Biosynthesis of ubiquinone and ubichromenol in vitamin A-deficient rats

Joshi, V.C.; Ramasarma, T.

doi:10.1016/0304-4165(66)90428-4

Cited by 23 publications

(6 citation statements)

References 12 publications

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“…of liver) normal, possibly as a consequence of the lowered catabolism of the ubiquinone already occupying the available functional sites in the liver. A similar situation seems to exist in two other conditions where hepatic accumulation of ubiquinone was observed: vitamin A deficiency (Joshi & Ramasarma, 1966) and exposure to cold (Aithal et al 1968).…”

supporting

confidence: 57%

“…Orally administered ubiquinone was absorbed and retained in the liver for longer periods in vitamin A-deficient rats (Joshi & Ramasarma, 1966) and rats exposed to cold (Aithal et al 1968) than in normal animals and this was interpreted to be due to lowered catabolism. Repeating such an experiment with thyrotoxic rats revealed a peculiar feature.…”

Section: Resultsmentioning

confidence: 99%

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Metabolism of ubiquinone in relation to thyroxine status

Inamdar

Ramasarma

1969

Biochemical Journal

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1. Under conditions of thyrotoxicosis induced by feeding rats with iodinated casein, ubiquinone concentration was found to increase in the liver by increased synthesis and by partly decreased catabolism leading to its accumulation. The increased ubiquinone was found primarily in the mitochondrial and supernatant fractions. 2. Supplementing the diet with thyroxine, at less than toxic doses, also increased the synthesis and the concentration of ubiquinone in the liver. 3. In the condition of hypothyroidism obtained by feeding rats with thiouracil the concentration and the synthesis of ubiquinone in the liver showed a small decrease. 4. Synthesis of ubiquinone in liver slices was partially inhibited by addition of thyroxine in vitro. Therefore the activation effect on ubiquinone synthesis of excess of thyroxine in the intact animals appears to be by an indirect mechanism.

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supporting

confidence: 57%

Section: Resultsmentioning

confidence: 99%

Metabolism of ubiquinone in relation to thyroxine status

Inamdar

Ramasarma

1969

Biochemical Journal

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“…Therefore, it would be of interest whether chromanol analogues of UQ, such as ubichromanol (UCa) and ubichromenol (UCe), are natively present in mammalian cells and whether, in principle, chromanol analogues of UQ oxidize to UQ-like products. In the past, there have been only a few reports on the presence of UCe in liver homogenates (17)(18)(19). Links questioned some of these reports by proving that chromatographic materials, such as aluminum oxide (20), can transform UQ to UCe.…”

Section: Introductionmentioning

confidence: 99%

A New Ubiquinone Metabolite and Its Activity at the Mitochondrial bc₁ Complex

Gille

Stamberg

Jäger

et al. 2007

Chem. Res. Toxicol.

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Ubichromanol, a reductive cyclization product of ubiquinone, acts as radical scavenging antioxidant and is similarly effective as alpha-tocopherol. However, nothing is known so far on the two-electron oxidation product of this antioxidant and its bioactivity. This study demonstrates that ubichromanol yields a ubiquinone-like compound with a hydroxyl-substituted side chain (UQOH) on oxidation. HPLC/MS and HPLC/ECD measurements revealed its natural presence in bovine liver mitochondria. The bioactivity of this formerly unknown compound as substrate for mitochondrial complex III was tested by measurements of the quinol:cytochrome c oxidoreductase activity in bovine submitochondrial particles and isolated mitochondrial bc1 complex. Consistently in both model systems, reduced UQOH exhibited substrate efficiencies below that of native ubiquinone but a significantly higher efficiency than alpha-tocopheryl quinone. Model calculations revealed that on binding of reduced UQOH to the bc1 complex the polar hydroxyl group was located close to hydrophobic amino acid residues. This fact could in part explain the lower efficiency of reduced UQOH in comparison to ubiquinone as a substrate for the mitochondrial bc1 complex. Therefore, the hydroxylation of the aliphatic or isoprenoid side chains of bioquinones, which is typical for quinoid oxidation products of chromanols, such as alpha-tocopherol and ubichromanol, disturbs substrate binding at the mitochondrial electron-transfer complexes, which usually interact with ubiquinone.

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“…Morton and coworkers [4] at the University of Liverpool (UK) independently discovered the same compound, and named it ubiquinone. Helping in its isolation was the advantage of its enormous increase in the livers of animal deficient in vitamin A, later found to be due to decreased catabolism [5]. The native molecule was absorbed through intestines into liver, and was degraded, but not when the sidechain double bonds were saturated by catalytic hydrogenation [6].…”

Section: Introductionmentioning

confidence: 99%

Relaxation of arterial smooth muscle: A new function of a water‐soluble degradation product of coenzyme Q (ubiquinone)

et al. 2003

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Treatment of coenzyme Q with ozone yielded a degradation product having unmodified ring that retained its spectral characteristics and a truncated side-chain that made it water-soluble. This derivative, but not the intact lipid-quinone, showed relaxation of phenylephrine-contracted rat arterial rings. This effect offers an explanation for the known hypotensive action of exogenous coenzyme Q regardless of its side-chain length.

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Biosynthesis of ubiquinone and ubichromenol in vitamin A-deficient rats

Cited by 23 publications

References 12 publications

Metabolism of ubiquinone in relation to thyroxine status

Metabolism of ubiquinone in relation to thyroxine status

A New Ubiquinone Metabolite and Its Activity at the Mitochondrial bc₁ Complex

Relaxation of arterial smooth muscle: A new function of a water‐soluble degradation product of coenzyme Q (ubiquinone)

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Biosynthesis of ubiquinone and ubichromenol in vitamin A-deficient rats

Cited by 23 publications

References 12 publications

Metabolism of ubiquinone in relation to thyroxine status

Metabolism of ubiquinone in relation to thyroxine status

A New Ubiquinone Metabolite and Its Activity at the Mitochondrial bc1 Complex

Relaxation of arterial smooth muscle: A new function of a water‐soluble degradation product of coenzyme Q (ubiquinone)

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A New Ubiquinone Metabolite and Its Activity at the Mitochondrial bc₁ Complex