Article révisé par les pairs
Résumé : The carboxylase activity of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC was assayed in cowpea (Vigna unguiculata [L.] Walp. var. Bambey 21), a C3 plant, with or without carbonic anhydrase (CA) and ribulose 1,5-bisphosphate (RuBP) added to the reaction mixtures. The apparent K(m) (CO2) and V(max) were determined using the statistical formula of Wilkinson and by the direct linear plot method of Cornish-Bowden and Eisenthal. During the experiments, V(max) remained constant whereas K(m) changed according to the assay conditions. It was found that K(m) (CO2) of Rubisco decreased below the commonly accepted value in the absence of added CA and with high concentrations of RuBP. The variations of K(m) were discussed on the basis of the relative implication of RuBP and CA in the carboxylase activity. The practical applications of these experiments were also highlighted.