Studies on low oxygen sensitivity mechanism of CAM photosynthesis

CAM光合作用低氧敏感性机制研究

基本信息

批准号：
12460011
负责人：
NOSE Akihiko
金额：
$ 7.94万
依托单位：
Saga University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2003
项目状态：
已结题

项目摘要

The phenomenon in which the depression of CO2 exchange in CAM photosynthesis (phase 3) disappeared under low oxygen conditions, could not be related to CAM subtype of CO2 decarboxylation, that is, PEP carboxykinase (PCK) type and malic enzyme (ME) type. For the oxygen concentration in which the phase 3 of CAM disappears, it has been indicated that cyanide resistant respiration of mitochondria is concerned in low oxygen sensitivity of CAM photosynthesis. However the low oxygen sensitivity of CAM photosynthesis could not be explained simply with cyanide resistant respiration. In the pineapple mitochondria purified with Percoll density method, malic acid was incorporated actively into, the mitochondria only under the condition in which malate/OAA shuttle of the inner membrane functioned. This result indicates that the of malate in the phase 3 dose not operate in the pineapple mitochondria. In addtion, it is suggested that the conversion of malate to OAA in the pineapple mitochondria matrix functions as a replenishment system to supply the OAA as the substrate to the decarboxylation using PCK in the pineapple CAM phase 3. In other words, it is suggestedd that the low oxygen sensitivity of CAM photosynthesis appear only under the condition where the malate in CAM phase 3 is decarboxylated actively by NAD-ME in mitochondria and the NADH produced by the decarboxylation is oxidized with the cyanide resistant respiration.

CAM光合作用（第3阶段）CO2交换抑制在低氧条件下消失的现象，与CAM的CO2脱羧亚型，即PEP羧激酶（PCK）型和苹果酸酶（ME）型无关。对于CAM第3相消失时的氧浓度，表明线粒体的抗氰化物呼吸与CAM光合作用的低氧敏感性有关。然而，CAM 光合作用的低氧敏感性不能简单地用抗氰化物呼吸来解释。在用Percoll密度法纯化的菠萝线粒体中，只有在内膜的苹果酸/OAA穿梭发挥作用的条件下，苹果酸才会主动地掺入线粒体中。该结果表明，第三阶段的苹果酸在菠萝线粒体中不起作用。此外，表明菠萝线粒体基质中苹果酸向OAA的转化起到补充系统的作用，以供应OAA作为菠萝CAM第3相中使用PCK的脱羧的底物。换句话说，表明CAM光合作用的低氧敏感性只有在CAM 3相中的苹果酸被线粒体中的NAD-ME主动脱羧并且脱羧产生的NADH为1的情况下才会出现。与氰化物抗呼吸氧化。