Effect of calcium ions and inhibitors on internal NAD(P)H dehydrogenases in plant mitochondria
(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.
(Less)
- author
- Rasmusson, A. G. LU and Moller, I. M.
- organization
- publishing date
- 1991
- 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
- pmid:1722151
- 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
- 2024-01-04 07:46:27
@article{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 = {{Wiley-Blackwell}}, 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}}, doi = {{10.1111/j.1432-1033.1991.tb16415.x}}, volume = {{202}}, year = {{1991}}, }