Isolation and Some Properties of Ribulose-1, 5-Bisphosphate Carboxylase-Oxygenase from Red Kidney Bean Primary Leaves

Abstract

Purification of ribulose-1,5-bisphosphate carboxylase from primary leaves of Phaseolus vulgaris variety Red Kidney with ammonium sulfate precipitation, ion exchange chromatography and gel filtration resulted in the complete loss of detectable oxygenase activity and the retention of a low velocity and a high Km form of the carboxylase and oxygenase. The polyethylene glycol-6000-purified ribulose-1,5-bisphosphate oxygenase displayed a broad pH optimum (7.9-9.4) and a high Km for O2 and ribulose 1,5-bisphosphate (0.90 mM and 0.25 mM, respectively). Initiation of the oxygenase reaction with protein rather than ribulose 1,5-bisphosphate resulted in reduced activity. The enzymes prepared by the 2 purification procedures were electrophoretically different. Etiolated primary leaf tissue exhibited low rates of carboxylase and oxygenase. Similar developmental kinetic activity was observed for both reactions during greening. Photosynthetic 14CO2 fixation was inhibited 95% by 100% N2 gas during the first 24 h of greening, but the inhibition was rapidly overcome by 48-72 h of light exposure.