[The light-induced synthesis of the NADP(+)-dependent glycerin-aldehyde-3-phosphate-dehydrogenase : III. The importance of chlorophyll and the influence of metabolic inhibitors].

1. A chlorophyll-less Pisum sativum mutant showed - in contrast to the normal form - no increase in the activity of the NADP(+)-dependent glycerinaldehyde-3-phosphate-dehydrogenase following illumination. 2. In both forms of Pisum the amount of the enzyme present in the dark was about equal. 3. DCMU, an inhibitor of the noncyclic electron flow in photosynthesis reduces the light-induced synthesis of the enzyme to about half in a concentration of 10(-6) m and inhibits it totally at higher concentrations. The dark values of enzyme activity were not influenced by the presence of the inhibitor. 4. Salicylaldoxime also blocks the enzyme synthesis in the light; this effect increases with increasing concentration of the inhibitor. The inhibition is complete at a concentration of 5 · 10(-4) m. 5. Sodium azide in a concentration of 10(-3) m inhibits the photosynthesis and the light-induced GPD-synthesis almost completely; respiration is diminished by more than 50% whereas the dark value of the GPD-activity remains unchanged. 6. 2,4-Dinitrophenol in a low concentration (10(-6) m) increased the oxygen consumption in the dark considerably, but the photosynthesis only slightly. The light synthesis of the enzyme was not affected, nor was the dark value influenced. At a concentration of 10(-5) m there was a slight decrease in respiration and a greater decrease in the photosynthesis. The dark value of the GPD was not different from that of the controls whereas the synthesis in the light was markedly diminished. A concentration of 10(-4) m completely blocks the respiration, the photosynthesis, and the light-induced GPD-synthesis; the dark value is decreased to about 50%. 7. It is concluded that the reversible synthesis of the NADP(+)-dependent GPD in light is dependent on chlorophyll and on an intact photosynthesis; the decisive reaction in this connection is the photoreaction II, the noncyclic electron flow.