Mitochondrial electron transport system

Other enzyme systems may also be directly or indirectly involved in the generation of ROS in the lung, including those of the eicosanoid pathway, the mitochondrial electron transport system, and aldehyde, glucose and xanthine oxidases (Parks and Granger, 1986). These systems may also be relevant to lung damage. For example, the oedematous pulmonary injury that results from cessation of blood flow for a period followed by reinstatement of... 

The desaturation process is particularly interesting as it provides an example of a microsomal (as opposed to mitochondrial) electron transport system. The enzymes responsible, fatty acyl-CoA desaturases, are examples of mixed function oxidases... 

Atovaquone is a naphthoquinone whose mechanism of action involves inhibition of the mitochondrial electron transport system in the protozoa. Malaria parasites depend on de novo pyrimidine biosynthesis through dihy-droorotate dehydrogenase coupled to electron transport. Plasmodia are unable to salvage and recycle pyrimidines as do mammalian cells. 

Mechanism of Action A systemic anti-infective that inhibits the mitochondrial electron-transport system at the cytochrome bcl complex (Complex 111), which interrupts nucleic acid and adenosine triphosphate synthesis. Therapeutic Effect Antiprotozoal and antipneumocystic activity. 

The reaction will proceed toward oxaloacetate formation in the cell if low product concentration is maintained. Oxidation of NADH by the mitochondrial electron transport system and utilization of oxaloacetate in the formation of citrate shifts the malate-oxaloacetate reaction toward oxaloacetate production. 

NADH-ubiquinone reductase was isolated by Hatefi et al. in 1961 (27-B9). A procedure was developed for the resolution of the mitochondrial electron transport system into four enzyme complexes. Recently, a fifth fraction, which is capable of energy conservation and ATP-Pi exchange, was also isolated (30, 31). The overall scheme for the isolation of the five component enzyme complexes of the mitochondrial electron transport-oxidative phosphorylation system is given in Fig. 1. It is seen... 

It has been shown recently that the mitochondrial electron transport system contains at least three different fe-type cytochromes 178). Two of these cytochromes are found in complex III, and under appropriate conditions are reducible with substrates. The third 6-type cytochrome was discovered by Davis et al. 178), and shown to fractionate exclusively into complex II. At 77°K, the cytochrome 6 of complex II exhibits a double a band at 557.5 and 550 nm, a prominent band at 531 nm, and a Soret band at 422 nm (Fig. 29). Cytochrome 6557.5 appears to have a low reduction potential. It is not detectably reduced by succinate in either complex II or respiratory particles, but its dithionite reduced form is rapidly oxidized by either fumarate or ubiquinone. The role of this cytochrome in mammalian mitochondria is not known. Davis et al. 178) have suggested that it might be an electron entry point for an unknown ancillary tributary of the respiratory chain. Further, Bruni and Racker 179) have shown that a preparation of cytochrome 6 is required for reconstitution of succinate-ubiquinone reductase activity (see below). 

Mitochondrial electron transport system Rotenone, hydramethylnon, Pyridaben, tolfenpyrad, HCN, phosphine, acequinocyl, fenazaquin, pyrimidifen, tebufenpyrad, fenpyroximate, fluacrypyrin Inhibition... 

Mitochondrial electron transport system Sulfuramid, chlorfenapyr Azocyclotin, cyhexatin, Fenbutatin-oxide, propargite, Tetradifon, diafenthiuron Uncouplers of oxidative phosphorylation Inhibitors of ATP synthase... 

Nonoxidative branch controlled primarily by substrate availability. Mitochondrial Electron Transport System... 

These findings are consistent with impaired fatty-acid oxidation reduced mitochondrial entry of long-chain acylcarnitine esters due to inhibition of the transport protein (carnitine palmityl transferase 1) and failure of the respiratory chain at complex II. Another previously reported abnormality of the respiratory chain in propofol-infusion syndrome is a reduction in cytochrome C oxidase activity, with reduced complex IV activity and a reduced cytochrome oxidase ratio of 0.004. Propofol can also impair the mitochondrial electron transport system in isolated heart preparations. 

Copper plays an important role in the constituents of many enzymes of the mammalian organism as well as in plants and anthropods. Several classes of oxidizing enzymes for copper have been described, including the cytochrome oxidases which are the terminal oxidases in the mitochondrial electron transport system, a key reaction in energy metabolism (34), and the amine oxidases (35) of which there are a number that contain copper (36,37,38), Lysyl oxidase (39) is probably the most important since it plays a major role in elastin and collagen synthesis... 

The basis for this combination is two distinct and unrelated mechanisms of action against the parasite. Atovaquone is a selective inhibitor of the Plasnuidiiim s mitochondrial electron transport system, and cycloguanil is a dihydrofolatc reductase inhibitor. Atovaquone s chemistry is based on it... 

Most of the aerobic cell s free energy is captured by the mitochondrial electron transport system (Chapter 10). During this process, electrons are transferred from a redox pair with a more negative reduction potential (NADH/NAD+) to those with more positive reduction potentials. The last component in the system is the H20/ /2 02 pair ... 

Protein-mediated electron transfer is a device used in a diverse array of biological transformadons. Well-known electron transfer processes include the mitochondrial electron transport system, photosynthesis (Chapter 13), and nitrogen flxadon (Chapter 15). Less well known biochemical reactions in which electron transfer plays a crucial role include nitric oxide synthesis and the cytochrome P450 electron transport systems. Each of these mechanisms is briefly oudined. 

Based on the structural similarity between the piercidines and co-enzyme Q, several research groups presumed and supported experimentally that the effect of the piercidines is based on competitive inhibition of the mitochondrial electron-transport systems (Hall et al., 1966 Jeng et al., 1968 Morgan et al., 1968 Morgan and Singer, 1967 Mitsui et al., 1969). Both piercidine A and piercidine B inhibit respiration at very low concentrations (Tamura et al., 1963). 

FAD is bound covalently to the enzyme protein through a specific histidine residue. Succinate dehydrogenase is tightly bound to the mitochondrial inner membrane. The importance of this binding is that the reduced flavin, which must be reoxidized for the enzyme to act again, becomes reoxidized through interaction with the mitochondrial electron transport system, also bound to the membrane. 

FADH2 is an important carrier of electrons. FAD is the oxidized form of the molecule (lacks electrons). FADH2 is the reduced form (carries electrons). FAD and FADH2 function in many oxidation reactions, such as those catalyzed by succinate dehydrogenase and fatty acyl-CoA dehydrogenase. Electrons carried by FADH2 do not pass through complex I of the mitochondrial electron transport system and thus do not result in synthesis of as many ATPs in oxidative... 

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