GPx4フラックスに対する熱力学的制約は、グルタチオンレドックス状態を強迫的死へのコミットメントに結びつける

Ferroptosis is a non-accidental form of cell death driven by lipid peroxidation and critically controlled by the selenoenzyme Glutathione Peroxidase 4 (GPx4). By integrating molecular modeling, redox thermodynamics, and enzymatic evidence, we propose that ferroptosis is governed by the redox potential of the glutathione couple, elevating current mechanistic descriptions to a quantitative physical-chemical framework. The terminal step of the GPx4 catalytic cycle-responsible for enzyme regeneration and oxidized glutathione (GSSG) formation-is intrinsically endergonic, and its driving force declines continuously as the glutathione redox potential becomes less reducing. As a result, GPx4 activity decreases linearly in accordance with Nernstian principle, independently of discrete inhibitory events. Within this framework, ferroptosis is not initiated by a discrete molecular trigger or canonical signaling cascade; rather, it emerges when a critical biological threshold is surpassed, such that GPx4-dependent detoxification capacity is no longer sufficient to counteract ongoing lipid peroxidation within a given pro-oxidant context. Thus, a discrete cell-death outcome executed by GSSG emerges from the continuous variation of a thermodynamic control variable. This mode of regulation is unique to selenium chemistry and provides a physical-chemical rationale for the indispensability of selenocysteine in the redox control of cellular life and death.