Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.6.5.3 (complex I)
 8,901 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The hydrophobic isoprene tail of ubiquinone-2 (Q2) exihibits binding specificity in redox reactions with bovine heart mitochondrial complex I (Ohshima, M., Miyoshi, H., Sakamoto, K., Takegami, K., Iwata, J., Kuwabara, K., Iwamura, H., and Yagi, T. (1998) Biochemistry 37, 6436-6445) and the Escherichia coli bo-type ubiquinol oxidase (Sakamoto, K., Miyoshi, H., Takegami, K., Mogi, T., Anraku, Y., and Iwamura, H. (1996) J. Biol. Chem. 271, 29897-29902). To identify the structural factor(s) of the diprenyl tail of Q2 governing the specific interaction with these enzymes, we synthesized a series of novel Q2 analogues in which only one of the structural factors of the diprenyl tail was systematically modified. In bovine complex I, the presence of the methyl branch and the pi-electron system in the first isoprene unit are responsible for high-affinity binding of Q2 to the ubiquinone reduction site, which results in a low Km and kcat values of Q2 reduction. The position of the methyl group in the tail is strictly recognized by the enzyme. In contrast to complex I, in bo-type ubiquinol oxidase, either of the two pi-electron systems in the tail is required for high-affinity binding of Q2H2 to the enzyme, while the presence of the methyl branch and the location of the pi-electron systems are not strictly recognized by the enzyme. We concluded that the role of the ubiquinone tail is not simply the enhancement of the hydrophobicity of the molecule and that molecular recognition of the tail by the quinone redox site differs among the respiratory enzymes.
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PMID:Role of the isoprenyl tail of ubiquinone in reaction with respiratory enzymes: studies with bovine heart mitochondrial complex I and Escherichia coli bo-type ubiquinol oxidase. 979 Jun 73

CoQ (coenzyme Q), an isoprenylated benzoquinone, is a well-known component of the electron-transfer system in eukaryotes. The main role of CoQ is to transfer electrons from NADH dehydrogenase and succinate dehydrogenase to CoQ:cytochrome c reductase in the respiratory chain. However, recent evidence indicates that an involvement in respiration is not the only role of CoQ. The second apparent role of CoQ is its anti-oxidation property, and other novel roles for CoQ, such as in disulfide-bond formation, sulfide oxidation and pyrimidine metabolism, have been reported. CoQ10, having ten isoprene units in the isoprenoid side chain, has been used as a medicine and is now commercially popular as a food supplement. Two yeast species, namely the budding yeast Saccharomyces cerevisiae, which produces CoQ6, and the fission yeast Schizosaccharomyces pombe, which produces CoQ10, are the main subjects of the present minireview because they have greatly contributed to our basic knowledge of CoQ biosynthesis among eukaryotes. The biosynthetic pathway that converts p-hydroxybenzoate into CoQ consists of eight steps in yeasts. The five enzymes involved in the biosynthetic pathway have been identified in both yeasts, yet the functions of three proteins were still not known. Analyses of the biosynthetic pathway in yeasts also contribute to the understanding of human genetic diseases related to CoQ deficiency. In the present minireview I focus on the biochemical and commercial aspects of CoQ in yeasts and in other organisms for comparison.
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PMID:Biosynthesis and bioproduction of coenzyme Q10 by yeasts and other organisms. 1953 Oct 29

NADH-ubiquinone oxidoreductase (Complex I) is located at the entrance of the mitochondrial electron transfer chain and transfers electrons from NADH to ubiquinone with 10 isoprene units (Q(10)) coupled with proton pumping. The composition of Complex I, the largest and most complex proton pump in the mitochondrial electron transfer system, especially the contents of Q(10) and phospholipids, has not been well established. An improved purification method including solubilization of mitochondrial membrane with deoxycholate followed by sucrose gradient centrifugation and anion-exchange column chromatography provided reproducibly a heme-free preparation containing 1 Q(10), 70 phosphorus atoms of phospholipids, 1 zinc ion, 1 FMN, 30 inorganic sulfur ions, and 30 iron atoms as the intrinsic constituents. The rotenone-sensitive enzymatic activity of the Complex I preparation was comparable to that of Complex I in the mitochondrial membrane. It has been proposed that Complex I has two Q(10) binding sites, one involved in the proton pump and the other functioning as a converter between one and two electron transfer pathways [Ohnishi, T., Johnson, J. J. E., Yano, T., LoBrutto, R., and Widger, R. W. (2005) FEBS Lett. 579, 500-506]. The existence of one molecule of Q(10) in the fully oxidized Complex I suggests that the affinity of Q(10) to one of the two Q(10) sites is greatly dependent on the oxidation state and/or the membrane potential and that the Q(10) in the present preparation functions as the converter of the electron transfer pathways which should be present in any oxidation state.
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PMID:Bovine heart NADH-ubiquinone oxidoreductase contains one molecule of ubiquinone with ten isoprene units as one of the cofactors. 1996 Dec 38