活生物体在氧化还原酶的活性位点主要以硒代半胱氨酸的形式使用硒。这里,硒的独特的化学被认为是调节反应机制和提高催化效率的特定酶的方式无法实现的含硫半胱氨酸。然而,尽管硒/硫具有不同的物理化学性质,一些硒蛋白具有功能齐全的含半胱氨酸的同源物,一些生物体根本不使用硒代半胱氨酸.在这次审查中,选择含硒代半胱氨酸的蛋白质将被讨论以展示这两种情况:(i)硒作为蛋白质的生理功能的必需元素,和(ii)硒与硫(含硒或硫的功能性蛋白质)相比没有明显优势。硒在抗氧化防御中的生理作用(维持细胞氧化还原状态/阻碍氧化应激),激素代谢,DNA合成,和修复(保持遗传稳定性)也将被强调,以及硒对人体健康的作用。甲酸脱氢酶,氢化酶,谷胱甘肽过氧化物酶,硫氧还蛋白还原酶,和碘甲状腺原氨酸脱碘酶将在这里的特点。
Living organisms use selenium mainly in the form of selenocysteine in the active site of oxidoreductases. Here, selenium\'s unique chemistry is believed to modulate the reaction mechanism and enhance the catalytic efficiency of specific enzymes in ways not achievable with a sulfur-containing cysteine. However, despite the fact that selenium/sulfur have different physicochemical properties, several selenoproteins have fully functional cysteine-containing homologues and some organisms do not use selenocysteine at all. In this review, selected selenocysteine-containing proteins will be discussed to showcase both situations: (i) selenium as an obligatory element for the protein\'s physiological function, and (ii) selenium presenting no clear advantage over sulfur (functional proteins with either selenium or sulfur). Selenium\'s physiological roles in antioxidant defence (to maintain cellular redox status/hinder oxidative stress), hormone metabolism, DNA synthesis, and repair (maintain genetic stability) will be also highlighted, as well as selenium\'s role in human health. Formate dehydrogenases, hydrogenases, glutathione peroxidases, thioredoxin reductases, and iodothyronine deiodinases will be herein featured.