Light dependent Activation of NADP malate Dehydrogenase and Photophosphorylation: Energy Requirements
Résumé
The mechanisms of enzyme light activation have been extensively studied in the recent years, but so far, little attention was given to the energetic requirements of this process (Anderson, 1979, Buchanan, 1980). The only recent paper pertaining to this subject (Heber et al., 1982) reported experiments made with protoplasts and intact chloroplasts. The activation of three Calvin cycle enzymes was shown to be saturated at light intensities close to 40 W.m−2. In the present work, we have investigated the energy requirement of another chloroplastic enzyme, the NADP-dependent malate dehydrogenase, in a reconstituted system free of the Calvin cycle regulatory enzymes. This was achieved through the study of light intensity curves and of the ATP formation linked to the light activation.