Molecular and Cellular Biochemistry

, Volume 51, Issue 2, pp 123–127

NADPH/NADP+ ratio: regulatory implications in yeast glyoxylic acid cycle

  • Jorgina Satrustegui
  • Juan Bautista
  • Alberto Machado
Article

DOI: 10.1007/BF00230397

Cite this article as:
Satrustegui, J., Bautista, J. & Machado, A. Mol Cell Biochem (1983) 51: 123. doi:10.1007/BF00230397

Summary

The utilization by yeast of two carbon sources is carried out through the operation of the glyoxylic acid cycle. Kinetic data from the isocitrate transforming enzymes suggest that the flow of isocitrate through the glyoxylic acid cycle depends upon the inhibition of the isocitrate decarboxylating enzymes. Both isocitrate dehydrogenases are inhibited by a mixture of glyoxylate + oxaloacetate, but for the reasons described in the text we consider that this inhibition is of no physiological significance. On the other hand, we have found that NADPH is a competitive inhibitor of NADP-isocitrate dehydrogenase with respect to NADP+, with a KI similar to its KM. It also produces an additive effect on the NADH-produced inhibition of NAD-isocitrate dehydrogenase. We propose NADPH as the compound that channels the utilization of isocitrate into the glyoxylic acid cycle. This is supported by the finding of an increased NADPH/NADP+ ratio in acetate grown yeast with respect to glucose grown cells.

Copyright information

© Martinus Nijhoff Publishers 1983

Authors and Affiliations

  • Jorgina Satrustegui
    • 1
  • Juan Bautista
    • 1
  • Alberto Machado
    • 1
  1. 1.Departamento de Bioquímica y Biología Molecular, Centro de Biología MolecularUniversidad AutónomaCantoblanco, MadridSpain