Glutathione (GSH) is an important antioxidant in plants, animals, fungi, and some bacteria and archaea. Glutathione is capable of preventing damage to important cellular components caused by reactive oxygen species such as free radicals, peroxides, lipid peroxides, and heavy metals. It is a tripeptide with a gamma peptide linkage between the carboxyl group of the glutamate side chain and the amine group of cysteine, and the carboxyl group of cysteine is attached by normal peptide linkage to a glycine.

Thiol groups are reducing agents, existing at a concentration around 5 mM in animal cells. Glutathione reduces disulfide bonds formed within cytoplasmic proteins to cysteines by serving as an electron donor. In the process, glutathione is converted to its oxidized form, glutathione disulfide (GSSG), also called L-(–)-glutathione.

Once oxidized, glutathione can be reduced back by glutathione reductase, using NADPH as an electron donor. The ratio of reduced glutathione to oxidized glutathione within cells is often used as a measure of cellular oxidative stress.

Function

Glutathione exists in both reduced (GSH) and oxidized (GSSG) states. In the reduced state, the thiol group of cysteine is able to donate a reducing equivalent(H⁺+ e⁻) to other molecules, such as reactive oxygen species to neutralize them, or to protein cysteines to maintain their reduced forms. With donating an electron, glutathione itself becomes reactive and readily reacts with another reactive glutathione to form glutathione disulfide (GSSG). Such a reaction is probable due to the relatively high concentration of glutathione in cells (up to 7 mM in the liver).

Generally, interactions between GSH and other molecules with higher relative electrophilicity deplete GSH levels within the cell. An exception to this case involves the sensitivity of GSH to the electrophilic compound's relative concentration. In high concentrations, the organic molecule diethyl maleate fully depleted GSH levels in cells. However, in low concentrations, a minor decrease in cellular GSH levels was followed by a two-fold increase.

GSH can be regenerated from GSSG by the enzyme glutathione reductase (GSR): NADPH reduces FAD present in GSR to produce a transient FADH-anion. This anion then quickly breaks a disulfide bond (Cys58 – Cys63) and leads to Cys63's nucleophilically attacking the nearest sulfide unit in the GSSG molecule (promoted by His467), which creates a mixed disulfide bond (GS-Cys58) and a GS-anion. His467 of GSR then protonates the GS-anion to form the first GSH. Next, Cys63 nucleophilically attacks the sulfide of Cys58, releasing a GS-anion, which, in turn, picks up a solvent proton and is released from the enzyme, thereby creating the second GSH. So, for every GSSG and NADPH, two reduced GSH molecules are gained, which can again act as antioxidants scavenging reactive oxygen species in the cell.

In healthy cells and tissue, more than 90% of the total glutathione pool is in the reduced form (GSH) and less than 10% exists in the disulfide form (GSSG). An increased GSSG-to-GSH ratio is considered indicative of oxidative stress.

Glutathione has multiple functions:

• It maintains levels of reduced glutaredoxin and glutathione peroxidase.
• It is one of the major endogenous antioxidants produced by the cells, participating directly in the neutralization of free radicals and reactive oxygen compounds, as well as maintaining exogenous antioxidants such as vitamins C and E in their reduced (active) forms.
• Regulation of the nitric oxide cycle is critical for life, but can be problematic if unregulated. Glutathione enhances the function of citrulline as part of the nitric oxide cycle.
• It is used in metabolic and biochemical reactions such as DNA synthesis and repair, protein synthesis, prostaglandin synthesis, amino acid transport, and enzyme activation. Thus, every system in the body can be affected by the state of the glutathione system, especially the immune system, the nervous system, the gastrointestinal system, and the lungs.
• It has a vital function in iron metabolism. Yeast cells depleted of GSH or containing toxic levels of GSH show an intense iron starvation-like response and impairment of the activity of extramitochondrial ISC enzymes thus inhibiting oxidative endoplasmic reticulum folding, followed by death.
• It has roles in progression of the cell cycle, including cell death.GSH levels regulate redox changes to nuclear proteins necessary for the initiation of cell differentiation. Differences in GSH levels also determine the expressed mode of cell death, being either apoptosis or cell necrosis. Manageably low levels result in the systematic breakage of the cell whereas excessively low levels result in rapid cell death.

How Does Glutathione Work?

LGlutathione works in a very simple way, yet other skin whitening products can’t compete with the all-natural amino acid compound. Simply put, Glutathione works to clear the body of free radicals and toxins that can lead to serious skin problems like hyperpigmentation and melasma, as well as more common ones like sun spots.

Additional Benefits of Glutathione

While Glutathione is most commonly used by women looking to whiten their skin, it may have a beneficial effect for women that have cystic acne, acne-prone skin or even the occasional breakout.Glutathione won’t help hormone-related acne in most cases since it doesn’t affect hormone levels in the body, but it is an all-natural chain of amino acids that your body needs. There is evidence now that taking Glutathione could actually help improve a weak immune system or make a healthy immune system even stronger.

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