antimycin and salicylhydroxamic-acid

Hyoscyamus albus hairy roots secrete riboflavin under Fe-deficient conditions. To determine whether this secretion was linked to an enhancement of respiration, both riboflavin secretion and the reduction of 2,3,5-triphenyltetrazolium chloride (TTC), as a measure of respiration activity, were determined in hairy roots cultured under Fe-deficient and Fe-replete conditions, with or without aeration. Appreciable TTC-reducing activity was detected at the root tips, at the bases of lateral roots and in internal tissues, notably the vascular system. TTC-reducing activity increased under Fe deficiency and this increase occurred in concert with riboflavin secretion and was more apparent under aeration. Riboflavin secretion was not apparent under Fe-replete conditions. In order to examine which elements of the mitochondrial electron transport chain might be involved, the effects of the respiratory inhibitors, barbiturate, dicoumarol, malonic acid, antimycin, KCN and salicylhydroxamic acid (SHAM) were investigated. Under Fe-deficient conditions, malonic acid affected neither root growth, TTC-reducing activity nor riboflavin secretion, whereas barbiturate and SHAM inhibited only root growth and TTC-reducing activity, respectively, and the other compounds variously inhibited growth and TTC-reducing activity. Riboflavin secretion was decreased, in concert with TTC-reducing activity, by dicoumarol, antimycin and KCN, but not by SHAM. In Fe-replete roots, all inhibitors which reduced riboflavin secretion in Fe-deficient roots showed somewhat different effects: notably, antimycin and KCN did not significantly inhibit TTC-reducing activity and the inhibition by dicoumarol was much weaker in Fe-replete roots. Combined treatment with KCN and SHAM also revealed that Fe-deficient and Fe-replete roots reduced TTC in different ways. A decrease in the Fe content of mitochondria in Fe-deficient roots was confirmed. Overall, the results suggest that, under conditions of Fe deficiency in H. albus hairy roots, the alternative NAD(P)H dehydrogenases, complex III and complex IV, but not the alternative oxidase, are actively involved both in respiration and in riboflavin secretion.

Topics: Antimycin A; Barbiturates; Cyanates; Dicumarol; Electron Transport; Hyoscyamus; Iron Deficiencies; Malonates; Plant Roots; Riboflavin; Salicylamides

This article describes the first detailed analysis of mitochondrial electron transfer and oxidative phosphorylation in the pathogenic filamentous fungus, Gaeumannomyces graminis var. tritici. While oxygen consumption was cyanide insensitive, inhibition occurred following treatment with complex III inhibitors and the alternative oxidase inhibitor, salicylhydroxamic acid (SHAM). Similarly, maintenance of a Deltapsi across the mitochondrial inner membrane was unaffected by cyanide but sensitive to antimycin A and SHAM when succinate was added as the respiratory substrate. As a result, ATP synthesis through complex V was demonstrated to be sensitive to these two inhibitors but not to cyanide. Analysis of the cytochrome content of mitochondria indicated the presence of those cytochromes normally associated with electron transport in eukaryotic mitochondria together with a third, b-type heme, exhibiting a dithionite-reduced absorbance maxima at 560 nm and not associated with complex III. Antibodies raised to plant alternative oxidase detected the presence of both the monomeric and dimeric forms of this oxidase. Overall this study demonstrates that a novel respiratory chain utilizing the terminal oxidases, cytochrome c oxidase and alternative oxidase, are present and constitutively active in electron transfer in G. graminis tritici. These results are discussed in relation to current understanding of fungal electron transfer and to the possible contribution of alternative redox centers in ATP synthesis.

Topics: Antifungal Agents; Antimycin A; Ascomycota; Carboxin; Cytochromes; Electron Transport; Microbial Sensitivity Tests; Oligomycins; Oxygen Consumption; Potassium Cyanide; Salicylamides; Triticum

Sulfide is oxidized in the mitochondria of the lugworm Arenicola marina. Mitochondrial sulfide oxidation is coupled with oxygen consumption and with an equimolar production of thiosulfate [Völkel, S. & Grieshaber, M. K. (1994) Mar. Biol. 118, 137-147]. Mitochondrial respiration in the presence of malate (or succinate) and ADP but without sulfide could be completely inhibited by rotenone, antimycin, cyanide, and sulfide. Only 40% inhibition was achieved by salicylhydroxamic acid. Sulfide oxidation (with sulfide as the only substrate) was fully inhibited by antimycin and by salicylhydroxamic acid but not by rotenone or sulfide. Moreover, sulfide oxidation was 3-4-fold less sensitive to cyanide as compared to normal respiration. The data indicate that sulfide oxidation in A. marina is linked to the respiratory electron transport chain. We suggest that electrons from sulfide enter the respiratory chain via ubiquinone or at the ubiquinol-cytochrome-c oxidoreductase. At sulfide concentrations higher than 10 microM, the cytochrome-c oxidase is blocked and electrons from sulfide are transferred to oxygen via an alternative terminal oxidase.

Topics: Animals; Antimycin A; Cyanides; Electron Transport; Electron Transport Complex III; Mitochondria; NAD(P)H Dehydrogenase (Quinone); Oxidation-Reduction; Oxidoreductases; Oxygen Consumption; Polychaeta; Rotenone; Salicylamides; Sulfides; Thiosulfates; Uncoupling Agents

Inhibition analysis of respiration of Leishmania donovani promastigotes in resting, starved and permeabilized cells in the presence of classical electron transfer complex inhibitors such as rotenone, thenoyltrifluoroacetone and antimycin demonstrated the absence of complex I component of the respiratory chain in this organism. Cyanide failed to completely block the oxygen uptake (residual 25-30%) even at high concentrations. The alternative oxidase inhibitor for Trypanosoma brucei, salicylhydroxamic acid (SHAM) had no effect on respiration while the cytochrome o inhibitor orthohydroxydiphenyl (OHD) could block cyanide-insensitive respiration at low concentrations. Succinate-dependent O2 uptake in permeabilized cells follows the classical pathway. Oxidation of NADH by a membrane-rich fraction produced H2O2 as the end product and was insensitive to respiratory chain inhibitors. The presence of NADH-fumarate reductase was demonstrated in membrane-rich fraction and fumarate could reduce H2O2 production from NADH indicating fumarate to be an endogenous substrate for accepting electrons from NADH. A differential route for NADH oxidation was further confirmed by NADH cytochrome c reductase insensitivity to antimycin. A tentative scheme for electron transfer pathway in this organism is proposed in which a reversal of Krebs cycle enzymes occur producing succinate that can be excreted or oxidized depending upon the energy demands of the cell. Inhibition studies also suggest bifurcations of the respiratory chain that can be of minor importance for the organism.

Topics: Animals; Antimycin A; Antiprotozoal Agents; Cell Membrane Permeability; Cyanides; Dose-Response Relationship, Drug; Electron Transport; Enzyme Inhibitors; Kinetics; Leishmania donovani; Models, Biological; NAD; Oxidation-Reduction; Oxygen Consumption; Rotenone; Salicylamides

Bloodforms of Trypanosoma brucei brucei (STIB 247) differentiated in vitro into procyclic forms as described in the accompanying paper (Markos et al. 1989). The importance of the respiratory chain for the process was tested by the inhibition of its development (omission of hemin from the medium) or function (respiratory inhibitors). In the absence of hemin, all enzyme markers of the procyclic state, except for hemoproteins, developed to 50-70 per cent of control values. The presence of hemin is therefore not essential for the onset of differentiation, although the process cannot be completed under hemin limitation. Addition of 1 mumole.dm-3 KCN, 10 mumole.dm-3 antimycin A, or 100 mumole.dm-3 salicyl hydroxamate (SHAM) did not block the differentiation, although it proceeded at a slower rate. The development of the inner mitochondrial membrane markers--succinate: cytochrome c reductase, and NADH: cytochrome c reductase--was strongly inhibited by KCN or antimycin. None of these inhibitors had a significant effect on the activity of procyclic state marker--glycosomal malate dehydrogenase.

Topics: Animals; Antimycin A; Culture Media; Hemin; Malate Dehydrogenase; NADH Dehydrogenase; Oxygen Consumption; Potassium Cyanide; Salicylamides; Succinate Cytochrome c Oxidoreductase; Trypanocidal Agents; Trypanosoma brucei brucei