Disease relevance of ubiquinone-10

• Using 1-, 2-, 3- and 4-13C site-specifically labelled ubiquinone-10, reconstituted at the QA site of Rhodobacter sphaeroides R26 reaction centres, the infra-red bands dominated by the 1- and 4-C = O vibration of QA are assigned in the QA(-)-QA difference spectra [1].
• Decreased serum ubiquinone-10 concentrations in phenylketonuria [2].
• Taken together, these data suggest that pharmacological doses of probucol retard atherogenesis in WHHL rabbits by an antioxidant mechanism, while ubiquinone-10 and vitamin E at these dosages are ineffective in this highly hyperlipidaemic model [3].
• We showed that the two proteins must be present simultaneously in Escherichia coli transformants before ubiquinone-10, which is produced by S. pombe but not by E. coli, is generated [4].
• The mechanisms leading to elevated plasma ubiquinone-10 in kwashiorkor require further studies [5].

High impact information on ubiquinone-10

• Effect of an inhibitor of 3-hydroxy-3-methyglutaryl coenzyme A reductase on serum lipoproteins and ubiquinone-10-levels in patients with familial hypercholesterolemia [6].
• Effects of an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme a reductase on serum lipoproteins and ubiquinone-10 levels in patients with familial hypercholesterolemia. 1981 [7].
• These results indicated that the S. cerevisiae Ndi1 was expressed functionally in CCL16-B2 cells and catalyzed electron transfer from NADH in the matrix to ubiquinone-10 in the inner mitochondrial membranes [8].
• First, alpha-TQH2 readily associated with LDL and instantaneously reduced the lipoprotein's ubiquinone-10 to CoQ10H2, thereby maintaining this antioxidant in its active form [9].
• In this paper we show that ubiquinol-10, the reduced form of ubiquinone-10, also efficiently scavenges free radicals generated chemically within liposomal membranes [10].

Chemical compound and disease context of ubiquinone-10

• Electron transfer from P+QA-QB to form P+QAQB- was measured in Rhodobacter sphaeroides R-26 reaction centers (RCs) where the native primary quinone, ubiquinone-10 (UQA), was replaced by 2-methyl-3-phytyl-1,4-naphthoquinone (MQA) [11].
• The absorption frequencies of the C = O and C = C (neutral state) and of the C...O (semiquinone state) stretching vibrations of QB have been assigned by FTIR spectroscopy, using native and site-specifically 1-, 2-, 3- and 4-13C-labelled ubiquinone-10 (UQ10) reconstituted at the QB binding site of Rhodobacter sphaeroides R26 reaction centres [12].
• Using picosecond absorption spectroscopy it has been shown that in Rhodobacter sphaeroides reaction centres the substitution of the primary quinone acceptor (QA), ubiquinone-10, by other quinone species (with redox potentials higher or lower than that of ubiquinone-10) has essentially no modifying effect on the reaction centre protein [13].
• The QMDP-66 or ubiquinone-10 treatment, however, did not alleviate the decrease in body weight gain or ventricular weight due to adriamycin [14].
• Plasma phenylalanine is associated with decreased serum ubiquinone-10 concentrations in phenylketonuria [15].

Biological context of ubiquinone-10

• The concentrations of ubiquinone-9 and ubiquinone-10, substances involved in electron transport and efficient antioxidants, were both decreased in BDL rats 14 and 28 days after surgery per gram of liver and per milligram of mitochondrial protein [16].
• The enzymatic activity underlying the respiratory burst in human neutrophils was examined in a subcellular fraction with high specific activity and shown to be a membrane-associated complex of a flavoprotein, ubiquinone-10, and cytochrome b559 in an approximate 1.3:1:2 molar ratio [17].
• We therefore tested the effect of ubiquinone-10 (CoQ10) supplemented at 1% (w/w) on aortic lipoprotein lipid peroxidation and atherosclerosis in apolipoprotein E-deficient (apoE-/-) mice fed a high-fat diet [18].
• When the enzymes had been supplemented with further phospholipid and ubiquinone-10 the kinetics were monophasic [19].
• The following pattern of activities was obtained: (1) Reconstitution of cyclic photophosphorylation with ubiquinone-10 was saturated at about 40 ubiquinone molecules per reaction center [20].

Anatomical context of ubiquinone-10

• We conclude that activation of the oxidase enzyme complex in the intact neutrophil resulted in linkage of electron carrier function between endogenous ubiquinone-10 and cytochrome b559 and was without demonstrable effect on proximal electron flow [17].
• Stopped-flow rapid-scan spectrophotometry was employed to study complicated oxidation processes of ubiquinol-cytochrome c reductase (QCR) that was purified from bovine heart mitochondria and maximally contained 0.36 mol of ubiquinone-10/mol of heme c1 [21].
• A similar trend was observed in ubiquinone-10-enriched lymphocytes when compared with control cells [22].
• In women only, NK cell cytotoxicity at different effector-target cell ratios was positively associated with plasma vitamin E and ubiquinone-10 concentrations (P < 0.05) [23].
• Ubiquinone-10 has recently been proposed as a component of the microbicidal oxidase system of neutrophil leukocytes [Crawford & Schneider (1982) J. Biol. Chem. 257, 6662-6668] [24].

Associations of ubiquinone-10 with other chemical compounds

• The role of ubiquinone in this process was evaluated by fusing liposomes containing ubiquinone-10 or ubiquinone-6, with inner membranes [25].
• Hence, we identify a single molecule of quinone, probably ubiquinone-10 in a special environment, as a major electron donor to ferricytochrome c2 in the ubiquinone cytochrome b-c2 oxidoreductase [26].
• Inhibition of the active oxidase complex by p-chloromercuribenzoate also inhibited electron flow from NADPH to all purported electron carriers in the chain (i.e. E-FAD, ubiquinone-10, and cytochrome b559) [17].
• Purified L-3-glycerophosphate dehydrogenase from pig brain mitochondria interacts with ubiquinone-10 and ubiquinol-cytochrome c oxidoreductase (Complex III) from bovine heart mitochondria to reconstitute antimycin-sensitive L-3-glycerophosphate- cytochrome c oxidoreductase [27].
• Ubiquinol-10, the reduced form of ubiquinone-10 (coenzyme Q10), is a potent lipophilic antioxidant present in nearly all human tissues [28].

Gene context of ubiquinone-10

• Expression of COQ2 from Saccharomyces cerevisiae in the defective S. pombe strain restored growth and enabled the cells to produce ubiquinone-10, indicating that COQ2 and ppt1 are functional homologs [29].
• An increased ubiquinone-10 content in the mitochondrial membrane of all the mutants, and enhanced succinate dehydrogenase and citrate synthase activities in the ND4 mutant, are proposed to be compensatory changes [30].
• Since 2 of these last ubiquinones are integral parts of the photochemical reaction center, we conclude that the ubiquinone-cytochrome b-c2 oxidoreductase requires only 1, or at most 2, molecules of ubiquinone-10 for its function [26].
• Activation of the human neutrophil NADPH oxidase results in coupling of electron carrier function between ubiquinone-10 and cytochrome b559 [17].
• In search of the pathophysiology of this disorder, another mevalonate kinase product, ubiquinone-10, was studied [31].

Analytical, diagnostic and therapeutic context of ubiquinone-10

• Serum ubiquinone-10 concentrations were analyzed by HPLC with electrochemical detection [32].
• Mevalonic acid in body fluids was determined by stable isotope dilution gas chromatography/mass spectroscopy with selected ion monitoring, ubiquinone-10 concentrations by reversed-phase high-pressure liquid chromatography [33].
• The distribution of ubiquinone-10 in phospholipid bilayers. A study using differential scanning calorimetry [34].
• These data suggest that at molar percentages less than 20% ubiquinone-10 a high proportion of the coenzyme is molecularly mixed within the phospholipid bilayer but as the proportion increases there is a greater tendency for the coenzyme to form aggregates that display typical melting and crystallization behaviour [34].

References