ubiquinone-6 and ubiquinone-8

Clinical studies have identified patients with nephrotic syndrome caused by mutations in genes involved in the biosynthesis of coenzyme Q

Topics: Alkyl and Aryl Transferases; Alleles; Animals; Autophagy; Cell Line; Cells, Cultured; Disease Models, Animal; Gene Silencing; Humans; Mitochondria; Mitophagy; Nephrotic Syndrome; Organisms, Genetically Modified; Oxidative Stress; Reactive Oxygen Species; Signal Transduction; Ubiquinone; Vitamins

COQ10 deletion in Saccharomyces cerevisiae elicits a defect in mitochondrial respiration correctable by addition of coenzyme Q(2). Rescue of respiration by Q(2) is a characteristic of mutants blocked in coenzyme Q(6) synthesis. Unlike Q(6) deficient mutants, mitochondria of the coq10 null mutant have wild-type concentrations of Q(6). The physiological significance of earlier observations that purified Coq10p contains bound Q(6) was examined in the present study by testing the in vivo effect of over-expression of Coq10p on respiration. Mitochondria with elevated levels of Coq10p display reduced respiration in the bc1 span of the electron transport chain, which can be restored with exogenous Q(2). This suggests that in vivo binding of Q(6) by excess Coq10p reduces the pool of this redox carrier available for its normal function in providing electrons to the bc1 complex. This is confirmed by observing that extra Coq8p relieves the inhibitory effect of excess Coq10p. Coq8p is a putative kinase, and a high-copy suppressor of the coq10 null mutant. As shown here, when over-produced in coq mutants, Coq8p counteracts turnover of Coq3p and Coq4p subunits of the Q-biosynthetic complex. This can account for the observed rescue by COQ8 of the respiratory defect in strains over-producing Coq10p.

Topics: Cell Respiration; Electron Transport; Gene Deletion; Mitochondria; Saccharomyces cerevisiae; Ubiquinone

A novel analytical method was applied for identification of isoprenoid quinones in Escherichia coli by liquid chromatography atmospheric press chemical ionization mass spectrometry in negative mode (LC-NI-APCI-MS). Extraction and clean-up of sample were carried out on Sep-Pak Plus Silica solid-phase extraction cartridges. Ubiquinone-7 (UQ-7), Ubiquinone-8 (UQ-8) and Mequinone-8 (MK-8) were determined directly using combined information on retention time, molecular ion mass, fragment ion masses and UV characteristic spectrometry without any standard reagent. It was found that UQ-8 was the major component of isoprenoid quinones in Escherichia coli under aerobic condition. Compared with UQ-8, the relative abundance of UQ-7 and MK-8 is only 15% and 14%, respectively. The average recoveries of UQ-6, UQ-10 and vitamin K(1) in Escherichia coli were investigated by standard spiking experiment. The recoveries were achieved in the range from 94 to 106%, and the relative standard deviations (RSD) of the triplicate analysis of the spiked samples (UQ-6, UQ-10 and vitamin K(1)) ranged from 3 to 8%. The detection limits of LC-NI-APCI-MS were estimated to be 5, 40 and 0.8 microg/g dry cell for UQ-6, UQ-10 and vitamin K(1), respectively.

Topics: Chromatography, Liquid; Escherichia coli; Mass Spectrometry; Quinones; Sensitivity and Specificity; Terpenes; Ubiquinone; Vitamin K 1; Vitamin K 2

The cattle filarial parasite Setaria digitata is reported to have two ubiquinones, Q6 and Q8. These quinones are synthesized within the parasite itself and are not of host origin. Maximum concentration is found in the mitochondria of the parasite. When both Q6 and Q8 are formed and present in the adult stage, the microfilarial stage is now shown to contain only one quinone, namely Q6. Both in the adult and the mf stage, Q6 is associated with the process of electron transport. Though reduction of oxygen in S. digitata results in the generation of high concentrations of oxidants, antioxidants such as catalase and tocopherol are present in relatively lower concentrations. Hence it is proposed that the higher ubiquinone Q8 which is not involved in the electron transport process, is functioning as an antioxidant compensating for the reduced levels of classical antioxidants.

Topics: Animals; Cattle; Kinetics; Oxidoreductases; Setaria Nematode; Ubiquinone; Vitamin E

The filarial parasite Setaria digitata is unique in having two ubiquinones, Q(6) and Q(8), in the adult stage, in place of one, namely Q(10), in the host. However, the microfilariae (mf) as well as the electron transfer complexes from adult mitochondria have been recently shown to contain only Q(6). The second ubiquinone Q(8) is present only in the adult and absent in the mf. Though both Q(6) and Q(8) are present in the adult stage in the ratio 65:35, there is an enrichment of Q(8) in the excretory and secretory (ES) materials released into the incubation medium. The Q(6) level in the ES materials decreased further when the adult parasite was incubated in presence of diethylcarbamazine, a drug which inhibits the release of mf, indicating that the Q(6) detected in ES may be of mf origin. The preferential release of Q(8) into the external medium and its presence in the adult stage without any apparent role in the electron transport process strongly indicate an antioxidant role for the molecule. The inhibitory effect of Q(8) on lipid peroxidation and the presence of other components such as catalase and superoxide dismutase shown to be present in ES materials in earlier studies help the filarial parasite survive for longer periods by overcoming the oxidative reactions of the host generated against it.

Topics: Animals; Antioxidants; Catalase; Cattle; Chromatography, High Pressure Liquid; Diethylcarbamazine; Electron Transport; Filaricides; Hydroquinones; Lipid Peroxidation; Lipoxygenase Inhibitors; Mitochondria; Setaria Nematode; Superoxide Dismutase; Thiobarbituric Acid Reactive Substances; Ubiquinone