Kore-eda Shin, Nozawa Akira, Okada Yusuke, Takashi Kazuki, Azad Muhammad Abul Kalam, Ohnishi Jun-ichi, Nishiyama Yoshitaka, Tozawa Yuzuru
Comprehensive Analysis Center for Science, Saitama University, Saitama, Saitama 338-8570, Japan.
Biosci Biotechnol Biochem. 2013;77(7):1511-6. doi: 10.1271/bbb.130174. Epub 2013 Jul 7.
In plant Mesembryanthemum crystallinum, which has the inducible crassulacean acid metabolism (CAM), isoforms of plastidic phosphate translocators (pPTs) are categorized into three subfamilies: the triose phosphate/phosphate translocator (McTPT1), the phosphoenolpyruvate/phosphate translocator (McPPT1), and the glucose 6-phosphate/phosphate translocator (McGPT1 and McGPT2). In order to elucidate the physiological roles of these pPTs in M. crystallinum, we determined the substrate specificity of each pPT isoform. The substrate specificities of McTPT1, McPPT1, and McGPT1 showed overall similarities to those of orthologs that have been characterized. In contrast, for glucose 6-phosphate, McGPT2 showed higher selectivity than McGPT1 and other GPT orthologs. Because the expression of McGTP2 is specific to CAM while that of McGTP1 is constitutively expressed in both the C3- and the CAM-state in M. crystallinum, we propose that McGPT2 functions as a CAM system-specific GPT in this plant.
在具有诱导型景天酸代谢（CAM）的植物冰花（Mesembryanthemum crystallinum）中，质体磷酸转运体（pPTs）的同工型可分为三个亚家族：磷酸丙糖/磷酸转运体（McTPT1）、磷酸烯醇丙酮酸/磷酸转运体（McPPT1）以及葡萄糖6-磷酸/磷酸转运体（McGPT1和McGPT2）。为了阐明这些pPTs在冰花中的生理作用，我们测定了每个pPT同工型的底物特异性。McTPT1、McPPT1和McGPT1对底物的特异性与已鉴定的直系同源物总体相似。相比之下，对于葡萄糖6-磷酸，McGPT2比McGPT1和其他GPT直系同源物表现出更高的选择性。由于McGTP2的表达在冰花中对CAM具有特异性，而McGTP1的表达在C3状态和CAM状态下均组成型表达，我们认为McGPT2在该植物中作为CAM系统特异性GPT发挥作用。
