Different location in dark-adapted leaves of Phaseolus vulgaris of ribulose-1,5-bisphosphate carboxylase/oxygenase and 2-carboxyarabinitol 1-phosphate.

In situ RuBisCO activity was analyzed in order to determine whether 2-carboxyarabinitol 1-phosphate (CA1P) interacts with the enzyme in dark-adapted leaves of Phaseolus vulgaris. Leaves ground to fine powder in liquid nitrogen were put directly into a reaction mixture containing a saturating concentration of ribulose 1,5-bisphosphate (RuBP) to preserve the activity of RuBisCO which was in the chloroplasts. Some 70% of the total catalytic sites of RuBisCO possessed carboxylase activity in this assay, however, RuBisCO was inhibited in the absence of RuBP. CA1P seemed to be concentrated in the veins. These results indicate that RuBisCO was not complexed with CA1P in leaves.