Fig. 1

Schematic representation of the principles behind the RuBisCO activity assays. The kinetics of the reactions downstream of RuBisCO in the Calvin cycle were monitored to provide RuBisCO activity indirectly. Two distinct assays were developed, A an absorbance based assay in which the kinetics of NADH oxidation was monitored by measuring its absorbance at 340 nm [16], and B RNA sensor-based fluorescence assay using an RNA aptamer which is a Spinach-based ADP sensor. ADP resulting from ATP hydrolysis within the Calvin cycle binds to the recognition module, following which the RNA sensor folds allowing DFHBI binding resulting in a highly fluorescent Spinach-DFHBI complex [17]. 3-PG, 3-phosphoglycerate; 3-PGK, 3- phosphoglycerate kinase; 1,3-BPG, 1,3-bisphosphoglycerate; RuBP, ribulose-1,5-bisphosphate; G-3-P, glyceraldehyde-3-phosphate; GAPN, glyceraldehyde-3-phosphate dehydrogenase; CBB, Calvin-Benson-Bassham cycle