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Effect of calcium ions and inhibitors on internal NAD(P)H dehydrogenases in plant mitochondria

Rasmusson, A. G. LU and Moller, I. M. (1991) In European Journal of Biochemistry 202(2). p.617-623
Abstract

Both the external oxidation of NADH and NADPH in intact potato (Solanum tuberosum L. cv. Bintje) tuber mitochondria and the rotenone-insensitive internal oxidation of NADPH by inside-out submitochondrial particles were dependent on Ca2+. The stimulation was not due to increased permeability of the inner mitochondrial membrane. Neither the membrane potential nor the latencies of NAD+-dependent and NADP+-dependent malate dehydrogenases were affected by the addition of Ca2+. The pH dependence and kinetics of Ca2+-dependent NADPH oxidation by inside-out submitochondrial particles were studied using three different electron acceptors: O2, duroquinone and ferricyanide.... (More)

Both the external oxidation of NADH and NADPH in intact potato (Solanum tuberosum L. cv. Bintje) tuber mitochondria and the rotenone-insensitive internal oxidation of NADPH by inside-out submitochondrial particles were dependent on Ca2+. The stimulation was not due to increased permeability of the inner mitochondrial membrane. Neither the membrane potential nor the latencies of NAD+-dependent and NADP+-dependent malate dehydrogenases were affected by the addition of Ca2+. The pH dependence and kinetics of Ca2+-dependent NADPH oxidation by inside-out submitochondrial particles were studied using three different electron acceptors: O2, duroquinone and ferricyanide. Ca2+ increased the activity with all acceptors with a maximum at neutral pH and an additional minor peak at pH 5.8 with O2 and duroquinone. Without Ca2+, the activity was maximal around pH 6. The K(m) for NADPH was decreased fourfold with ferricyanide and duroquinone, and twofold with O2 as acceptor, upon addition of Ca2+. The V(max) was not changed with ferricyanide as acceptor, but increased twofold with both duroquinone and O2. Half-maximal stimulation of the NADPH oxidation was found at 3 μM free Ca2+ with both O2 and duroquinone as acceptors. This is the first report of a membrane-bound enzyme inside the inner mitochondrial membrane which is directly dependent on micromolar concentrations of Ca2+. Mersalyl and dicumarol, two potent inhibitors of the external NADH dehydrogenase in plant mitochondria, were found to inhibit internal rotenone-insensitive NAD(P)H oxidation, at the same concentrations and in manners very similar to their effects on the external NAD(P)H oxidation.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
European Journal of Biochemistry
volume
202
issue
2
pages
7 pages
publisher
Wiley-Blackwell
external identifiers
  • Scopus:0025932019
ISSN
0014-2956
DOI
10.1111/j.1432-1033.1991.tb16415.x
language
English
LU publication?
yes
id
72fd8765-5fba-45fb-968e-72a03f9a74ef
date added to LUP
2016-05-31 21:41:00
date last changed
2016-06-01 14:05:18
@misc{72fd8765-5fba-45fb-968e-72a03f9a74ef,
  abstract     = {<p>Both the external oxidation of NADH and NADPH in intact potato (Solanum tuberosum L. cv. Bintje) tuber mitochondria and the rotenone-insensitive internal oxidation of NADPH by inside-out submitochondrial particles were dependent on Ca<sup>2+</sup>. The stimulation was not due to increased permeability of the inner mitochondrial membrane. Neither the membrane potential nor the latencies of NAD<sup>+</sup>-dependent and NADP<sup>+</sup>-dependent malate dehydrogenases were affected by the addition of Ca<sup>2+</sup>. The pH dependence and kinetics of Ca<sup>2+</sup>-dependent NADPH oxidation by inside-out submitochondrial particles were studied using three different electron acceptors: O<sub>2</sub>, duroquinone and ferricyanide. Ca<sup>2+</sup> increased the activity with all acceptors with a maximum at neutral pH and an additional minor peak at pH 5.8 with O<sub>2</sub> and duroquinone. Without Ca<sup>2+</sup>, the activity was maximal around pH 6. The K(m) for NADPH was decreased fourfold with ferricyanide and duroquinone, and twofold with O<sub>2</sub> as acceptor, upon addition of Ca<sup>2+</sup>. The V(max) was not changed with ferricyanide as acceptor, but increased twofold with both duroquinone and O<sub>2</sub>. Half-maximal stimulation of the NADPH oxidation was found at 3 μM free Ca<sup>2+</sup> with both O<sub>2</sub> and duroquinone as acceptors. This is the first report of a membrane-bound enzyme inside the inner mitochondrial membrane which is directly dependent on micromolar concentrations of Ca<sup>2+</sup>. Mersalyl and dicumarol, two potent inhibitors of the external NADH dehydrogenase in plant mitochondria, were found to inhibit internal rotenone-insensitive NAD(P)H oxidation, at the same concentrations and in manners very similar to their effects on the external NAD(P)H oxidation.</p>},
  author       = {Rasmusson, A. G. and Moller, I. M.},
  issn         = {0014-2956},
  language     = {eng},
  number       = {2},
  pages        = {617--623},
  publisher    = {ARRAY(0x8fd3360)},
  series       = {European Journal of Biochemistry},
  title        = {Effect of calcium ions and inhibitors on internal NAD(P)H dehydrogenases in plant mitochondria},
  url          = {http://dx.doi.org/10.1111/j.1432-1033.1991.tb16415.x},
  volume       = {202},
  year         = {1991},
}