Heldt H W
Horiz Biochem Biophys. 1976;2:199-299.
The chloroplast represents a relatively autonomous metabolic compartment within the plant cell. It is surrounded by an envelope consisting of two membranes of which the inner membrane is the functional barrier. Utilizing the energy of light the chloroplast is able to synthesize dihydroxyacetonephosphate from carbon dioxide and water. To provide the cell with this substrate, inorganic phosphate is required. In the case of phosphate deficiency the product of CO2 fixation may be temporarily stored within the chloroplast as starch. Specific transport processes across the inner envelope membrane permit the transfer of metabolites between the chloroplast and the cytosol. The phosphate translocator facilitates the export of dihydroxyacetone phosphate in exchange for inorganic phosphate. It also catalyzes a shuttle for inorganic phosphate with 3-phosphoglycerate, permitting the indirect transfer of reducing equivalents and of ATP from the chloroplast to the cytosol. The dicarboxylate carrier transporting various dicarboxylates may be suited for the transfer of reducing equivalents from the cytosol into the chloroplast. The ATP translocator, catalyzing a transport of ATP into the chloroplast in exchange for ADP, appears to be important for providing the chloroplast with ATP during the night phase, as required for the mobilization of starch.
叶绿体是植物细胞内一个相对自主的代谢区室。它被一层由两层膜组成的包膜所包围，其中内膜是功能屏障。利用光能，叶绿体能够从二氧化碳和水中合成磷酸二羟丙酮。为了给细胞提供这种底物，需要无机磷酸盐。在磷酸盐缺乏的情况下，二氧化碳固定的产物可能会作为淀粉暂时储存在叶绿体内。跨内膜的特定转运过程允许代谢物在叶绿体和细胞质之间转移。磷酸转运体促进磷酸二羟丙酮的输出，以换取无机磷酸盐。它还催化无机磷酸盐与3-磷酸甘油酸的穿梭，从而使还原当量和ATP从叶绿体间接转移到细胞质中。运输各种二羧酸的二羧酸载体可能适合将还原当量从细胞质转移到叶绿体中。ATP转运体催化ATP进入叶绿体以换取ADP，在夜间阶段为叶绿体提供淀粉动员所需的ATP方面似乎很重要。
