RUBISCO ACTIVASE ACTIVITY IN SPINACH LEAF EXTRACTS

Rubisco activase is a chloroplast stromal protein that catalyzes the activation of ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) in vivo. Activation must occur before rubisco can catalyze the photosynthetic assimilation of CO2. In leaves, photosynthesis and rubisco activation increase with increasing light intensity. Techniques are described that allow the activity of rubisco activase to be measured in extracts of spinach (Spinacea oleracea L.) leaf tissue. In this context, rubisco activase activity is defined as the ability to promote activation of the inactive ribulose-1,5-bisphosphate-bound rubisco in an ATP-dependent reaction. Determination of rubisco activase activity in extracts of dark and light treated leaf tissue revealed that the activation state of rubisco activase was independent of light intensity.