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NADH or NADPH ?

  • Susanne Krüger
  • Michael Böttger
Part of the NATO ASI Series book series (NSSA, volume 7)

Summary

Using the method of enzymic cycling, the dynamics of pyridine nucleotide concentrations in maize roots and cultured carrot cells after various treatments were studied. The changes were related to transplasmamembrane electron- and proton- transfer rates measured by a pH — redoxstat.

Ethanol increased H+— efflux and, if plants were pretreated with IAA, electron transfer was enhanced too. It has been proposed that this effect is caused by a rise of NADH content due to the action of ADH. In fact, NADH level increased after ethanol treatment. These results would favour NADH as electron donor for the redox system.

In carrot cells, HCF III treatment decreased both NADH and NADPH levels within five minutes. In maize roots, however, the content of NADH was not affected, but a significant decline of NADPH concentration occured after 30 seconds. Similar results could be obtained with the new electron acceptor hexachloroiridate (IV) in maize roots.

In all these experiments, (NADPH + NADP+] and [NADH + NAD+] remained constant. This indicates that the changes in the contents of the reduced forms really reflect their oxidation rather than alterations of the nucleotide synthesis of the plant. Our results also indicate that NAD-kinase which could link the ATP level with the concentrations of the pyridine nucleotides, does not play a significant role in the nucleotide turnover and in the regulation of the redox pump.

Comparing NAD(P)H concentrations with the rates of electron transfer we conclude that there must be a rapid mechanism for back-regulation of the nucleotide content. Otherwise, the whole pool of reduced nucleotides would be completely oxidized within seconds.

Keywords

Maize Root Pyridine Nucleotide Carrot Cell NADPH Level Enzymic Cycling 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Abbrevations

ADH

alcoholdehydrogenase

HCF III

Hexacyanoferrate III

HCI IV

Hexachloroiridate IV

NBT

Nitrobluetetrazoiium

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Copyright information

© Springer Science+Business Media New York 1988

Authors and Affiliations

  • Susanne Krüger
    • 1
  • Michael Böttger
    • 1
  1. 1.Institut für Allgemeine BotanikHamburg 52Germany

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