Effects of the calvin cycle on nicotinamide adenine dinucleotide concentrations and redox balances of Xantobacter flavus

The levels of reduced and oxidized nicotinamide adenine dinucleotides were determined in Xanthobacter flavus during a transition from heterotrophic to autotrophic growth. Excess reducing equivalents are rapidly dissipated fol lowing induction of the Calvin cycle, indicating that the Calvin cycle serv es as a sink for excess reducing equivalents. The physiological data suppor t the conclusion previously derived from molecular studies in that expressi on of the Calvin cycle genes is controlled by the intracellular concentrati on of NADPH.