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Inside-out submitochondrial particles from both potato tubers and pea leaves catalyze the transfer of hydride equivalents from NADPH to NAD+ as monitored with a substrate-regenerating system. The NAD+ analogue acetylpyridine adenine dinucleotide is also reduced by NADPH and incomplete inhibition by the complex I inhibitor diphenyleneiodonium (DPI) indicates that two enzymes are involved in this re
Two different cDNAs, homologous to genes for rotenone-insensitive NADH dehydrogenases of bacteria and yeast, were isolated from potato. The encoded proteins, called NDA and NDB, have calculated molecular masses of 55 and 65kDa, respectively. The N-terminal parts show similarity to mitochondrial targeting peptides and the polypeptides are in vitro imported into potato mitochondria. Import processin
Respiratory complex I of plant mitochondria has to date been investigated with respect to physiological function, biochemical properties and molecular structure. In the respiratory chain complex I is the major entry gate for low potential electrons from matrix NADH, reducing ubiquinone and utilizing the released energy to pump protons across the inner membrane. Plant complex I is active against a
Genes encoding subunits of complex I (EC 1.6.5.3) of the mitochondrial respiratory chain vary in their locations between the mitochondrial and nuclear genomes in different organisms, whereas genes for a homologous multisubunit complex in chloroplasts have to date only been found on the plastid genome. In potato (Solanum tuberosum L.), the gene coding for the mitochondrial 76 kDa iron-sulphur prote
Many diverse metabolic processes are coupled to the turnover of the coenzyme NADP in the matrix of plant mitochondria. NADPH can be produced via the NADP-specific isocitrate dehydrogenase as well as via enzymes like NAD-malic enzyme, NAD-malate dehydrogenase and Δ1-pyrroline-5-carboxylate dehydrogenase. Although not NADP-specific, the latter enzymes can all catalyse the reduction of NADP+ at appre
Mitochondrial respiratory chain complex I is a large multi-subunit enzyme composed of both organellar and nuclear encoded proteins. To investigate the role of the nuclear encoded components, expression of the gene for the 55 kDa NADH-binding subunit of complex I was disturbed by antisense repression in transgenic potato plants. The antisense construct driven by the CaMV 35S promoter decreases the
Progress in understanding the role of NAD(P)H oxidation in plant respiration is restricted by the lack of access to specific inhibitors of each of the unknown number of NAD(P)H dehydrogenases in the inner mitochondrial membrane. Platanetin (3,5,7,8-tetrahydroxy-6-isoprenyl flavone) is known to be an inhibitor of external NADH oxidation by plant mitochondria, while 7-iodo-acridone-4-carboxylic acid
In higher plants, genes for subunits of respiratory chain complex I (NADH:ubiquinone oxidoreductase) have so far been identified solely in organellar genomes. At least nine subunits are encoded by the mitochondrial DNA and 11 homologues by the plastid DNA. One of the 'key' components of complex I is the subunit binding the substrate NADH. The corresponding gene for the mitochondrial subunit has no
The addition of ubiquinone-1 (UQ-1) induced Ca2+-independent oxidation of deamino-NADH and NADH by intact potato (Solanum tuberosum L. cv Bintje) tuber mitochondria. The induced oxidation was coupled to the generation of a membrane potential. Measurements of NAD+-malate dehydrogenase activity indicated that the permeability of the inner mitochondrial membrane to NADH and deamino-NADH was not alter
Complex 1 of the respirator) chain (EC 1.6.531, measured as NADH-duroquinone and NADH-ubiquinone, reductase activities, was isolated from purified red beetroot (Beta vulgaris L.I mitochondria. The mitochondria were disrupted by freeze-thawing and inner membrane vesicles were pelleted. After solubilization of the vesicles with Triton X-100, the enzyme complex was purified 11-fold (compared to the a
Plant (and fungal) mitochondria contain multiple NAD(P)H dehydrogenases in the inner membrane all of which are connected to the respiratory chain via ubiquinone. On the outer surface, facing the intermembrane space and the cytoplasm, NADH and NADPH are oxidized by what is probably a single low-molecular-weight, nonproton-pumping, unspecific rotenone-insensitive NAD(P)H dehydrogenase. Exogenous NAD
The soluble fraction of disrupted red beetroot mitochondria was resolved by anion-exchange chromatography. Three NADH-oxidising activities were found, including one duroquinone reductase oxidising both NADH and NADPH. This NAD(P)H-duroquinone reductase, which we assign as the internal rotenone-insensitive NAD(P)H dehydrogenase, was further purified by affinity chromatography into a 26 kDa polypept
Purified mitochondria isolated from potato (Solanum tuberosum L. cv. Bintje) tuber, Jerusalem artichoke (Helianthus tuberosu L.) tuber and rat liver were disrupted at different pH and different EDTA and MgCl2 concentrations either by French Press treatment or by sonication. The submitochondrial particles (SMP) were isolated by differential centrifugation and polarity estimated by the latency of cy
Mitochondria were isolated from fresh beetroots (Beta vulgaris L. cvs Rubria and Nina) by differential centrifugation followed by Percoll gradient centrifugation. These purified mitochondria oxidized external NADH, although relatively slowly (20-40 versus 100-120 nanomoles oxygen per minute times milligram protein for NADH and succinate oxidation, respectively), with respiratory control ratios of
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
In mitoplasts from Arum maculatum spadices, succinate dehydrogenase (EC 1.3.99.1) and the alternative, cyanide-resistant oxidase activity (measured as m-chlorobenzhydroxamic acid-sensitive duroquinol oxidation) was unaffected by treatment with trypsin. In contrast, when 85% inside-out submitochondrial particles were treated with trypsin the alternative oxidase activity was inhibited by about 50% a
Purified potato tuber (Solanum tuberosum L. cv Bintje) mitochondria contain soluble, highly latent NAD+- and NADP+-isocitrate dehydrogenases, NAD+- and NADP+-malate dehydrogenases, as well as an NADPH-specific glutathione reductase (160, 25, 7200, 160, and 16 nanomoles NAD(P)H per minute and milligram protein, respectively). The two isocitrate dehydrogenase activities, but not the two malate dehyd
