Fumarate reductase respiration

Fumarate is able to serve as an electron acceptor in anaerobic respiration, as it may be reduced reversibly to succinate in a two-electron process. The succinate-fumarate couple may therefore be utilized as an oxidant or reductant in the respiratory chain, and so differs from the other examples given in this section. These two reactions are catalyzed by succinate dehydrogenase and fumarate reductase, which have many similarities in subunit structure. These are shown in Table 29. Although they are different enzymes, the fumarate reductase can substitute for succinate dehydrogenase under certain conditions. The synthesis of succinate dehydrogenase is induced... 

Such a metabolism ( fumarate respiration ) is well known from anaerobic mitochondria (Tielens et al. 2002 Tielens and van Hellemond, Chap. 6 in this volume), but is unique in combination with a hydrogenase that might compete with the fumarate reductase for the same substrates. This hydrogenase of N. ovalis represents a novel type of [Fe]-only or [FeFe]-hydrogenase that allows H2 formation to be coupled directly to the reoxidation of NADH. The [Fe]-hydrogenase is linked covalently with a protein, which possesses NAD and FMN binding sites, and a ferredoxin-like FeS module that allows transfer... 

Complex II, succinate-ubiquinone oxido-reductase. Complex II, which carries electrons from succinate to ubiquinone, contains covalently linked 8 -(Af-histidyl)-FAD (Chapter 15) as well as Fe-S centers and one or more ubiquinone-binding sites. There are four subunits whose structures and properties have been highly conserved among mitochondria and bacteria and also in fumarate reductases. The latter function in the opposite direction during anaerobic respiration with fumarate as the terminal oxidant, both in bacteria and in parasitic helminths and other eukaryotes that can survive prolonged anaerobic conditions (Chapter 17, Section F,2). °° Complex II from E. coli consists of 64-, 27-, 14-, and 13-kDa subunits, which are encoded by genes sdhCDAB of a single... 

Proteoliposomes containing polysulfide reductase and either hydrogenase or formate dehydrogenase isolated from W. succinogenes do not catalyze polysulfide sulfur respiration unless 8-methyl-menaquinone is present (Table 3). Menaquinone with a side chain consisting of six or four isoprene units, or vitamin Ki served in reconstituting fumarate respiration, but did not replace 8-methyl-menaquinone in polysulfide sulfur respiration. The low activities of polysulfide sulfur respiration observed without added 8-methyl-menaquinone were probably due to the small amounts of this quinone associated with the enzyme preparations used. Maximum activity of polysulfide sulfur respiration required 10 p.mol 8-methyl-menaquinone per gram phospholipid [O. Klimmek and W. Dietrich, unpublished results]. 

The membrane-bound electron transport chains (ETC) catalyzes the transfer of reducing equivalents (protons and electrons) from NADH, glycerol-3-phosphate and lactate to oxygen, nitrate or fumarate (Sone, 1972 de Viies et al, 1972, 1977). P. pentosaceum contains a constitutive nitrate reductase and can reduce nitrate as a terminal electron acceptor during lactate utilization. Nitrate respiration is linked with the ATP synthesis (van Gent-Ruijters et al, 1975). 

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