Selenoproteins represent a category of selenium-containing proteins characterized by the presence of at least one selenocysteine (Sec/SeCys) residue. In the human body, 25 genetically encoded selenoproteins have been identified, including notable examples such as glutathione peroxidase (GPx), iodinated thyronine deiodinase (DIO), and thioredoxin reductase (TXNRD). These selenoproteins primarily exert diverse physiological functions through enzymatic activities, encompassing roles in antioxidant defenses and metabolic regulation. Their catalytic sites typically feature a selenocysteine

(Sec) residue.