The activity of ribulose-1,5-bisphosphate carboxylase in various microalgae

The Km (CO2) Rubisco of a variety of algal cells was determined. Typically the Km (CO2) of algal cells falls within the range 30--80 mmol m-3; six of the eight species studied fall within this range. Having calculated the K m (CO2) Rubisco the affinity of the algal cell for CO 2 and the efficiency of its carbon concentrating mechanism were compared. The Km (CO2) Rubisco of two species fell outside of this range; that of Isochrysis galbana had a Km (CO2) 12.71 muM which is usually low for a unicellular alga and that of Chlorella ellipsoiclea mutant ENU 9 was 140 muM which is unusually high for a green alga.;Mechanical breakage of algal cells can cause local heating, which can denature enzymes in the cell extracts. A protocol was designed that reduces such damaging effects. A mixture of cellulysine (5%) and lactase (0.16%) in buffer at pH 6.5 was found to break down the cell walls of the small cells of Chlorophyte and eustigmatophyte algae. Cells were treated with the enzyme mixture at 30°C and evidence of cellular breakage was determined by assaying for carbonic anhydrase (CA) activity using a potentiometric method. An increase of CA activity was observed when cells were further treated with an osmoticum prior to assay. Using this protocol the internal CA activity of Nannochloropsis gaditana, N. oculata and Nannochloris maculata was detected. These algae have been reported not to contain any CA activity.