PDF(Pubmed)
Abstract：
Rubisco activity is highly regulated and frequently limits carbon assimilation in crop plants. In the chloroplast, various metabolites can inhibit or modulate Rubisco activity by binding to its catalytic or allosteric sites, but this regulation is complex and still poorly understood. Using rice Rubisco, we characterised the impact of various chloroplast metabolites which could interact with Rubisco and modulate its activity, including photorespiratory intermediates, carbohydrates, amino acids; as well as specific sugar-phosphates known to inhibit Rubisco activity - CABP (2-carboxy-d-arabinitol 1,5-bisphosphate) and CA1P (2-carboxy-d-arabinitol 1-phosphate) through in vitro enzymatic assays and molecular docking analysis. Most metabolites did not directly affect Rubisco in vitro activity under both saturating and limiting concentrations of Rubisco substrates, CO2 and RuBP (ribulose-1,5-bisphosphate). As expected, Rubisco activity was strongly inhibited in the presence of CABP and CA1P. High physiologically relevant concentrations of the carboxylation product 3-PGA (3-phosphoglyceric acid) decreased Rubisco activity by up to 30%. High concentrations of the photosynthetically derived hexose phosphates fructose 6-phosphate (F6P) and glucose 6-phosphate (G6P) slightly reduced Rubisco activity under limiting CO2 and RuBP concentrations. Biochemical measurements of the apparent Vmax and Km for CO2 and RuBP (at atmospheric O2 concentration) and docking interactions analysis suggest that CABP/CA1P and 3-PGA inhibit Rubisco activity by binding tightly and loosely, respectively, to its catalytic sites (i.e. competing with the substrate RuBP). These findings will aid the design and biochemical modelling of new strategies to improve the regulation of Rubisco activity and enhance the efficiency and sustainability of carbon assimilation in rice.
摘要：
Rubisco活性受到高度调节，并经常限制作物中的碳同化。在叶绿体中，各种代谢物可以通过结合其催化或变构位点来抑制或调节Rubisco活性，但是这项规定很复杂，仍然知之甚少。用大米Rubisco,我们表征了各种叶绿体代谢物的影响，这些叶绿体代谢物可以与Rubisco相互作用并调节其活性，包括光呼吸中间体，碳水化合物,氨基酸;以及已知抑制Rubisco活性的特定糖磷酸盐-CABP（2-羧基-D-阿拉伯糖醇1,5-二磷酸）和CA1P（2-羧基-D-阿拉伯糖醇1-磷酸）通过体外酶测定和分子对接分析。在饱和和极限浓度的Rubisco底物下，大多数代谢物都不会直接影响Rubisco的体外活性，CO2和RuBP(1,5-双磷酸核糖)。不出所料,在CABP和CA1P存在下，Rubisco活性受到强烈抑制。高生理相关浓度的羧化产物3-PGA（3-磷酸甘油酸）可使Rubisco活性降低多达30％。高浓度的光合衍生的磷酸己糖果糖6-磷酸（F6P）和葡萄糖6-磷酸（G6P）在有限的CO2和RuBP浓度下略微降低了Rubisco的活性。CO2和RuBP（在大气O2浓度下）的表观Vmax和Km的生化测量和对接相互作用分析表明，CABP/CA1P和3-PGA通过紧密和松散的结合来抑制Rubisco活性，分别,到其催化位点(即，与底物RuBP竞争)。这些发现将有助于新策略的设计和生化建模，以改善Rubisco活性的调节，并提高水稻碳同化的效率和可持续性。
