While in heterotrophic cells and in darkness mitochondria serve as main producers of energy, during photosynthesis this function is transferred to chloroplasts and the main role of mitochondria in bioenergetics turns to be the balance of the level of phosphorylation of adenylates and of reduction of pyridine nucleotides to avoid over-energization of the cell and optimize major metabolic fluxes. This is achieved via the establishment and regulation of local equilibria of the tricarboxylic acid (TCA) cycle enzymes malate dehydrogenase and fumarase in one branch and aconitase and isocitrate dehydrogenase in another branch. In the conditions of elevation of redox level, the TCA cycle is transformed into a non-cyclic open structure (hemicycle) leading to the export of the tricarboxylic acid (citrate) to the cytosol and to the accumulation of the dicarboxylic acids (malate and fumarate). While the buildup of NADPH in chloroplasts provides operation of the malate valve leading to establishment of NADH/NAD+ ratios in different cell compartments, the production of NADH by mitochondria drives citrate export by establishing conditions for the operation of the citrate valve. The latter regulates the intercompartmental NADPH/NADP+ ratio and contributes to the biosynthesis of amino acids and other metabolic products during photosynthesis.

中文翻译：

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柠檬酸阀将线粒体整合到光合代谢中

虽然在异养细胞和黑暗中线粒体作为能量的主要生产者，但在光合作用过程中，这一功能被转移到叶绿体，线粒体在生物能量学中的主要作用变成了腺苷酸磷酸化水平和吡啶核苷酸还原水平的平衡。避免细胞过度供能并优化主要代谢通量。这是通过在一个分支中建立和调节三羧酸 (TCA) 循环酶苹果酸脱氢酶和延胡索酸酶以及在另一个分支中的乌头酸酶和异柠檬酸脱氢酶的局部平衡来实现的。在氧化还原水平升高的条件下，TCA 循环转化为非环状开放结构（半环），导致三羧酸（柠檬酸盐）输出到细胞质并积累二羧酸（苹果酸和富马酸）。虽然 NADPH 在叶绿体中的积累提供了苹果酸阀的操作，导致在不同的细胞隔室中建立 NADH/NAD+ 比率，但线粒体产生的 NADH 通过为柠檬酸阀的运行建立条件来驱动柠檬酸盐的输出。后者调节隔室间 NADPH/NADP+ 比率，并有助于光合作用过程中氨基酸和其他代谢产物的生物合成。虽然 NADPH 在叶绿体中的积累提供了苹果酸阀的操作，导致在不同的细胞隔室中建立 NADH/NAD+ 比率，但线粒体产生的 NADH 通过为柠檬酸阀的运行建立条件来驱动柠檬酸盐的输出。后者调节隔室间 NADPH/NADP+ 比率，并有助于光合作用过程中氨基酸和其他代谢产物的生物合成。虽然 NADPH 在叶绿体中的积累提供了苹果酸阀的运行，导致在不同的细胞隔室中建立 NADH/NAD+ 比率，但线粒体产生的 NADH 通过为柠檬酸阀的运行建立条件来驱动柠檬酸盐的输出。后者调节隔室间 NADPH/NADP+ 比率，并有助于光合作用过程中氨基酸和其他代谢产物的生物合成。