Azide uncoupling

Oxidative phosphorylation DNP, potassium cyanide Antimycin A Sodium azide Formaldehyde Uncouples the oxidative phosphorylation from electron transport Acts at cytochrome oxidase B 7 Decreases the mitochondrial membrane potential 105 101,102 93,101,102... 

Intensity, but In fact parallels the appearance of the g 1.86 EPR signal which Is associated with the small fraction of uncoupled T3 sites (Figure 11, right). Thus, no low temperature MCD Intensity Is associated with the Intense 400 nm absorption band and It must be associated with azide binding to the antlferromagnetlcally coupled T3 site. 

In the mammal, complex polysaccharides which are susceptible to such treatment, are hydrolyzed by successive exposure to the amylase of the saliva, the acid of the stomach, and the disaccharidases (e.g., maltase, invertase, amylase, etc.) by exposure to juices of the small intestine. The last mechanism is very important. Absorption of the resulting monosaccharides occurs primarily in the upper part of the small intestine, from which the sugars are earned to the liver by the portal system. The absorption across die intestinal mucosa occurs by a combination of active transport and diffusion. For glucose, the aclive transport mechanism appears to involve phosphorylation The details are not yet fully understood. Agents which inhibit respiration (e.g., azide, fluoracetic acid, etc.) and phosphorylation (e.g., phlorizin), and those which uncouple oxidation from phosphorylation (e.g., dinitrophenol) interfere with the absorption of glucose. See also Phosphorylation (Oxidative). Once the various monosaccharides pass dirough the mucosa, interconversion of the other... 

Fig. 10.6. The effect of respiration and membrane potential (Ai )) on Cl permeation in brown adipose tissue mitochondria. When brown fat mitochondria were incubated in KCl in the presence of the ionophore, nigericin, they swelled (A, B). If a respiratory substrate (here G-3-P glycerol-3-phosphate) was added to the expanded mitochondria, they contracted, and this contraction ceased immediately and swelling was reintroduced if azide (NaNj) and an uncoupler (FCCP) were added (Fig. A). The passive halide ion permeability can be inhibited by GDP (cf.. Fig. 10.5), but respiration-driven contraction in KCl-expanded mitochondria was only partially inhibited by the presence of GDP (Fig. B) if again azide and uncoupler were added during the contraction, the mitochondria did not swell, indicating that the thermogenin channel was closed by GDP. This behaviour can partly be explained by the fact that the Cl permeation is driven by the membrane potential. Indeed, when, under similar conditions, the rate of contraction was plotted as a function of the membrane potential, it was seen that the rate was membrane potential dependent. It should, however, he noted that at low membrane potentials GDP nearly totally abolished the Cl permeation but when the membrane potential was increased above 30 mV, the inhibitory effect of GDP was apparently partially lost. The basis for this phenomenon is not understood it is not even known if there is a lower affinity of thermogenin for GDP in the energized membrane, as measurements of GDP affinities always refer to the non-energized situation. (Adapted from Nicholls et al. [27] (A, B) and Nicholls [94] (C).)...

Findings from a study done on acid-adapted Salmonella to lactic acid rinses from artificially inoculated beef muscle slices showed that acid-adapted strains were not any more resistant to acid decontamination than parental strains (Dickson and Kunduru, 1995). In a study done by Steiner and Sauer (2003), the overexpression of the ATP-dependent heli-case RecG was found to increase resistance to weak organic acids in E. coli. This was achieved by reduction of the toxic effects of the organic acids, reduction of the effects of the synthetic uncouplers (CCCP and DNP), and a reduction of the ATPase and cytochrome c inhibitor azide as a result of a decrease in pH or available ATP. In LAB, resistance mechanisms to... 

The dehydration of (/ )-2-hydroxyglutarate to glutaconate has been studied by Buckel and co-workers (229, 2S0), who have found that the syn elimination of ( )-2-hydroxyglutarate requires a prior activation of the enzyme from cell-free extracts of A. fermentans by ATP, NADH, and MgCl2. The enzymic reaction requires a dithiol, acetyl phosphate, and CoASH, as well as strictly anaerobic conditions, because the active enzyme is irreversibly inactivated on contact with oxygen. Evidence was presented that the adenylation of the protein may be a requisite for activation. Based on preliminary EPR studies and the inactivation of the enzymic reaction by hydroxylamine and uncouplers of oxidative phosphorylation (such as azide, arsenate, and 2,4-dinitrophenol), Schweiger and Buckel postulated a radical mechanism for 2-hydroxyglutarate dehydration via the hydroxyl radical (Scheme 53) (229). Hence, the ATP/NADH-dependent ac-... 

When they further observed that the normal nucleus contains a high proportion of mono-, di-, and trinucleotides of adenine, they claimed to have provided direct proof of their theory by demonstrating that the mono-or dinucleotides in the nucleus may be converted to ATP when oxygen is present. (The nucleotides can be extracted from the nucleus with acetate buffer at pH 5.1.) This conversion certainly suggested the existence of an intranuclear process of oxidative phosphorylation. As in mitochondria, oxidative phosphorylation in the nucleus is inhibited by uncouplers or agents blocking the electron transport chain. Nuclear oxidative phosphorylation is blocked by cyanide, azide, and antimycin A, or by dinitrophenol but, in contrast to mitochondria, it is resistant to Janus green, methylene blue, carbon monoxide, Dicumarol, and calcium. 

That the active concentration of iodide in the thyroid is energy dependent is suggested by several observations. The active concentration of iodide requires oxygen. It is blocked by metabolic poisons, such as cyanide and azides. There is a correlation between concentration ability and rate of oxidative phosphorylation. Uncouplers such as 2,4-dinitrophenol block iodine uptake in the thyroid. 

Phosphoric-carboxylic anhydride, see Carboxylic-phosphoric anhydride Phosphorus tribromide, 39 Phosphorylase b, 241, 293, 310-318 activation, 293 Phosphorylation cd nucleosides, 324,325 oxidative, uncoupling, 83 Phosphoryl azide, 78 Phosphorylazide diesters, 87 of-Phosphoryl nitrenes, 78... 

Cyanide, azide or carbon monoxide, all of which bind irreversibly to the iron of cytochrome a, and thus inhibit complex IV Again these compounds inhibit oxidation of malate and succinate, as both rely on cytochrome oxidase, and again the addition of the uncoupler has no effect. 

Substances such as 2,4-dinitrophenol, azide, gramicidin, and arsenite, which uncouple phosphorylation from oxidation, inhibit the oxidation of fatty acidsbut not of the primer itself. Lehninger and his co-workers showed that the oxidation of the reduced form of the codehydrogenase, DPNH or reduced DPN, caused oxidative phosphorylation. Thus, the oxidation of a tricarboxylic acid intermediate was not obligatory for fatty acid activation. As might be expected, therefore, fatty acid breakdown was initiated by the oxidation of DPNH in the absence of tricarboxlic acid cycle intermediates. The absence of tricarboxylic acid cycle inter-... 

The following paths of bacterial metabolism of glutamic acid have now been demonstrated and some at least (marked ) are inhibited by crystal violet or one of the uncoupling agents such as sodium azide or 2,4-dinitrophenol ... 

Table X shows the inhibitory action of sodium azide and 2,4-dinitro-phenol on the accumulation of free glutamic acid within Slaph. aureus incubated with some of the derivatives listed in Table IX. In general all the systems studied are sensitive to the action of these uncoupling agents and no one system is markedly less sensitive than the others. This may mean that the accumulation process in all cases, even with diethylglutamic ester as source, involves some coupled metabolism.

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