CHLOROPLAST RIBULOSE-5-PHOSPHATE KINASE - LIGHT-MEDIATED ACTIVATION, AND DETECTION OF BOTH SOLUBLE AND MEMBRANE-ASSOCIATED ACTIVITY

Phosphoribulokinase from spinach chloroplasts held in darkness was inactive when measured at pH 6.8 but active when measured at pH 7.8. Following the onset of illumination of the chloroplasts, the enzyme activity measured at either pH increased rapidly. Significant activation by dithiothreitol was observed only at pH 7.8 with enzyme from chloroplasts held in darkness. A portion of the total phosphoribulokinase can be pelleted by centrifugation after chloroplast breakage, irrespective of whether or not the chloroplasts were illuminated immediately prior to breakage. The pelleted activity could be easily solubilised by extraction with buffer. © 1979.