selenoenzyme

A selenoenzyme is an enzyme that contains selenium as an essential component of its structure and function. Selenium is incorporated into the active site of these enzymes in the form of selenocysteine, an amino acid that is analogous to cysteine but with a selenium atom replacing the sulfur atom. This unique amino acid is encoded directly in the genetic code by a UGA codon, which normally signals a stop codon.

Selenoenzymes play crucial roles in a variety of biological processes, particularly in antioxidant defense and redox regulation. One of the most well-known selenoenzymes is glutathione peroxidase, which protects cells from oxidative damage by catalyzing the reduction of hydrogen peroxide and lipid hydroperoxides. Other important selenoenzymes include thioredoxin reductase, which is involved in the thioredoxin system that reduces disulfide bonds, and deiodinases, which are critical for thyroid hormone metabolism.

The biological importance of selenoenzymes highlights the essential nature of selenium for human and animal health. Deficiencies in selenium can lead to impaired function of these enzymes, potentially contributing to various health issues, including increased susceptibility to oxidative stress and thyroid dysfunction. Conversely, excessive selenium intake can also be toxic, emphasizing the need for a balanced dietary intake. Research continues to explore the diverse functions and therapeutic potential of selenoenzymes.