Competing carboxylases: circadian and metabolic regulation of Rubisco in C3 and CAM Mesembryanthemum crystallinum L.
Competing carboxylases: circadian and metabolic regulation of Rubisco in C3 and CAM Mesembryanthemum crystallinum L.
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DOI：
10.1111/j.1365-3040.2012.02483.x
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发表时间：
2012-07-01
影响因子：
7.3
通讯作者：
Griffiths, H.
中科院分区：
文献类型：
--
作者：
Davies, B. N.;Griffiths, H.
中胚草核酮糖1中心点5-二磷酸羧化酶/加氧酶（Rubisco）和磷酸烯醇式丙酮酸羧化酶（PEPc）活性的时间协调性在常规光暗（LD）和连续光照（LL）条件下，研究了C3和景天科植物酸代谢（CAM）模式。当C3时，在LL下的每个主观夜晚，净CO2同化率增加，最大羧化与Rubisco活化状态无关。CAM的昼夜节律的CO2吸收更明显，与CO2同化率最大对每个主观的夜晚结束。在体内和体外技术集成映射羧化酶的酶调节CAM LL气体交换活性提供的框架。Rubisco在体外整个主观黑暗时期被激活，并且在每个主观黎明时始终失活，类似于在组成性CAM物种中在真正黎明时观察到的。瞬时碳同位素歧视显示在体内羧化酶共显性在CAM主观的夜晚，最初由Rubisco和后来的C4（PEPc），尽管这两种酶似乎在体外激活。可滴定酸度积累的昼夜节律在连续的主观夜晚逐渐减弱，但PEPc羧化能力的维持确保CAM植物不会随着LL下的时间逐渐变得更像C3。
The temporal co-ordination of ribulose 1 center dot 5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPc) activities by Mesembryanthemum crystallinum L. in C3 and crassulacean acid metabolism (CAM) modes was investigated under conventional light-dark (LD) and continuous light (LL) conditions. When C3, net CO2 assimilation rate increased during each subjective night under LL with maximum carboxylation unrelated to Rubisco activation state. The CAM circadian rhythm of CO2 uptake was more pronounced, with CO2 assimilation rate maximal towards the end of each subjective night. In vivo and in vitro techniques were integrated to map carboxylase enzyme regulation to the framework provided by CAM LL gas exchange activity. Rubisco was activated in vitro throughout each subjective dark period and consistently deactivated at each subjective dawn, similar to that observed at true dawn in constitutive CAM species. Instantaneous carbon isotope discrimination showed in vivo carboxylase co-dominance during the CAM subjective night, initially by Rubisco and latterly C4 (PEPc), despite both enzymes seemingly activated in vitro. The circadian rhythm in titratable acidity accumulation was progressively damped over successive subjective nights, but maintenance of PEPc carboxylation capacity ensures that CAM plants do not become progressively more C3-like with time under LL.