The reducing equivalents NADH and FADH₂ are essential products of the TCA that were used by the electron transport chain (ETC) to generate ATP through oxidative phosphorylation (Chandel 2020a). But an often-overlooked reducing equivalent is NADPH, which is not used for generating ATP but for biosynthesis of macromolecules. NADPH is the major reducing equivalent driving de novo synthesis of fatty acids, cholesterol, amino acids, and nucleotides. Its other major function is generation of superoxide (O₂⁻) by NADPH oxidases (NOXs) and scavenging of H₂O₂ by regenerating GSH and the antioxidant protein thioredoxin (TRX). Its role in generating superoxide and scavenging H₂O₂ will be covered in this review, and the biosynthetic reactions coupled to NADPH will be covered in other reviews in this collection.

中文翻译：

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NADPH——被遗忘的还原当量

还原当量 NADH 和 FADH ₂是 TCA 的必需产物，电子传递链 (ETC) 使用它们通过氧化磷酸化生成 ATP ( Chandel 2020a )。但一个经常被忽视的还原当量是 NADPH，它不用于生成 ATP，而是用于大分子的生物合成。NADPH 是驱动脂肪酸、胆固醇、氨基酸和核苷酸从头合成的主要还原当量。它的另一个主要功能是通过 NADPH 氧化酶 (NOX) 产生超氧化物 (O ₂ ^- ) 并通过再生 GSH 和抗氧化蛋白硫氧还蛋白 (TRX)清除 H ₂ O _{2 。}其在产生超氧化物和清除H ₂ O中的作用₂将在本评论中介绍，与 NADPH 耦合的生物合成反应将在本系列的其他评论中介绍。