Methylselenol Formed by Spontaneous Methylation of Selenide Is a Superior Selenium Substrate to the Thioredoxin and Glutaredoxin Systems
Figure 8
Proposed schematic overview of the spontaneous methylation of selenide to methylselenol.
A schematic diagram showing the individual role of selenite, thioredoxin and glutaredoxin system and SAM in redox cycling of selenium intermediate metabolites. Selenite is reduced to hydrogen selenide either by thioredoxin or glutaredoxin system (reaction 1) [8], [9]. The same reaction can be catalyzed either by glutathione or cysteine, resulting into the same final end product. Hydrogen selenide can successively be oxidized by oxygen to form superoxide radical or undergo redox cycling mediated by thioredoxin or glutaredoxin system (reaction 2) [8], [9]. However, hydrogen selenide can spontaneously react with SAM to form methylselenol (reaction 3). Subsequently, the thioredoxin and glutaredoxin system participate in the redox cycling of methylselenol in a similar way (reaction 4) with that of hydrogen selenide and generate reactive oxygen species. Under reducing environment, monomethylselenol may act as a radical scavenger because of its superior nucleophilicity compared to its counterpart hydrogen selenide.