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

Agius, Stephanie C LU (2001)
Abstract (Swedish)
Popular Abstract in Swedish

Mitokondrier är små stavformade eller runda organeller (0.5-2 µm). De producerar huvuddelen av den energi som krävs för cellens livsuppehållande processer. Antalet mitokondrier per cell kan variera med vävnadens energibehov. Ett exempel är människans spermie som innehåller ett stort antal mitokondrier vilka behövs för producera den energi som åtgår när spermien simmar till ägget för befruktning. I en växts livscykel är pollenutvecklingen ett av de mest energikrävande stadierna där mitokondriella funktionsstörningar kan orsaka sterilitet.



De mitokondriella proteinerna kan delas in i två huvudgrupper: de som omvandlar energin i socker och fetter till för cellen användbara... (More)
Popular Abstract in Swedish

Mitokondrier är små stavformade eller runda organeller (0.5-2 µm). De producerar huvuddelen av den energi som krävs för cellens livsuppehållande processer. Antalet mitokondrier per cell kan variera med vävnadens energibehov. Ett exempel är människans spermie som innehåller ett stort antal mitokondrier vilka behövs för producera den energi som åtgår när spermien simmar till ägget för befruktning. I en växts livscykel är pollenutvecklingen ett av de mest energikrävande stadierna där mitokondriella funktionsstörningar kan orsaka sterilitet.



De mitokondriella proteinerna kan delas in i två huvudgrupper: de som omvandlar energin i socker och fetter till för cellen användbara energirika molekyler, och de som avger energin i form av värme. Mitokondrierna, som ofta kallas cellens kraftverk, kan därför också sägas vara energislösande. De energislösande proteinernas fysiologisk roll är ännu inte fastlagd, men det är möjligt att de är inblandade i förbränning av ett överskott av kolhydrater.



Nedbrytningen av kolhydrater till koldioxid, vatten och energi i en cell kallas respiration. Vår arbete har gått ut på att undersöka i vilken omfattning energislösande proteiner deltar i respirationen. Dessa proteiner, så kallade NAD(P)H-dehydrogenaser, tar emot elektroner från NADH och NADPH som ursprungligen härrör från nedbrytning av kolföreningar producerade i mitokondrierna eller cytoplasman. I vår undersökning har vi kunnat påvisa att ett NADPH-specifikt, energislösande dehydrogenas deltar i respirationen (Artikel II).



När NADH och NADPH avger elektroner till NAD(P)H-dehydrogenaser bildas NAD+ och NADP+. Dessa föreningar kan i sin tur bli nedbrutna och vi har identifierat mitokondriella proteiner som katalyserar denna reaktion (NAD+-pyrophosphatase) (Artikel I).



I vår undersökning användes också specifika antikroppar för att detektera de energislösande proteinerna (Artikel IV). (Less)
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... (More)
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. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Dr Wagner, A.M., Dept. Mol. Cell Phys., Vrije Universiteit, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Växtbiokemi, Plant biochemistry, antibody, Botanik, NAD-pyrophosphatase, Botany, NADH:ubiquinone oxidoreductase, NADPH dehydrogenase, plant mitochondria, pyridine nucleotides
pages
96 pages
defense location
Department of Plant Physiology, (Lecture Hall), Sölvegatan 35, Lund
defense date
2001-10-05 10:15
external identifiers
  • other:ISRN: LUNBS/(nbfb-1038)/1-(2001)
ISBN
91-7874-143-2
language
English
LU publication?
yes
id
c9009d9e-8042-4ed8-9c0a-e52a1d1e6aab (old id 41878)
date added to LUP
2007-06-20 08:55:21
date last changed
2016-09-19 08:45:15
@phdthesis{c9009d9e-8042-4ed8-9c0a-e52a1d1e6aab,
  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.<br/><br>
<br/><br>
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.<br/><br>
<br/><br>
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.<br/><br>
<br/><br>
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.<br/><br>
<br/><br>
The physiological significance of pyridine nucleotide turnover and occurrence of multiple NAD(P)H dehydrogenases in the inner mitochondrial membrane is discussed.},
  author       = {Agius, Stephanie C},
  isbn         = {91-7874-143-2},
  keyword      = {Växtbiokemi,Plant biochemistry,antibody,Botanik,NAD-pyrophosphatase,Botany,NADH:ubiquinone oxidoreductase,NADPH dehydrogenase,plant mitochondria,pyridine nucleotides},
  language     = {eng},
  pages        = {96},
  school       = {Lund University},
  title        = {Pyridine Nucleotides in Plant Mitochondria. Amounts, metabolism and contribution to electron transport},
  year         = {2001},
}