Re-cycling of glycolate in C3-chloroplasts: Biochemical and physiological effects on plant metabolism

光合作用碳代谢的c2循环从核酮糖1.5-二磷酸羧化酶/加氧酶（Bubiosco）催化的加氧酶反应开始。c2途径的主要功能是通过转化甘油3-P来挽救甘油2-P，甘油3-P重新进入c3还原循环。CO2和NH3都在线粒体内释放，导致c3植物中固定在空气中的CO2损失至少25%。我们尝试在模式植物拟蓝（a . thaliana）（野生型和光呼吸突变体）的叶绿体中引入两个替代的和完整的乙醇酸分解代谢循环，以便在叶绿体中直接释放和重新固定CO2，从而通过增加CO2/O2比来降低Rubisco的加氧酶活性。因此，将创建一个自调节循环，导致光呼吸途径的衰减和预期的二氧化碳同化效率的提高。对携带单一转基因的转化体和具有完全操作的乙醇酸循环的转化体的分析将产生数据，以补充我们对光呼吸途径的功能和调控及其与其他过程（如c3循环，向有机酸的倒转流和NH3再固定）的相互作用的理解。

The C2-cycle of photosynthetic carbon metabolism starts with the oxygenase reaction catalysed by ribulose 1.5-bisphosphate carxboxylase/oxygenase (Bubiosco). The prime function of the C2-pathway is to salvage glycolate 2-P by conversion to glycerate 3-P, which re-enters the C3-reductive cycle. Both CO2 and NH3 are released within the mitochondria, resulting in a loss of at least 25% of the CO2 fixed in abient air in C3-plants. We attempt to introduce two alternative and complete glycolate catabolic cycles into chloroplasts of the model plant A. thaliana (wild-type and a photorespiratory mutant) in order to release and re-fix the CO2 directly within the chloroplast thereby reducing the oxygenase activity of Rubisco by increasing the CO2/O2 ratio. Thus, an autoregulatory cycle would be created which results in an attenuation of the photorespiratory pathway and an expected improvement in the efficiency of CO2 assimilation. Analyses of transformants bearing single transgenes and those with fully operational glycolate cycles will generate data to complement our understanding of function and regulation of the photorespiratory pathway and its interaction with other processes such as the C3-cycle, the anaplerotic flow into organic acids an NH3 refixation.