Pyridine Nucleotides in Plant Mitochondria. Amounts, metabolism and contribution to electron transport

Stephanie C Agius

Research output: ThesisDoctoral Thesis (compilation)

82 Downloads (Pure)

Abstract

HPLC analysis was used for direct quantification of amounts and redox levels of pyridine nucleotides in plant mitochondria. The amount of NAD(H) and NADP+ varied, 1.0-3.7 and 0-0.5 nmol (mg protein)-1, respectively, depending on the species from which nucleotides were extracted. NADPH was never detected.

Submitochondrial localisation of NAD+-degrading enzymes indicated that matrix NAD+ diffuses intact across the inner mitochondrial membrane and is metabolised by NAD+-catabolising enzymes in the outer membrane. NAD pyrophosphatase activity was identified as being involved in the pyridine nucleotide degradation.

During malate oxidation by isolated Solanum tuberosum mitochondria, the highest levels of NAD(H) reduction were obtained when malic enzyme was active. The lowest NAD(H) reduction levels were seen when conditions favoured malate dehydrogenase activity. Rotenone increased the reduction level of intramitochondrial NADH. Diphenylene iodonium (DPI) inhibited malate oxidation in the presence of rotenone in isolated mitochondria. This result indicated participation of matrix NADPH and the internal rotenone-insensitive, DPI-sensitive, NADPH dehydrogenase during malate oxidation.

Antisera raised against peptides deduced from two S. tuberosum genes (nda1 and ndb1), homologous to the yeast genes for the internal and external NADH:ubiquinone dehydrogenases specifically cross-reacted with 48 and 61 kDa polypeptides in potato tuber mitochondria, respectively. Native NDA1 and NDB1 occurred as higher molecular mass forms, and show different association to the inner mitochondrial membrane.

The physiological significance of pyridine nucleotide turnover and occurrence of multiple NAD(P)H dehydrogenases in the inner mitochondrial membrane is discussed.
Original languageEnglish
QualificationDoctor
Awarding Institution
  • Department of Biology
Supervisors/Advisors
  • [unknown], [unknown], Supervisor, External person
Award date2001 Oct 5
Print ISBNs91-7874-143-2
Publication statusPublished - 2001

Bibliographical note

Defence details

Date: 2001-10-05
Time: 10:15
Place: Department of Plant Physiology, (Lecture Hall), Sölvegatan 35, Lund

External reviewer(s)

Name: Wagner, A.M.
Title: Dr
Affiliation: Dept. Mol. Cell Phys., Vrije Universiteit, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands

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The information about affiliations in this record was updated in December 2015.
The record was previously connected to the following departments: Biology building (Closed 2011) (011008000)

Subject classification (UKÄ)

  • Biological Sciences

Keywords

  • Växtbiokemi
  • Plant biochemistry
  • antibody
  • Botanik
  • NAD-pyrophosphatase
  • Botany
  • NADH:ubiquinone oxidoreductase
  • NADPH dehydrogenase
  • plant mitochondria
  • pyridine nucleotides

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