The plastidic pentose phosphate translocator represents a link between the cytosolic and the plastidic pentose phosphate pathways in plants
The plastidic pentose phosphate translocator represents a link between the cytosolic and the plastidic pentose phosphate pathways in plants
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DOI：
10.1104/pp.010576
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发表时间：
2002-02-01
期刊：
影响因子：
7.4
通讯作者：
Fischer, K
中科院分区：
文献类型：
--
作者：
Eicks, M;Maurino, V;Fischer, K
质体是还原性和氧化性戊糖磷酸途径的位点，两者都产生戊糖磷酸作为中间体。已鉴定出来自拟南芥的质体转运蛋白，其能够与无机磷酸盐或丙糖磷酸盐交换，转运5-磷酸木酮糖（Xul-5-P），并且在较小程度上也转运5-磷酸核酮糖，但不接受5-磷酸核糖或磷酸己糖作为底物。在生理条件下，Xul-5-P将是优选的底物。因此，该转运蛋白被命名为Xul-5-P /磷酸盐转运蛋白（XPT）。XPT与那些磷酸转运子和磷酸烯醇/丙酮酸/磷酸转运子类别的成员仅具有约35%至40%的序列同一性，但与葡萄糖6-磷酸/磷酸转运子具有约50%的较高同一性。因此，它代表了第四组质体磷酸盐转位子。数据库分析表明，植物细胞含有，除了氧化戊糖磷酸途径的氧化分支的酶，核糖5-磷酸异构酶和核酮糖5-磷酸差向异构酶在细胞质和质体，而转酮醇酶和转醛醇酶转化生产的戊糖磷酸磷酸丙糖磷酸和己糖磷酸可能仅限于质体。假设XPT的功能是为质体戊糖磷酸途径提供Xul-5-P形式的胞质碳骨架，特别是在对循环中间体的高需求条件下。
Plastids are the site of the reductive and the oxidative pentose phosphate pathways, which both generate pentose phosphates as intermediates. A plastidic transporter from Arabidopsis has been identified that is able to transport, in exchange with inorganic phosphate or triose phosphates, xylulose 5-phosphate (Xul-5-P) and, to a lesser extent, also ribulose 5-phosphate, but does not accept ribose 5-phosphate or hexose phosphates as substrates. Under physiological conditions, Xul-5-P would be the preferred substrate. Therefore, the translocator was named Xul-5-P /phosphate translocator (XPT). The XPT shares only approximately 35% to 40% sequence identity with members of both the those phosphate translocator and the phosphoeno/pyruvate/phosphate translocator classes but a higher identity of approximately 50% to glucose 6-phosphate/ phosphate translocators. Therefore, it represents a fourth group of plastidic phosphate translocators. Database analysis revealed that plant cells contain, in addition to enzymes of the oxidative branch of the oxidative pentose phosphate pathway, ribose 5-phosphate isomerase and ribulose 5-phosphate epimerase in both the cytosol and the plastids, whereas the transketolase and transaldolase converting the produced pentose phosphates to triose phosphates and hexose phosphates are probably solely confined to plastids. It is assumed that the XPT function is to provide the plastidic pentose phosphate pathways with cytosolic carbon skeletons in the form of Xul-5-P, especially under conditions of a high demand for intermediates of the cycles.