. Oral glutathione is largely broken down into its constituent amino acids in the gut, and the extent to which any intact molecule reaches cells is a long-standing point of contention. Raising intracellular glutathione by supplying cysteine precursors is a better-established route than supplying the tripeptide itself. Intravenous and injected use for skin lightening has been the subject of regulatory safety warnings in several countries, is not an approved indication, and has been associated with serious adverse events. The underlying biochemistry is textbook; the interventions built on it are not.
Which peptides act through redox balance and glutathione metabolism?
Glutathione, SS-31. They share this pathway but differ in evidence, approval, and safety.
Does this mechanism prove a peptide works?
No. Mechanistic plausibility is not proof of clinical benefit. A plausible pathway is a reason to study a compound, not evidence that it works in humans.