Selenoenzymes

Selenoenzymes are a class of enzymes that require a selenocysteine residue to function as a cofactor. Selenocysteine is a rare amino acid that contains selenium, a trace element essential for human health. In selenoenzymes, selenocysteine is part of the active site, where it plays a crucial role in catalysis and redox reactions.

There are three categories of selenoenzymes, which together constitute approximately 25 of the approximately 400 enzymes in the human genome: glutathione peroxidases (GPx), iodothyronine deiodinases (DIO1, DIO2, and DIO3), and other selenoenzymes involved in thyroid hormone metabolism and redox regulation.

The selenoproteome consists of 25 selenoproteins in the human genome, of which 24 are proteins with a selenocysteine residue. These selenoproteins are involved in various cellular processes, including antioxidant defense, cell growth and development, and the biosynthesis and degradation of thyroid hormones. The functions of these selenoproteins are conserved across eukaryotic organisms, from humans to plants and animals.

Selenium is incorporated into selenoenzymes by the incorporation of selenocysteine tRNA during translation. Selenoenzymes are highly sensitive to oxygen radicals and other harmful substances, and their activity is crucial for maintaining cellular homeostasis. Deficiencies in selenoenzymes have been implicated in various diseases, including Kashin-Beck disease, Keshan disease, and various forms of cancer.

Research on selenoenzymes has led to a better understanding of the role of selenium in human health and disease. Further studies on selenoenzymes and their mechanisms may reveal novel insights into disease pathogenesis and provide new targets for therapeutic intervention.