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NAD(P) turnover in plant mitochondria

Agius, Stephanie C; Rasmusson, Allan LU and Møller, Ian M (2001) In Australian Journal of Plant Physiology 28(6). p.461-470
Abstract
An analytical procedure based on alkaline extraction and HPLC analysis was adapted for quantification of pyridine nucleotides in plant mitochondria. The amounts of NAD and NADP extracted from seven different species varied from 1.0 to 3.7 and 0 to 0.5 nmol (mg protein) –1 , respectively. Although NADP was found in four species, its reduced form was in all cases below the detection limit of 0.1 nmol (mg protein) –1 . The NAD pool was mainly oxidized in the absence of substrates. However, oxidation of substrates followed by anaerobiosis caused 50–92% NAD pool reduction, indicating that the majority of the NAD+ was metabolically active. The NAD reduction level in potato tuber mitochondria oxidizing malate varied with assay conditions. The... (More)
An analytical procedure based on alkaline extraction and HPLC analysis was adapted for quantification of pyridine nucleotides in plant mitochondria. The amounts of NAD and NADP extracted from seven different species varied from 1.0 to 3.7 and 0 to 0.5 nmol (mg protein) –1 , respectively. Although NADP was found in four species, its reduced form was in all cases below the detection limit of 0.1 nmol (mg protein) –1 . The NAD pool was mainly oxidized in the absence of substrates. However, oxidation of substrates followed by anaerobiosis caused 50–92% NAD pool reduction, indicating that the majority of the NAD+ was metabolically active. The NAD reduction level in potato tuber mitochondria oxidizing malate varied with assay conditions. The highest level of reduction (>80%) was reached at anaerobiosis, at pH 6.5 and 7.2, conditions favouring malic enzyme (ME), whereas the lowest reduction level (0%) was observed at pH 7.5, conditions favouring malate dehydrogenase (MDH). Mitochondria incubated at 0°C without respiratory substrate showed a loss of endogenous NAD + which correlated with a decline in the rate of oxidation of NAD+ -linked substrates. The lost NAD+ was mainly recovered as breakdown products in both the surrounding medium and the mitochondria. When submitochondrial fractions were incubated with NAD + or NADP + , the highest rate of NAD(P)+metabolism was detected in the outer membrane fraction. The metabolites detected, adenosine monophosphate (AMP), nicotinamide mononucleotide (NMN) and adenosine, imply that several enzymes involved in pyridine nucleotide degradation, including an NAD pyrophosphatase, are localized to the outer membrane. (Less)
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organization
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Contribution to journal
publication status
published
subject
keywords
mitochondria, NAD(P) reduction level, malate oxidation, NAD + metabolism, NAD + pyrophosphatase, phosphodiesterase, NAD(P) amount
in
Australian Journal of Plant Physiology
volume
28
issue
6
pages
461 - 470
publisher
CSIRO Publishing
external identifiers
  • scopus:0034936862
ISSN
0310-7841
DOI
10.1071/PP00155
language
English
LU publication?
yes
id
b42cf8f0-9a60-486a-a8b3-8f0b5da273d3 (old id 42314)
date added to LUP
2007-07-20 14:52:00
date last changed
2018-01-07 06:02:46
@article{b42cf8f0-9a60-486a-a8b3-8f0b5da273d3,
  abstract     = {An analytical procedure based on alkaline extraction and HPLC analysis was adapted for quantification of pyridine nucleotides in plant mitochondria. The amounts of NAD and NADP extracted from seven different species varied from 1.0 to 3.7 and 0 to 0.5 nmol (mg protein) –1 , respectively. Although NADP was found in four species, its reduced form was in all cases below the detection limit of 0.1 nmol (mg protein) –1 . The NAD pool was mainly oxidized in the absence of substrates. However, oxidation of substrates followed by anaerobiosis caused 50–92% NAD pool reduction, indicating that the majority of the NAD+ was metabolically active. The NAD reduction level in potato tuber mitochondria oxidizing malate varied with assay conditions. The highest level of reduction (>80%) was reached at anaerobiosis, at pH 6.5 and 7.2, conditions favouring malic enzyme (ME), whereas the lowest reduction level (0%) was observed at pH 7.5, conditions favouring malate dehydrogenase (MDH). Mitochondria incubated at 0°C without respiratory substrate showed a loss of endogenous NAD + which correlated with a decline in the rate of oxidation of NAD+ -linked substrates. The lost NAD+ was mainly recovered as breakdown products in both the surrounding medium and the mitochondria. When submitochondrial fractions were incubated with NAD + or NADP + , the highest rate of NAD(P)+metabolism was detected in the outer membrane fraction. The metabolites detected, adenosine monophosphate (AMP), nicotinamide mononucleotide (NMN) and adenosine, imply that several enzymes involved in pyridine nucleotide degradation, including an NAD pyrophosphatase, are localized to the outer membrane.},
  author       = {Agius, Stephanie C and Rasmusson, Allan and Møller, Ian M},
  issn         = {0310-7841},
  keyword      = {mitochondria,NAD(P) reduction level,malate oxidation,NAD + metabolism,NAD + pyrophosphatase,phosphodiesterase,NAD(P) amount},
  language     = {eng},
  number       = {6},
  pages        = {461--470},
  publisher    = {CSIRO Publishing},
  series       = {Australian Journal of Plant Physiology},
  title        = {NAD(P) turnover in plant mitochondria},
  url          = {http://dx.doi.org/10.1071/PP00155},
  volume       = {28},
  year         = {2001},
}