The role of NAD+ in the metabolic regulation of nitrogenase, the ‘switch-off’ effect, in Rhodospirillum rubrum has been studied. We now show that the decrease in nitrogenase activity upon addition of NAD+ to R. rubrum is due to modification of dinitrogenase reductase. There was no effect when NAD+ was added to a mutant of R. rubrumdevoid of dinitrogenase reductase ADP-ribosyltransferase, indicating that NAD+ ‘switch-off’ is an effect of the same regulatory system as ammonium ‘switch-off’. We also show that oxaloacetate and α-ketoglutarate function as ‘switch-off’ effectors. On the other hand β-hydroxybutyrate has the opposite effect by shortening the ‘switch-off’ period. Furthermore, by using an inhibitor of glutamate synthase the role of this enzyme in ‘switch-off’ was investigated. The results are discussed in relation to our proposal that changes in the concentration of NAD+ are involved in initiating ‘switch-off’.
Research Article| March 15 1997
The role of NAD+ as a signal during nitrogenase switch-off in Rhodospirillum rubrum
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Agneta NORÉN, Abdelhamid SOLIMAN, Stefan NORDLUND; The role of NAD+ as a signal during nitrogenase switch-off in Rhodospirillum rubrum. Biochem J 15 March 1997; 322 (3): 829–832. doi: https://doi.org/10.1042/bj3220829
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