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Is Glutathione The Ultimate Antioxidant?

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Along with its well-known function combating oxidative stress through its role as a critical source of reducing power, Glutathione (GSH) is involved in a number of diverse functions including apoptosis, disulfide bond formation, detoxification, antioxidant defense, maintenance of thiol status, and modulation of cell proliferation. GSH is a tripeptide (gamma-L-glutamyl-L-cysteinylglycine) and the central cysteine group in the backbone is essential in the regulation of disulfide bonds of proteins and in the disposal of electrophiles and oxidants. The antioxidant function of GSH is modulated through the redox-active thiol group which becomes oxidized when GSH reduces target molecules. The importance of GSH as a cellular redox buffer is underscored by the fact that GSH displays a low redox potential and is found in millimolar concentrations in cells. GSH depletion is an early indicator of programmed cell death in response to a variety of apoptotic stimuli. The exact role of GSH depletion in apoptosis requires further study, but the decrease in cellular reducing power is a clear indicator of the initiation of programmed cell death.

Glutathione exists in both the thiol-reduced (GSH) form and the disulfide-oxidized (GSSG) form. In the reduced state, the thiol group of cysteine is able to donate an electron to other molecules. The electron donation can affect the receiving molecule in varying ways including neutralizing reactive oxygen species or maintaining cysteine in reduced forms of protein. GSH can be regenerated from GSSG by the enzyme glutathione reductase. Although over 90% of glutathione exists in the GSH form, a true assessment of total glutathione concentration and oxidative stress requires the measurement of both GSH and GSSG. The ratio of GSH to GSSG can be altered by a number of factors including disease state or oxidative stressors.

Recently, oxidative stress responses have been increasingly implicated in a variety of diseases. There has been corresponding interest in GSH measurement and more labs are using GSH:GSSG ratios as an indicator of oxidative stress. Routine detection of the free thiol group of reduced glutathione (GSH) is now fairly common. However, GSSG is present at a much lower concentration than GSH and typically requires an additional reduction reaction in order to be measured. The Arbor Assays DetectX® Glutathione Fluorescent Detection Kit simplifies glutathione detection by allowing measurement of Free (GSH) and Total Glutathione (GSH + GSSG) in same well with the same sample, marking a significant advancement in GSH:GSSG ratio detection methods and a considerable improvement over previous techniques.

The versatility and benefits of Arbor Assays kits for GSH:GSSG ratio detection has been thoroughly demonstrated in a number of recent studies on Heart FailureKidney Disease, Diabetes, and Alzheimer’s Disease. The detection kits are available in standard 96-well (K006-F1/F5) as well as 384-well (K006-F1D) formats for high throughput screening applications.

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