Selenoproteins Classification and Functions

Table 1 lists the selenoproteins that have been unequivocally identified in mammals, together with a summary of their main locations and known functions. Of the known glutathione peroxidases, three are tetramers and one (the phospholipid hydroperoxide-specific peroxidase) is monomeric in its quaternary structure. It appears to be this class of enzymatic activity that is critical for the action of selenoproteins in maintaining immune function, and indeed, glutathione peroxidase type I knockout mice are susceptible to viral mutation and increased viral virulence, as are selenium-deficient ones. Several other selenoproteins listed in Table 1 also have antioxidant functions and activities. Reaction of glutathione peroxidase with peroxides yields selenic or seleninic acid at the active site of the enzyme, which is recycled by glutathione.

The three thioredoxin reductases act in conjunction with the sulfur protein thioredoxin and with NADPH to bind key transcription factors to DNA. The iodothyronine deiodinases modulate the thyroid hormones, helping to ensure an optimal supply of the

Table 1 Selenoprotein description and functions


Molecular description


Glutathione peroxidases (GPx)

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