Selenoenzyme

Selenoenzymes are a subset of selenoproteins characterized by their catalytic activity, owing to the incorporation of the amino acid selenocysteine (Sec) at their active site[2]. These enzymes are essential for multiple biological functions, particularly antioxidation, cellular redox regulation, and thyroid hormone metabolism[1][4]. Notable selenoenzymes include glutathione peroxidases, thioredoxin reductases, and deiodinases, each playing key roles in neutralizing reactive oxygen species, maintaining intracellular reducing conditions, and regulating endocrine pathways[1][4][5]. In humans, at least 25 genetically unique selenoprotein genes have been identified, with several functioning as selenoenzymes. Dysregulation or inhibition of selenoenzyme activity is implicated in diverse diseases, such as cancer, neurodegenerative disorders, inflammatory conditions, and especially in thyroid pathology due to their roles in hormone activation/deactivation[1][5][4]. Selenoenzyme function can be monitored via protein activity measurements and selenium levels, and while selenium supplementation can be therapeutic, excessive intake poses toxicity risks.

Other names

Selenoprotein (when referring to the enzymatically active subset)Selenium-dependent enzymeSec-containing enzymeSelenium enzyme

Oxidation/reduction of peroxide species (e.g. H₂O₂ breakdown by glutathione peroxidase)[4]; Redox cycling and maintenance of cellular redox state (e.g. thioredoxin reductase activity); Catalysis of thyroid hormone activation/inactivation (by deiodinases)[1][4]