So far, eight different isoforms of glutathione peroxidase (GPx1 8) have been identified in humans.

Glutathione peroxidase 1 (GPx1) is the most abundant version, found in the cytoplasm of nearly all mammalian tissues, whose preferred substrate is hydrogen peroxide.

Myeloperoxidase (MPO) is a peroxidase enzyme that in humans is encoded by the MPO gene.

In animal studies, hepatic glutathione must be depleted to less than 70 of normal levels before hepatotoxicity occurs.

The secondary antibody is usually linked to biotin or to a reporter enzyme such as alkaline phosphatase or horseradish peroxidase.

Glutathione react with the toxic NAPQI metabolite so that it does not damage cells and can be safely excreted.

This is mediated by glutathione and similar compounds in the intestinal wall, the liver and on red blood cells, without the aid of enzymes.

Increased glucose levels, like those seen in diabetes, activates this alternative biochemical pathway, which in turn causes a decrease in glutathione and an increase in reactive oxygen radicals.

The NADPH, used up when the pathway is activated, acts to promote nitric oxide and glutathione production, and its conversion during the pathway leads to reactive oxygen molecules.

Colorimetric detection The colorimetric detection method depends on incubation of the western blot with a substrate that reacts with the reporter enzyme (such as peroxidase) that is bound to the secondary antibody.