Abstract
The light-dependent inhibition of glucose-6-phosphate dehydrogenase (EC 1.1.1.49), the key enzyme of the oxidative pentose phosphate cycle, can be gradually abolished in an illuminated reconstituted spinach chloroplast system by increasing the concentration of NADP+. The inhibition caused by the effector which was produced by the system in the light is characterized as being of the competitive type with respect to NADP+. The Ki value is 0.070 mM. The addition of NADPH to the illuminated reconstituted system results in a further decrease of the enzyme activity. Again, the type of inhibition is a competitive one, the Ki value being 0.072 mM. In the presence of dithiothreitol (DTT) alone the inhibition is incomplete, non-competitive, and the Ki value is as high as 0.2 mM. From the data presented it is concluded that light modulation of chloroplast glucose-6-phosphate dehydrogenase is mainly achieved by the NADPH/NADP+ ratio. Disulfide reduction processes induced by a DTT-type compound seem to play a minor physiologic role during illumination.
Originalsprache | Englisch |
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Seiten (von - bis) | 1-6 |
Seitenumfang | 6 |
Fachzeitschrift | Planta |
Jahrgang | 148 |
Ausgabenummer | 1 |
DOIs | |
Publikationsstatus | Veröffentlicht - Feb. 1980 |