Production of ubiquinone-10 using bacteria

Among the bacterial strains known to contain ubiquinone-10, three strains, Agrobacterium tumefaciens KY-3085 (ATCC4452), Paracoccus denitrificans KY-3940 (ATCC19367) and Rhodobacter sphaeroides KY-4113 (FERM-P4675), were selected as excellent producers of this ubiquinone. The ubiquinone-10 production by the Agrobacterium and Rhodobacter strains was affected by aeration. An ethionine-resistant mutant (M-37) derived from A. tumefaciens KY-3085 promoted increased production of ubiquinone-10 (20% higher than the parent). Another Agrobacterium mutant (AU-55), which was induced by the successive addition of four genetic markers, showed a tolerance to the suppression of ubiquinone-10 production caused by aeration, and the fermentation time for production was remarkably shortened. The amount of ubiquinone-10 produced by this Agrobacterium mutant reached 180 mg/l in a 58 h culture. A green mutant (carotenoid-deficient mutant, Co-22-11) derived from R. sphaeroides KY-4113 produced 350 mg/l of ubiquinone-10 under culturing conditions with a limited supply of air, the ubiquinone-10 content being 8.7 mg/g-dry cell. In this case, the amount and content corresponded to 2.8 and 3.6 times larger than those given by the wild-type strain, respectively. A multiple-layer structure of cell membrane was observed in the highly ubiquinone-10 accumulating cell of the green mutant by electron microscopy. The amount of ubiquinone-10 produced by P. denitrificans was much lower than those of the other two strains.     

Distribution and redox state of ubiquinones in rat and human tissues.

The distribution and redox state of ubiquinone in rat and human tissues have been investigated. A rapid extraction procedure and direct injection onto HPLC were employed. It was found in model experiments that in postmortem tissue neither oxidation nor reduction of ubiquinone occurs. In rat the highest concentrations of ubiquinone-9 were found in the heart, kidney, and liver (130-200 micrograms/g). In brain, spleen, and intestine one-third and in other tissues 10-20% of the total ubiquinone contained 10 isoprene units. In human tissues ubiquinone-10 was also present at highest concentrations in heart, kidney, and liver (60-110 micrograms/g), and in all tissues 2-5% of the total ubiquinone contained 9 isoprene units. High levels of reduction, 70-100%, could be observed in human tissues, with the exception of brain and lung. The extent of reduction displayed a similar pattern in rat, but was generally lower.     

NADH-Ubiquinone oxidoreductase: substrate-dependent oxygen turnover to superoxide anion as a function of flavin mononucleotide

Bovine heart mitochondrial NADH-ubiquinone oxidoreductase (complex I) catalyzed NADH- and ubiquinone-1-dependent oxygen (O2) turnover to hydrogen peroxide that was stimulated by piericidin A and superoxide dismutase (SOD), but was insensitive to antimycin A, myxothiazol, and potassium cyanide. The extent of O2 consumption as a function of ubiquinone-1 did not correlate with piericidin A-sensitive rates of ubiquinone reduction. Decylubiquinone did not stimulate O2 consumption, but did initiate an SOD-sensitive cytochrome c reduction when complex I was isolated away from ubiquinol-cytochrome c oxidoreductase. Rates and extent of O2 turnover (ROS production) and ubiquinone reduction were higher than previously reported for submitochondrial particles (SMP) and isolated complex I. This ROS production was shown to co-isolate with complex I flavin.     

Ubiquinone content of eight plant species in cell culture

Crystals of ubiquinone-10 were isolated from soyabean, peanut and Ruta cell cultures, while crystals of ubiquinone-9 were obtained from rice and wheat cell cultures. These crystals also contained lesser amounts of lower and higher homologues (ubiquinone-7 to 10). The ubiquinone content of eight higher plants in cell culture was determined. Ubiquinone-9 content of rice was 680 μg per g dry wt, and this was 3–6 times higher than that of the other plants.     

Succinate-ubiquinone reductase linked recycling of alpha-tocopherol in reconstituted systems and mitochondria: requirement for reduced ubiquinone.

Studies have demonstrated that accumulation of mitochondrial tocopheroxyl radical, the primary oxidation product of alpha-tocopherol, accompanies rapid consumption of tocopherol. Enzyme-linked electron flow lowers both the steady-state concentration of the radical and the consumption of tocopherol. Reduction of tocopheroxyl radical by a mitochondrial electron carrier(s) seems a likely mechanism of tocopherol recycling. Succinate-ubiquinone reductase (complex II) was incorporated into liposomes in the presence of tocopherol and ubiquinone-10. After inducing formation of tocopheroxyl radical, it was possible to show that reduced ubiquinone prevents radical accumulation and tocopherol consumption. There was no evidence of direct reduction of tocopheroxyl radical by succinate-reduced complex II. These reactions were also measured using ubiquinone-1 and alpha-C-6-chromanol (2,5,7,8-tetramethyl-2-(4'-methylpentyl)-6-chromanol) which are less hydrophobic analogues of ubiquinone-10 and alpha-tocopherol. Mitochondrial membranes were made deficient in ubiquinone but sufficient in alpha-tocopherol and were reconstituted with added quinone. With these membranes it was shown that mitochondrial enzyme-linked reduction of ubiquinone protects alpha-tocopherol from consumption, and there is a requirement for ubiquinone. This complements the observations made in liposomes and we propose that reduced mitochondrial ubiquinones have a role in alpha-tocopherol protection, presumably through efficient reduction of the tocopheroxyl radical.     

Separation of polyprenol and dolichol by monolithic silica capillary column chromatography

We attempted an analysis of naturally occurring polyprenol and dolichol using a monolithic silica capillary column in HPLC. First, the separation of the polyprenol mixture alone was performed using a 250 x 0.2 mm inner diameter (ID) octadecylsilyl (ODS)-monolithic silica capillary column. The resolution of the separation between octadecaprenol (prenol 18) and nonadecaprenol (prenol 19) exceeded by >or=2-fold the level recorded when using a conventional ODS-silica particle-packed column (250 x 4.6 mm ID) under the same elution conditions. Next, the mixture of the prenol type (polyprenol) and dolichol type (dihydropolyprenol) was subjected to this capillary HPLC system, and the separation of each homolog was successfully achieved. During the analysis of polyprenol fraction derived from Eucommia ulmoides leaves, dolichols were found as a single peak, including all-trans-polyprenol and cis-polyprenol previously identified. This sensitive high-resolution system is very useful for the analysis of compounds that are structurally close to polyprenols and dolichols and that have a low content.     

1-Methyl-4-phenyl-2,3-dihydropyridinium is transformed by ubiquinone to the selective nigrostriatal toxin 1-methyl-4-phenylpyridinium

We have studied the interaction of coenzyme Q with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and its metabolites, 1-methyl-4-phenyl-2,3-dihydropyridinium (MPDP(+)) and 1-methyl-4-phenylpyridinium (MPP(+)), the real neurotoxin to cause Parkinson's disease. Incubation of MPTP or MPDP(+) with rat brain synaptosomes induced complete reduction of endogenous ubiquinone-9 and ubiquinone-10 to corresponding ubiquinols. The reduction occurred in a time- and MPTP/MPDP(+) concentration-dependent manner. The reduction of ubiquinone induced by MPDP(+) went much faster than that by MPTP. MPTP did not reduce liposome-trapped ubiquinone-10, but MPDP(+) did. The real toxin MPP(+) did not reduce ubiquinone in either of the systems. The reduction by MPTP but not MPDP(+) was completely prevented by pargyline, a type B monoamine oxidase (MAO-B) inhibitor, in the synaptosomes. The results indicate that involvement of MAO-B is critical for the reduction of ubiquinone by MPTP but that MPDP(+) is a reductant of ubiquinone per se. It is suggested that ubiquinone could be an electron acceptor from MPDP(+) and promote the conversion from MPDP(+) to MPP(+) in vivo, thus accelerating the neurotoxicity of MPTP.     

Ubiquinone systems of Coccidioides immitis, the causative agent of coccidioidomycosis

Abstract The ubiquinone (coenzyme Q) systems of eleven strains of Coccidioides immitis were determined by high performance liquid chromatography (HPLC). The ubiquinone profile of the fungi was shown to be homogeneous: in all of the strains, ubiquinone-10 (Q-10) was demonstrated to be the major component, with Q-9 as a minor component. The results imply that the ubiquinone system may serve as an additional phenotypic criterion for identifying the fungus.     

Production of isoprenoid compounds in the facultative methylotroph Protomonas extorquens

Screening of a strain which contained a large amount of ubiquinone Q-10 and a variety of isoprenoid compounds using different culture conditions and mutations was carried out.Protomonas extorquens TK 0045, which was found to contain carotenoid pigments, Hop-22(29)-ene, and Hopan-22-ol, was selected on the basis of cell yield and the content of ubiquinone Q-10. The contents of ubiquinone and sterols increased as the age of the culture increased, and reached a maximum level during the stationary phase.The contents of ubiquinone, sterols and carotenoid pigments, and ubiquinone homologs produced by P. extorquens TK 0045 were varied using mutagenesis. Mutants that had increased or decreased contents of carotenoid pigments were obtained with a high frequency. Most mutants had varying contents of other isoprenoid compounds. The ubiquinone homologs obtained by mutagenesis varied with a high frequency, and mutants which possessed increased levels of ubiquinone Q-9, Q-11 or Q-12 were isolated. However, the major ubiquinone component in these mutants was Q-10 the same as that in the wild strain. The production of ubiquinone was increased considerablyby repeated mutagenesis, with the content of ubiquinone produced by the third generation mutant (strains HB-5) being approximately 3.3 mg·g dry cell⁻¹ (2.5 times that of the wild strain). The acquisition of mutants exhibiting altered synthesis of carotenoid pigments would be useful for increasing the content of ubiquinone Q-10 in bacterial cells.     

Untersuchungen zur Anreicherung von Ergosterol und Ubichinonen aus Lipid-Kohlenwasserstoff-Fraktionen

Adsorption on Silicagel was used for the enrichment of ergosterol and ubiquinone-9 from a lipid-hydrocarbon extract. The main components of the lipid-hydrocarbon extract were hydrocarbons of gas oil (B. p. 513 to 653 K)phosphatides, glycerides, and fatty acids. By adsorption on silicagel (1 part silicagel to 2–3 parts of lipid-hydrocarbon extract dissolved in hexane) were ergosterol and ubiquinone-9 enriched and nearly completely separarated from hydrocarbons and phosphatides, partly from glycerides and fatty acids. Ergosterol and ubiquinone-9 can be obtained by a simplified separation from the enriched fraction.     

The role of ubiquinone in the respiratory chain of Acetobacter xylinum

1. Whole cells of Acetobacter xylinum were found to contain a quinone of the ubiquinone (coenzyme Q) group. The quinone was isolated from the cells and crystallized. It was identified by its physical, chemical and spectroscopic properties as a ubiquinone with 10 isoprene units (ubiquinone-10). No naphthaquinone was detected in the cells. 2. Cell-free extracts prepared by means of a French pressure cell were separated into three fractions by differential centrifugation. The ubiquinone was located predominantly in the particulate fraction sedimenting at 33000g, which also contained most of the NADH oxidase and malate oxidase activities. The concentration of ubiquinone-10 in extracts was similar to that of the flavoproteins and about three times the concentration of the individual cytochromes. 3. Aerobic incubations of crude extracts with either NADH or malate resulted in reduction of the endogenous ubiquinone-10 to steady-state concentrations of 55 and 40% of the total quinone respectively. In the presence of cyanide more than 95% of the endogenous ubiquinone-10 was reduced by either NADH or malate. 4. The initial rate of reduction of endogenous ubiquinone-10 by malate and the rate of ubiquinol oxidation, in A. xylinum extracts, were found to be compatible with the overall rate of malate oxidation with oxygen. 5. The effects of various respiratory inhibitors on the oxidation-reduction reactions of the endogenous quinone indicate that its position on the respiratory chain is between the malate flavoprotein dehydrogenase and the cytochrome chain.     

Full recovery of the NADH:ubiquinone activity of complex I (NADH:ubiquinone oxidoreductase) from Yarrowia lipolytica by the addition of phospholipids

NADH:ubiquinone oxidoreductase (complex I) is the largest multiprotein complex of the mitochondrial respiratory chain. His-tagged complex I purified from the strictly aerobic yeast Yarrowia lipolytica exhibited electron transfer rates from NADH to n-decylubiquinone of less than 2% when compared to turnover numbers calculated for native mitochondrial membranes from this organism. Reactivation was observed upon addition of asolectin, purified phospholipids and different phospholipid mixtures. Maximal activities of 6-7 μmol NADH min⁻¹ mg⁻¹ were observed following incubation with a mixture of 76% phosphatidylcholine, 19% phosphatidylethanolamine and 5% cardiolipin. For full reactivation, 400-500 phospholipid molecules per complex I were needed. This demonstrated that the inactivation of complex I from Y. lipolytica by general delipidation could be fully reversed simply by returning the phospholipids that had been removed during the purification procedure. Thus, our homogeneous and highly pure complex I preparation had retained its full catalytic potential and no specific, functionally essential component had been lost. As the purified enzyme was also found to contain only substoichiometric amounts of ubiquinone-9 (0.2-0.4 mol/mol), a functional requirement of this endogeneous ubiquinone could also be excluded.     

The concentration and bisynthesis of ubiquinone-9 in the liver of white rats adapted to altitude hypoxia]

The content and biosynthesis of ubiquinone-9 in the thin slices of the liver of rats was studied during altitude adaptation. There was a three-fold acceleration of ubiquinone biosynthesis during the first period of altitude adaptation. Acceleration of biosynthesis of ubiquinone-9 in rat liver was insignificant after two weeks of adaptation. The content of ubiquinone-9 in rat liver changed but insignificantly in the course of one month of altitude adaptation.     

Identification of regulatory sites in the biosynthesis of ubiquinone in the perfused rat heart

The biosynthesis of ubiquinone was studied in an isolated perfused beating heart preparation from adult male rats to determine rate-limiting steps in the biosynthetic pathway. The isolated heart could incorporate p-hydroxy[U-14C]benzoate into ubiquinones (ubiquinone-9 and -10) and two other lipids which were identified as 3-nonaprenyl 4-hydroxybenzoate and 3-decaprenyl 4-hydroxybenzoate. No other lipids could be detected. Addition of unlabeled mevalonolactone to the perfusate stimulated the rate of incorporation of p-hydroxy[U-14C]benzoate into 3-nonaprenyl 4-hydroxybenzoate and 3-decaprenyl 4-hydroxybenzoate. The level of radioactivity in these intermediates was much greater than that in ubiquinone-9 and -10. These results show that in the intact heart there is a large excess capacity to form postmevalonate isoprenoid precursors of ubiquinone and suggest a possible regulatory step at the premevalonate level. Moreover, the accumulation of prenylated derivatives of 4-hydroxybenzoic acid indicates further rate limitation at one or more of the subsequent steps in conversion of these intermediates to ubiquinone.     

Oxido-Reduction States and Natural Homologue of Ubiquinone (Coenzyme Q) in Submitochondrial Particles From Etiolated Mung Bean (Phaseolus aureus) Seedlings

A procedure for the isolation of submitochondrial particles in quantity from etiolated Mung bean (Phaseolus aureus) seedlings is described. Using a combination of acetone extraction and 2 systems of thin layer chromatography ubiquinone has been isolated. The isolated ubiquinone migrates coincident with authentic ubiquinone-10 in reversed phase thin layer partition chromatography, gives a positive Craven's test, and has oxidized and reduced spectra characteristic of ubiquinone. The quinone is partially reduced under steady-state electron transfer conditions with both succinate and NADH as substrates and is almost completely reduced under anaerobic conditions with either substrate. The concentration of ubiquinone in the particle is of the order of 4.4 mμmoles per mg particle protein, approximately equal to that found in similar submitochondrial particles from beef heart. It is tentatively concluded that ubiquinone-10 is a functional member of the mitochondrial electron transfer chain of Phaseolus aureus.     

Reactivity with ubiquinone of quinoprotein D-glucose dehydrogenase from Gluconobacter suboxydans

D-Glucose dehydrogenase is a pyrroloquinoline quinone-dependent oxidoreductase linked to the respiratory chain of a wide variety of bacteria. There is a controversy as to whether the glucose dehydrogenase is linked to the respiratory chain via ubiquinone or cytochrome b. In this study, it was shown that the glucose dehydrogenase of Gluconobacter suboxydans has the ability to react directly with ubiquinone. The enzyme purified from the membranes of G. suboxydans was able to react with ubiquinone homologues such as ubiquinone-1, -2, or -6 in detergent solution. Furthermore, in order to demonstrate the reactivity of the enzyme with native ubiquinone, ubiquinone-10, in the native membranous environment, the dehydrogenase was reconstituted together with cytochrome o, the terminal oxidase of the respiratory chain, into a phospholipid bilayer containing ubiquinone-10. The proteoliposomes thus reconstituted exhibited a reasonable glucose oxidase activity, the electron transfer reaction of which was able to generate a membrane potential and a pH gradient. Thus, D-glucose dehydrogenase of G. suboxydans has been demonstrated to donate electrons directly to ubiquinone in the respiratory chain.     

The proton-pumping NADH:ubiquinone oxidoreductase (complex I) of Aquifex aeolicus

The proton-pumping NADH:ubiquinone oxidoreductase, also called complex I, is the first energy-transducing complex of many respiratory chains. Homologues of complex I are present in the three domains of life. Here, we report the properties of complex I in membranes of the hyperthermophilic bacterium Aquifex aeolicus. The complex reacted with NADH but not with NADPH and F(420)H(2) as electron donors. Short-chain analogues of ubiquinone like decyl-ubiquinone and ubiquinone-2 were suitable electron acceptors. The affinities towards NADH and ubiquinone-2 were comparable to the ones obtained with the Escherichia coli complex I. The reaction was inhibited by piericidin A at the same concentration as in E. coli. The complex showed an unusual pH optimum at pH 9 and a maximal rate at 80 degrees C. We found no evidence for the presence of an alternative, single subunit NADH dehydrogenase in A. aeolicus membranes. The NADH:ferricyanide reductase activity of detergent extracts of A. aeolicus membranes sedimented as a protein with a molecular mass of approximately 550 kDa. From the data we concluded that A. aeolicus contains a NADH:ubiquinone oxidoreductase resembling complex I of mesophilic bacteria.     

Zur Gewinnung von Ubichinon-10 aus Acetobacter methanolicus IMET B 346

Mixtures of acetone/water (93 : 7 ··· 90 : 10, v/v) are favoured solvents for the extraction of ubiquinone-10 from Acetobacter methanolicus IMET B 346. Using these solvent mixtures ubiquinone-10 was extracted nearly completely. Other lipids were extracted partially. Extracts were obtained by optimal conditions with a ubiquinone content > 5%.     

Inhibitory effect of α-tocopherol and its derivatives on bovine heart succinate-cytochrome c reductase

α-Tocopherol and its derivatives inhibit succinate-cytochrome c reductase activity at a concentration of 0.5 μmol/mg protein in 50 mM phosphate buffer, pH 7.4, containing 0.4 % sodium cholate when α-tocopherol is predispersed in sodium cholate solution. The inhibitory site is located at the cytochrome b-c₁ region. Succinate-ubiquinone reductase activity of succinate-cytochrome c reductase was not impaired by treatment with α-tocopherol. The α-tocopherol-inhibited succinate-cytochrome c reductase activity can be reversed by the addition of ubiquinone and its analogs. When ubiquinone- and phospholipid-depleted succinate-cytochrome c reductase was treated with α-tocopherol followed by reaction with a fixed amount of 2,3-dimethoxy-6-methyl-5-(10-bromodecyl)-1,4-benzoquinone and phospholipid, the amount of α-tocopherol needed to express the maximal inhibition was only 0.3 μmol/mg protein. When ubiquinone- and phospholipid-depleted enzyme was treated with a given amount of α-tocopherol and followed by titration with 2,3-dimethoxy-6-methyl-5-(10-bromodecyl)-1,4-benzoquinone, restoration of activity was enhanced at low concentrations of ubiquinone analog, indicating that α-tocopherol can serve as an effector for ubiquinone. The maximal binding capacity of α-[¹⁴C]tocopherol, dispersed in 50 mM phosphate buffer containing 0.25% sodium cholate, pH 7.4, to succinate-cytochrome c reductase was shown to be 0.68 μmol/mg protein. A similar binding capacity, based on cytochrome b content, was observed in submitochondrial particles. Binding of α-tocopherol to succinate-cytochrome c reductase not only caused an inhibition of enzymatic activity but also caused a reduction of cytochrome c₁ in the absence of substrate, a phenomenon analogous to the removal of phospholipids from the enzyme preparation. Furthermore, binding of α-tocopherol to succinate-cytochrome c reductase decreased the rate of reduction of cytochrome b by succinate. Since electron transfer from succinate to ubiquinone was not affected by α-tocopherol treatment, the decrease in reduction rate of cytochrome b by succinate must be due to a change in environment around cytochrome b. These results as well as the fact that reactivation of α-tocopherol-inhibited enzyme requires only low concentrations of ubiquinone were used to explain the inhibitory effect as a result of a change in protein conformation and protein-phospholipid interaction rather than the direct displacement of ubiquinone by α-tocopherol. This deduction was further supported by the fact that no ubiquinone was released from succinate-cytochrome c reductase upon treatment with α-tocopherol.     

Ethanol Oxidase Respiratory Chain of Acetic Acid Bacteria. Reactivity with Ubiquinone of Pyrroloquinoline Quinone-dependent Alcohol Dehydrogenases Purified from Acetobacter aceti and Gluconohacter suhoxydans

Membrane-bound, pyrroloquinoline quinone-dependent, alcohol dehydrogenase functions as the primary dehydrogenase in the respiratory chain of acetic acid bacteria. In this study, an ability of the enzyme to directly react with ubiquinone was investigated in alcohol dehydrogenases purified from both Acetobacter aceti and Gluconobacter suboxydans by two different approaches. First, it was shown that the enzymes are able to reduce natural ubiquinones, ubiquinone-9 or -t0, in a detergent solution as well as a soluble short-chain homologue, ubiquinone-I. In order to show the reactivity of the enzyme with natural ubiquinone in a native membrane environment, furthermore, alcohol dehydrogenase was reconstituted into proteoliposomes together with natural ubiquinone and a terminal ubiquinol oxidase. The reconstitution was done by binding the detergent-free dehydrogenase at room temperature to proteoliposomes that had been prepared in advance from a ubiquinol oxidase and phospholipids containing ubiquinone by detergent dialysis using octyl-β-D-glucopyranoside; the enzyme of A. aceti was reconstituted together with ubiquinone-9 and A. aceti cytochrome a₁ while G. suboxydans alcohol dehydrogenase was done into proteoliposomes containing ubiquinone-10 and G. suboxydans cytochrome o. The proteoliposomes thus reconstituted had a reasonable level of ethanol oxidase activity, the electron transfer reaction of which was also able to generate a ‘membrane potential. Thus, it has been shown that alcohol dehydrogenase of acetic acid bacteria donates electrons directly to ubiquinone in the cytoplasmic membranes and thus the ethanol oxidase respiratory chain of acetic acid bacteria is constituted of only three membranous respiratory components, alcohol dehydrogenase, ubiquinone, and terminal ubiquinol oxidase.