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PubMed1977

Energy transduction and adenine nucleotides in mitochondria from rat liver after hypoxic perfusion.

The characteristics of mitochondria isolated from perfused livers of rats under hypoxic or oxic conditions were studied. The electron transfer activity was about 60% of normal after hypoxic perfusion for 3 h, but respiratory control was abolished almost completely. These parameters recovered considerably on subsequent oxic perfusion. The adenine nucleotide contents and their net uptake decreased in hypoxia, closely correlated with the energy transduction. Energy-dependent nicotinamide nucleotide transhydrogenase activity and NAD reduction by succinate in submitochondrial particles were most severely inhibited after hypoxic perfusion and were also correlated with adenine nucleotide contents in the particles. These results are discussed in terms of the involvement of adenine nucleotides in energy-transducing systems in mitochondrial membranes.

Adenosine Diphosphate↗
PubMed1981

Studies on the uptake of [3H]dopamine by synaptic vesicle fraction isolated from bovine brain.

1. A synaptic vesicle fraction isolated from bovine caudatolenticular nuclei showed enzymic activities of tyrosine hydroxylase [EC 1.14.16.2] and dopamine beta-hydroxylase [EC 1.14.17.1]. Tyrosine hydroxylase, whose subcellular localization is uncertain, appeared to be associated with the synaptic vesicles. 2. The vesicle fraction took up [3H]dopamine increasingly with time without the aid of ATP (6.3 pmol of [3H]dopamine per mg of vesicle proteins, or 3-4% of the added dopamine, at 30 min). In the presence of ATP, a transient accumulation of the amine was observed, reaching the highest level at 7-10 min (5.6 pmol dopamine/mg protein), and then a rapid release of the amine took place, obeying first-order kinetics with respect to the amine concentration. The amine uptake was strongly inhibited with NEM, regardless of the presence or absence of ATP. 3. The vesicle fraction also exhibited a weak ability to translocate protons inward and ATP-dependently, as monitored by an increase in the fluorescence intensity of ANS. The fluorescence enhancement persisted for at least 30 min and this time-dependent change was not consistent with that of the transient accumulation of [3H]dopamine mentioned above. Since the present vesicle preparation contained a small amount of mitochondrial ATPase (18-20% of the total activity), the proton translocating ability could be attributable to contaminating submitochondrial particles. 4. Therefore these results made it impossible to conclude that the transient uptake of [3H]dopamine by the synaptic vesicles was coupled to ATP hydrolysis.

Adenosine Diphosphate↗
PubMed1983

Detrimental effects of methyl hydroperoxy-epoxy-octadecenoate on mitochondrial respiration: detoxication by rat liver mitochondria.

Methyl hydroperoxy-epoxy-octadecenoate (ML-X) inhibited state 3 respiration of rat heart and liver mitochondria with glutamate and malate as substrates. It also inhibited the NADH oxidase and NADH-ubiquinone-1 reductase activities of rat heart and liver submitochondrial particles (SMP). In liver mitochondria and SMP, these inhibitory effects of ML-X were transient, whereas in heart mitochondria and SMP, recovery of the respiratory activities did not occur. Results from high pressure liquid chromatography and 13C-NMR studies indicated that ML-X was converted to hydroperoxy-epoxy-octadecenoic acid (L-X) by incubation with liver mitochondria or SMP but not with heart mitochondria. Purified L-X apparently inhibited state 3 respiration of heart and liver mitochondria with glutamate and malate as substrates, but the amount required for 50% inhibition was 2-3 times larger than that of ML-X. Heart mitochondria adsorbed 36% of the added ML-X, while only 10% of the added L-X was adsorbed. These findings suggest that the recovery of the ML-X-inhibited respiratory activities of liver mitochondria and SMP occurs by conversion of ML-X to L-X, which is only weakly adsorbable on the mitochondrial membrane.

Adsorption↗
PubMed1983

Kinetics of superoxide formation by respiratory chain NADH- dehydrogenase of bovine heart mitochondria.

Formation of superoxide anions (O2-) by bovine heart NADH-dehydrogenase preparation (Complex I) supported by an NADH- or NADPH-generating system was studied kinetically. Both NADH- and NADPH-dependent superoxide-forming activities of Complex I were biphasic in double reciprocal plots. The NADH-dependent reaction had two sets of kinetic parameters: One Km value for NADH was 10 times higher than the other one, and the Vmax of the reaction with high Km was about 4 times higher than that of the reaction with low Km. Similar Vmax values were obtained for the NADPH-dependent reactions but the Km values were a thousand times higher than those of the NADH-dependent reactions. The plots of the NADH-dependent activity of rotenone-treated submitochondrial particles were also biphasic. The double reciprocal plots of NADH- and NADPH-dependent 2,6-dichlorophenolindophenol (DCIP) reductase activities of Complex I were linear and the plots of the superoxide-forming activities against the DCIP reductase activities were biphasic. These results indicate that the biphasic double reciprocal plots of the superoxide-forming activities against reduced coenzymes are not caused by interaction between reduced coenzymes and the NADH-dehydrogenase but are due to the presence of at least two superoxide-forming sites in the respiratory chain NADH-dehydrogenase.

Animals↗
PubMed1995

Isoproterenol-dependent decrease in oxygen uptake and respiratory enzyme activities in rat myocardial tissue and mitochondria.

OBJECTIVE: Myocardial damage induced by isoproterenol is believed to be secondary to increased oxygen demands on the heart. Our objective was to test an additional primary action of isoproterenol on tissue and mitochondrial oxidative metabolism and to compare these effects with the effects of other adrenergic agents in the presence of adrenergic inhibitors. DESIGN: Prospective, dose-response study. SETTING: Research laboratory at a university hospital. SUBJECTS: Fifty Sprague-Dawley female rats (200 to 350 g), slightly anesthetized with ether and divided into several groups. INTERVENTIONS: In 26 rats, the heart was removed, cut into fine slices (0.5-mm thickness), and placed in an ice-cold buffer. In 22 animals, the hearts were perfused in the Langendorff manner and chopped and processed for mitochondrial studies. MEASUREMENTS AND MAIN RESULTS: We determined the following: a) the direct "in vitro" effects of isoproterenol and related catecholamines on normal oxygen uptake using myocardial slices; b) rat heart oxygen consumption and mitochondrial oxygen uptake from isolated organs, perfused with isoproterenol; c) measurements of enzyme activities in submitochondrial particles from the same perfused hearts; and d) the direct effects of isoproterenol on normal mitochondria isolated from normal nonperfused hearts. The oxygen uptake was determined polarographically with a Clark-type electrode and enzymatic activities were assayed by spectrophotometric reduction of cytochrome c at 550 nm with different mitochondrial substrates. Isoproterenol (0.01 to 100 nM) decreased the oxygen uptake by the heart slices in a dose-dependent manner. In comparison, epinephrine or norepinephrine per se did not change the parameter. However, with the addition of alpha-adrenergic receptor inhibitors, oxygen uptake decreased to values similar to those values obtained with isoproterenol. Also, mitochondria isolated from hearts perfused with isoproterenol had decreased state 3 respiratory rates (by 50%) and decreased respiratory control ratios (by 30%), without changes in adenosine 5'-diphosphate/oxygen ratios. The respiratory chain enzyme activities were also lowered. CONCLUSIONS: The data suggest that while isoproterenol increases "in vivo" oxygen uptake by the working rat heart, isoproterenol can simultaneously decrease maximal adenosine 5'-diphosphate-induced mitochondrial oxygen uptake and in vitro myocardial tissue oxygen uptake, probably by modifying the mitochondrial respiratory enzymes. This action could be counteracted by alpha-adrenergic agonist effects.

Animals↗
PubMed2002

Long-term angiotensin II inhibition increases mitochondrial nitric oxide synthase and not antioxidant enzyme activities in rat heart.

OBJECTIVE: To provide insight into the subcellular mechanisms involved in the improvement of cardiovascular structure and function by long-term inhibition of the renin-angiotensin system. DESIGN: The activities of antioxidant enzymes and mitochondrial free radical production were determined in the heart of control (C), enalapril-treated (E), and losartan-treated (L) rats to test the hypothesis of increased antioxidant enzyme activities and participation of mitochondria in the effects of chronic treatments with angiotensin II inhibitors. METHODS: At 6 and 18 months of treatment, superoxide dismutases (SOD), Se-glutathione peroxidase, and catalase activities were determined in left ventricle homogenates by spectrophotometric methods and nitric oxide (NO) production in submitochondrial membranes by the oxyhemoglobin oxidation assay. The maximal rate of hydrogen peroxide (H2O2) production by submitochondrial membranes was also evaluated at 18 months by the scopoletin-horseradish peroxidase method. RESULTS: No significant increase was found in the antioxidant enzymes measured. At 6 months, Mn-SOD was actually decreased in E and catalase in both E and L, whereas at 18 months Se-glutathione peroxidase was decreased in L. Production of NO by submitochondrial particles was 64% higher at 6 months in E and 105% higher at 18 months in E and L. Maximal hydrogen peroxide production was lower at 18 months in both groups. CONCLUSIONS: Results do not support the hypothesis of an increase in antioxidant enzyme activity by long-term treatment with angiotensin II inhibitors as previously suggested and point towards a role for the NO produced by mitochondrial nitric oxide synthase (mtNOS) in the protective effect of these drugs.

Angiotensin II↗
PubMed1991

Molecular damage to rat liver mitochondrial H(+)-ATPase during cold preservation with UW solution.

Deterioration of rat liver mitochondrial function during cold preservation with UW solution was studied. Mitochondria were isolated from control liver (0-hr preservation), 24-hr preserved liver, and 48-hr preserved liver with UW solution at 4 degrees C. Respiration assay revealed that phosphorylation was damaged more rapidly than oxidation. Inside-out submitochondrial particles prepared from each sample by sonication in the presence of EDTA were subjected to ATPase assay. ATP hydrolyzing activity of H(+)-ATPase (ATP synthase), which plays a key role in phosphorylation in mitochondria, decreased markedly to 58% after 24-hr preservation. After 48-hr preservation, reduction to 40% of control was noted. When an intrinsic H(+)-ATPase inhibitor protein was removed from ESMP by Sephadex gel filtration, decrease of the ATPase activity was enhanced down to 49% and 29% of the control for 24-hr and 48-hr preserved liver, respectively. Molecular damage of the enzyme was confirmed by SDS-PAGE. Alpha subunit of the enzyme decreased time-dependently, and H(+)-ATPase molecules that lost alpha subunit seemed to lose their catalytic activity. Although the cause of the molecular damage of H(+)-ATPase is not clear yet, some mitochondrial protease(s) may be involved.

Adenosine↗
PubMed1992

Effects of deuterium oxide on growth, proton extrusion, potassium influx, and in vitro plasma membrane activities in maize root segments.

Elongation of subapical segments of maize (Zea mays) roots was greatly inhibited by (2)H(2)O in the incubation medium. Short-term exposure (30 min) to (2)H(2)O slightly reduced O(2) uptake and significantly increased ATP levels. (2)H(2)O inhibited H(+) extrusion in the presence of both low (0.05 mm) and high (5 mm) external concentrations of K(+) (about 30 and 53%, respectively at 50% [v/v] (2)H(2)O). Experiments on plasma membrane vesicles showed that H(+)-pumping and ATPase activities were greatly inhibited by (2)H(2)O (about 35% at 50% [v/v] (2)H(2)O); NADH-ferricyanide reductase and 1,3-beta-glucan synthase activities were inhibited to a lesser extent (less than 15%). ATPase activities present in both the tonoplast-enriched and submitochondrial particle preparations were not affected by (2)H(2)O. Therefore, the effect of short incubation time and low concentration of (2)H(2)O is not due to a general action on overall cell metabolism but involves a specific inhibition of the plasma membrane H(+) -ATPase. K(+) uptake was inhibited by (2)H(2)O only when K(+) was present at a low (0.05 mm) external concentration where absorption is against its electrochemical potential. The transmembrane electric potential difference (E(m)) was slightly hyperpolarized by (2)H(2)O at low K(+), but was not affected at the higher K(+) concentrations. These results suggest a relationship between H(+) extrusion and K(+) uptake at low K(+) external concentration.

Journal Article↗
PubMed1996

Ubiquinone-1 Induces External Deamino-NADH Oxidation in Potato Tuber Mitochondria.

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 altered by the addition of UQ-1. We conclude that UQ-1-induced external deamino-NADH oxidation is due to a change in specificity of the external rotenone-insensitive NADH dehydrogenase. The addition of UQ-1 also induced rotenone-insensitive oxidation of deamino-NADH by inside-out submitochondrial particles, but whether this was due to a change in the specificity of the internal rotenone-insensitive NAD(P)H dehydrogenase or to a bypass in complex I could not be determined.

Journal Article↗
PubMed1998

Role of the ascorbate-glutathione cycle of mitochondria and peroxisomes in the senescence of pea leaves

We investigated the relationship between H2O2 metabolism and the senescence process using soluble fractions, mitochondria, and peroxisomes from senescent pea (Pisum sativum L.) leaves. After 11 d of senescence the activities of Mn-superoxide dismutase, dehydroascorbate reductase (DHAR), and glutathione reductase (GR) present in the matrix, and ascorbate peroxidase (APX) and monodehydroascorbate reductase (MDHAR) activities localized in the mitochondrial membrane, were all substantially decreased in mitochondria. The mitochondrial ascorbate and dehydroascorbate pools were reduced, whereas the oxidized glutathione levels were maintained. In senescent leaves the H2O2 content in isolated mitochondria and the NADH- and succinate-dependent production of superoxide (O2.-) radicals by submitochondrial particles increased significantly. However, in peroxisomes from senescent leaves both membrane-bound APX and MDHAR activities were reduced. In the matrix the DHAR activity was enhanced and the GR activity remained unchanged. As a result of senescence, the reduced and the oxidized glutathione pools were considerably increased in peroxisomes. A large increase in the glutathione pool and DHAR activity were also found in soluble fractions of senescent pea leaves, together with a decrease in GR, APX, and MDHAR activities. The differential response to senescence of the mitochondrial and peroxisomal ascorbate-glutathione cycle suggests that mitochondria could be affected by oxidative damage earlier than peroxisomes, which may participate in the cellular oxidative mechanism of leaf senescence longer than mitochondria.

Journal Article↗
PubMed1971

Specific inhibition of the cyanide-insensitive respiratory pathway in plant mitochondria by hydroxamic acids.

Hydroxamic acids, R-CONHOH, are inhibitors specific to the respiratory pathway through the alternate, cyanide-insensitive terminal oxidase of plant mitochondria. The nature of the R group in these compounds affects the concentration at which the hydroxamic acids are effective, but it appears that all hydroxamic acids inhibit if high enough concentrations are used. The benzhydroxamic acids are effective at relatively low concentrations; of these, the most effective are m-chlorobenzhydroxamic acid and m-iodobenzhydroxamic acid. The concentrations required for half-maximal inhibition of the alternate oxidase pathway in mung bean (Phaseolus aureus) mitochondria are 0.03 mm for m-chlorobenzhydroxamic acid and 0.02 mm for m-iodobenzhydroxamic acid. With skunk cabbage (Symplocarpus foetidus) mitochondria, the required concentrations are 0.16 for m-chlorobenzhydroxamic acid and 0.05 for m-iodobenzhydroxamic acid. At concentrations which inhibit completely the alternate oxidase pathway, these two compounds have no discernible effect on either the respiratory pathway through cytochrome oxidase, or on the energy coupling reactions of these mitochondria. These inhibitors make it possible to isolate the two respiratory pathways and study their mode of action separately. These inhibitors also enhance an electron paramagnetic resonance signal near g = 2 in anaerobic, submitochondrial particles from skunk cabbage, which appears to be specific to the alternate oxidase and thus provides a means for its assay.

Cyanides↗
PubMed1980

Oxidation of Reduced Nicotinamide Adenine Dinucleotide Phosphate by Potato Mitochondria: INHIBITION BY SULFHYDRYL REAGENTS.

Potato tuber mitochondria oxidized exogenous NADH and exogenous NADPH at similar rates; the electron transfer inhibitor rotenone did not inhibit the oxidation of either substrate. Submitochondrial particles, prepared from potato tuber mitochondria, exhibited a greater capacity to oxidize NADH than NADPH; rotenone inhibited the oxidation of NADH by 29% and the oxidation of NADPH by 16%. The oxidation of both NADH and NADPH by potato mitochondria exhibited pH optima of 6.8, and although substantial NADH oxidase activity was observed at pH 8.0, little NADPH oxidase activity was detected at that pH. The oxidation of NADPH by the mitochondria was more sensitive to inhibition by EDTA than was the oxidation of NADH.The sulfhydryl reagents N-ethylmaleimide, p-chloromercuribenzoate, p-chloromercuriphenyl sulfonic acid, and mersalyl inhibited the oxidation of exogenous NADPH by the mitochondria whereas NADH oxidation was unaffected at similar concentrations of inhibitor. The data suggest that exogenous NADPH is oxidized by potato mitochondria via a dehydrogenase primarily situated on the outer face of the inner mitochondrial membrane that is neither the dehydrogenase involved with endogenous NADH oxidation nor with exogenous NADH oxidation.

Journal Article↗
PubMed1981

Disulfiram inhibition of the alternative respiratory pathway in plant mitochondria.

Disulfiram (tetraethylthiuram disulfide) was found to be a potent and selective inhibitor of the alternative respiratory path of plant mitochondria. The onset of inhibition by disulfiram takes several minutes and the inhibition is not readily reversed by washing, nor by metal ions. By contrast, thiols such as dithiothreitol not only reverse, but also prevent, disulfiram inhibition. Inhibition by disulfiram and by hydroxamic acids are not mutually exclusive. Structural analogs of disulfiram are far less potent inhibitors, with the exception of bisethyl xanthogen. Inhibition is due to disulfiram, per se, and not to its reduction product, diethyldithiocarbamate, a powerful chelator. Accordingly, the inhibitory effect of disulfiram is considered to involve the formation of mixed disulfides with one or more sulfhydryl groups in the alternative path. Disulfiram does not act as an electron sink diverting electron flow from oxygen.Disulfiram inhibition was observed only with isolated mitochondria or submitochondrial particles. In intact cells or tissues either a failure to absorb disulfiram, or its dissipation in the cytosol, precludes inhibition. In vitro, bovine serum albumin reduces disulfiram inhibition by complexing free inhibitor.The binding of (35)S-disulfiram by cyanide-resistant mitochondria displays the same kinetics as disulfiram inhibition. A comparison was made of (35)S-disulfiram binding by cyanide-sensitive and cyanide-resistant potato mitochondria. Cyanide-resistant mitochondria were obtained from ethylene-treated potato tubers. Incorporation of label proved essentially the same in both types of mitochondria, suggesting that the disulfiram-sensitive component of the alternative path is present in untreated potato tubers, and is not induced by ethylene.

Journal Article↗
PubMed1982

Cytokinin modification of mitochondrial function.

6-Benzylaminopurine, 6-(Delta(2)-isopentenylamino)purine, 6-furfurylaminopurine, rotenone, and antimycin A inhibited oxidation of NADH by mitochondrial sonicates or submitochondrial particles (but not by intact mitochondria) from pea (Pisum sativum L., cult. Alaska) stems and mung bean (Vigna radiata L. Wilczak) hypocotyls. The above purine cytokinins can interfere with electron transport from NADH to the cytochrome system in the inner mitochondrial membrane. Adenine did not inhibit oxidation by sonicated mitochondria, and zeatin was almost ineffective. Zeatin scarcely inhibited state 3 malate respiration by intact mitochondria, but the O-formyl and O-n-propionyl esters of zeatin and the O-acetyl ester of 2-chlorozeatin were more active. Perhaps zeatin is ineffective because it does not get into the inner membranes of the isolated mitochondria, whereas the esters and other cytokinins mentioned above do. N-4-(2-chloropyridyl)-N'-Phenylurea, which has cytokinin-like effects on plant growth and development, inhibited NADH oxidation by sonicated mitochondria. It also inhibited malate, succinate, and NADH oxidation by intact mitochondria; in contrast, the latter two oxidations were not decreased by purine cytokinins.The benzyl, isopentenyl, and furfuryl aminopurines inhibited malate (but not succinate) oxidation by rat liver mitochondria, if ADP was present. In the absence of ADP, these cytokinins promoted succinate (but not malate) oxidation. Zeatin and adenine had slight, if any, effect in either situation.

Journal Article↗
PubMed1983

Solubilization and partial purification of n,n'-dicyclohexylcarbodiimide-sensitive ATPase from pea cotyledon mitochondria.

The N,N'-dicyclohexylcarbodiimide (DCCD)-sensitive ATPase of pea (Pisum sativum L.) cotyledon mitochondria was solubilized from submitochondrial particle membranes with sodium cholate and ammonium sulfate. Ammonium sulfate precipitation of the enzyme resulted in an increase in specific activity. At between 38% and 45% saturated ammonium sulfate, 20% of the ATPase activity was precipitated, with a specific activity 4 to 5 times higher than that of the crude enzyme. The precipitate was highly sensitive to DCCD.The properties of the ammonium sulfate preparation were investigated. It contained levels of cytochrome and NADH dehydrogenase contamination comparable to those of the highly purified F(0)F(1) preparations from animal tissue. The high degree of purification was corroborated by sodium dodecyl sulfate electrophoresis.

Journal Article↗
PubMed1985

Isolation and Antigenic Characterization of Corn Mitochondrial F(1)-ATPase.

Corn mitochondrial F(1)-ATPase was purified from submitochondrial particles by chloroform extraction. Enzyme stored in ammonium sulfate at 4 degrees C was substantially activated by ATP, while enzyme stored at -70 degrees C in 25% glycerol was not. Enzyme in glycerol remained fully active (8-9 micromoles P(i) released per minute per milligram), while the ammonium sulfate preparations steadily lost activity over a 2-month storage period. The enzyme was cold labile, and inactived by 4 minutes at 60 degrees C. Treatment with octylglucoside resulted in complete loss of activity, while vanadate had no effect on activity. The apparent subunit molecular weights of corn mitochondrial F(1)-ATPase were determined by SDS-polyacrylamide gel electrophoresis to be 58,000 (alpha), 55,000 (beta), 35,000 (gamma), 22,000 (delta), and 12,000 (epsilon). Monoclonal and polyclonal antibodies used in competitive binding assays demonstrated that corn mitochondrial F(1)-ATPase was antigenically distinct from the chloroplastic CF(1)-ATPases of corn and spinach. Monoclonal antibodies against antigenic sites on spinach CF(1)-ATPase beta and gamma subunits were used to demonstrate that those sites were either changed substantially or totally absent from the mitochondrial F(1)-ATPase.

Journal Article↗
PubMed1989

Reconstitution of Oxidative Phosphorylation and of Oligomycin-Sensitive ATPase by Five- and Six-Subunit Forms of Pea Mitochondrial F(1)-ATPase.

Five- and six-subunit forms of F(1)-ATPase were purified from pea (Pisum sativum L. cv Homesteader) cotyledon submitochondrial particles. Apart from the usual complement of five subunits, the six-subunit enzyme contained an additional 26,500-dalton protein. Both forms of the F(1)-ATPase were used to reconstitute oxidative phosphorylation in F(1)-depleted (ASU) as well as in F(1) and oligomycin-sensitivity conferring protein (OSCP)-depleted (ASUA) bovine mitochondrial membranes. The six-subunit enzyme was considerably more efficient in reconstituting the ATP synthesis than the five-subunit enzyme. Both forms of the enzyme were also able to reconstitute the ATPase activity in ASU- as well as in ASUA-particles. There were substantial differences, however, in the oligomycin sensitivity of the ATPase bound to the ASUA-particles: 20 and 60% inhibition by oligomycin was obtained in the case of the five-subunit and six-subunit enzyme, respectively. We conclude, that the 26,500-dalton protein present in the six-subunit F(1)-ATPase is responsible for the increase in oligomycin sensitivity of the bound enzyme and functions, therefore, as the plant OSCP.

Journal Article↗
PubMed1992

Partial Purification and Characterization of Complex I, NADH:Ubiquinone Reductase, from the Inner Membrane of Beetroot Mitochondria.

A NADH dehydrogenase was isolated from an inner membrane-enriched fraction of beetroot mitochondria (Beta vulgaris L.) by solubilization with sodium deoxycholate and purified using gel filtration and affinity chromatography. The NADH dehydrogenase preparation contained a minor ATPase contamination. Beetroot mitochondria were chosen as the isolation material for purifying the enzymes responsible for oxidizing matrix NADH due to the absence of the externally facing NADH dehydrogenase in the variety we have used. The purified NADH dehydrogenase complex catalyzed the reduction of various electron acceptors with NADH as the electron donor, was not sensitive to rotenone inhibition, and had a slow NADPH-ubiquinone 5 reductase activity. The isolated complex contained 14 major polypeptides. It was concluded that the dehydrogenase represented a form of the plant mitochondrial complex I and not the internally facing rotenone-insensitive NADH dehydrogenase found in plant mitochondria because of its complex structure, its cross-reactivity with antisera raised against bovine heart mitochondrial complex I, and the similarity of its kinetics and inhibitor responses to rotenone-sensitive NADH oxidation by beetroot submitochondrial particles.

Journal Article↗