Fig. 2

RuBisCO activity was estimated through an NADH-based assay using two inorganic carbon substrates, A NaHCO₃, B CO₂, in conjunction with RuBP, and varying amounts of crude protein (50, 100, 150, 200 µg). C Reaction rates were calculated as mmol of RuBP consumed per minute and compared between reactions supplemented with CO₂ and bicarbonate as inorganic C substrates. The reaction rates supplemented with CO₂ were significantly higher than those for bicarbonate. D Comparative analysis of RuBisCO activities with CO₂ as a substrate, estimated in terms of photosynthetic NADH oxidation per µg of Chl-a per minute, as a function of variable amounts of cyanobacterial crude protein. The results indicated that the highest activity was observed with 50 µg of the total protein. All the assays were performed in biological triplicates and statistically significant differences (presented as *, relative to the highest estimation under consideration) were determined using the Student’s t-test, p < 0.05