Coenzyme Q reductase

NADH coenzyme Q reductase defect (complex I) Succinate coenzyme Q reductase defect (complex II) Coenzyme Q cytochrome C reductase defect (complex III)... 

Iron centers undergo cyclic oxidoreduction between ferrous and ferric states, as shown here. Complex I is also called NADH-coenzyme Q reductase because the electrons are used to reduce coenzyme Q. The passage through Complex I can be blocked by the compounds rotenone and amytal and the artificial electron acceptor methylene blue can accept electrons from FMNH2 Figure 15.9. 

Complex II (succinate dehydrogenase) - Complex II is not in the path traveled by electrons from Complex I (Figure 15.3). Instead, it is a point of entry of electrons from FADH2 produced by the enzyme succinate dehydrogenase in the citric acid cycle. Both complexes I and II donate their electrons to the same acceptor, coenzyme Q. Complex II, like complex I, contains iron-sulfur proteins, which participate in electron transfer. It is also called succinate-coenzyme Q reductase because its electrons reduce coenzyme Q. 

Succinate dehydrogenase (also called succinate-coenzyme Q reductase or Complex II) is an enzyme of the citric acid cycle and glyoxylate cycle that catalyzes the reaction below ... 

FIG. 4.2 Malate metabolism in mitochondria from body wall muscle of adult Ascaris smm. (1) Fumarase (2) malic enzyme (3) pyruvate dehydrogenase complex (4) complex I (5) succinate-coenzyme Q reductase (complex II, fumarate reductase) (6) acyl CoA transferase (7) methylmalonyl CoA mutase (8) methyl-malonyl CoA decarboxylase (9) propionyl CoA condensing enzyme (10) 2-methyl acetoacetyl CoA reductase (11) 2-methyl-3-oxo-acyl CoA hydratase (12) electron-transfer flavoprotein (13) 2-methyl branched-chain enoyl CoA reductase (14) acyl CoA transferase. 

Takamiya, S., Furushima, R. and Oya, H. (1986) Electron-transfer complexes of Ascaris suum muscle mitochondria. II. Succinate coenzyme Q reductase (complex II) associated with substrate-reducable cytochrome B g. Biochim. Biophys. Acta 848 99-107. 

Complex II, also known as succinate-coenzyme Q reductase, accepts electrons from succinate formed during the TCA cycle (see the previous chapter). Electrons flow from succinate to FAD (the flavin-adenine dinucleotide) coenzyme, through an iron-sulfur protein and a cytochrome bsso protein (the number refers to the wavelength where the protein absorbs), and to coenzyme Q. No protons are translocated by Complex II. Because translocated protons are the source of the energy for ATP synthesis, this means that the oxidation of a molecule of FADH2 inherently leads to less ATP synthesized than does the... 

A protein complex capable of rapidly reducing coenzyme Q in the presence of succinate (succinic coenzyme Q reductase), NADH (NADH coenzyme Q reductase), and cytochrome c (cytochrome c coen-... 

Villalba, J. M., Navarro, F., Cordoba, F., Serrano, A., Arroyo, A., Crane, F. L., and Navas, P., 1995, Coenzyme Q reductase from liver plasma membrane Purification and role in trans-plasma-membrane electron transport, Proc. Natl. Acad. Sci. (USA), 92 4887-4891. 

Coenzyme Q reductase, 260 reaction with arylazido-j3-alanine NAD, 284, 285... 

Respiratory-chain disorders (with mitochondrial myopathy) Lactic Various, including cytochromes b, aa, cytochrome c oxidase, NADH-coenzyme Q reductase 15.6... 

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