Department of Veterinary Medical Sciences, Alma Mater Studiorum-University of Bologna, 40064, Ozzano Emilia, Italy.
Department of Health Sciences, Institute of Research for Food Safety and Health (IRC-FSH), University "Magna Græcia" of Catanzaro, 88100, Catanzaro, Italy.
Free Radic Biol Med. 2024 Jan;210:333-343. doi: 10.1016/j.freeradbiomed.2023.11.041. Epub 2023 Dec 4.
Selenite as an inorganic form of selenium can affect the redox state of mitochondria by modifying the thiol groups of cysteines. The FF-ATPase has been identified as a mitochondrial target of this compound. Indeed, the bifunctional mechanism of ATP turnover of FF-ATPase was differently modified by selenite. The activity of ATP hydrolysis was stimulated, whereas the ADP phosphorylation was inhibited. We ascertain that a possible new protein adduct identified as seleno-dithiol (-S-Se-S-) mercaptoethanol-sensitive caused the activation of F-ATPase activity and the oxidation of free -SH groups in mitochondria. Conversely, the inhibition of ATP synthesis by selenite might be irreversible. The kinetic analysis of the activation mechanism was an uncompetitive mixed type with respect to the ATP substrate. Selenite bound more selectively to the FF-ATPase loaded with the substrate by preferentially forming a tertiary (enzyme-ATP-selenite) complex. Otherwise, the selenite was a competitive mixed-type activator with respect to the Mg cofactor. Thus, selenite more specifically bound to the free enzyme forming the complex enzyme-selenite. However, even if the selenite impaired the catalysis of FF-ATPase, the mitochondrial permeability transition pore phenomenon was unaffected. Therefore, the reversible energy transduction mechanism of FF-ATPase can be oppositely regulated by selenite.
亚硒酸盐作为一种无机硒形式，可以通过修饰半胱氨酸的巯基来影响线粒体的氧化还原状态。FF-ATP 酶已被确定为该化合物的线粒体靶标。事实上，亚硒酸盐以不同的方式修饰了 FF-ATP 酶的双功能 ATP 周转机制。ATP 水解的活性被刺激，而 ADP 磷酸化被抑制。我们确定了一种可能的新蛋白质加合物，被鉴定为硒代二硫醇（-S-Se-S-），它对巯基乙醇敏感，导致 F-ATP 酶活性的激活和线粒体中游离 -SH 基团的氧化。相反，亚硒酸盐对 ATP 合成的抑制可能是不可逆的。对激活机制的动力学分析是对 ATP 底物的非竞争性混合类型。亚硒酸盐更选择性地与加载底物的 FF-ATP 酶结合，通过优先形成三级（酶-ATP-亚硒酸盐）复合物。否则，亚硒酸盐是 Mg 辅因子的竞争性混合激活剂。因此，亚硒酸盐更特异性地与游离酶结合形成复合物酶-亚硒酸盐。然而，即使亚硒酸盐损害了 FF-ATP 酶的催化作用，线粒体通透性转换孔现象也不受影响。因此，FF-ATP 酶的可逆能量转导机制可以被亚硒酸盐反向调节。
