Etude de l'evolution de la malate deshydrogenase a NADP durant le verdissement des feuilles de Phaseolus vulgaris L

Abstract The evolution of NADP-dependent malate dehydrogenase (MDH) activity was examined during the greening of primary leaves of Phaseolus vulgaris . The enzyme was present in material grown in darkness; upon illumination, the specific activity reached a level two to six times higher than of etiolated material. During the same time, NAD dependent MDH activity remained unchanged whereas the level of NADP dependent G-3P-DH increased tenfold. After the dark-light transition, D -threo-chloramphenicol had no effect on the evolution of enzyme actvities. This suggests that the enhancement of the catalytic power of these chloroplastic enzymes does not result from de novo protein synthesis but more probably from the activation, under light control, of pre-existing molecules.