Ubiquinone, distribution

This complex consists of at least 25 separate polypeptides, seven of which are encoded by mtDNA. Its catalytic action is to transfer electrons from NADH to ubiquinone, thus replenishing NAD concentrations. Complex I deficiency has been described in myopathic syndromes, characterized by exercise intolerance and lactic acidemia. In at least some patients it has been demonstrated that the defect is tissue specific and a defect in nuclear DNA is assumed. Muscle biopsy findings in these patients are typical of those in many respiratory chain abnormalities. Instead of the even distribution of mitochondria seen in normal muscle fibers, mitochondria are seen in dense clusters, especially at the fiber periphery, giving rise to the ragged-red fiber (Figure 10). This appearance is a hallmark of many mitochondrial myopathies. 

Yamada, Y. Aida, K. Uemura,T. Distribution of ubiquinone 10 and 9 in acetic acid bacteria and its relation to the classification of genera Gluconobacter and Aceto-bacter, especially of so-called intermediate strains. Agric. Biol. Chem. 1968, 32, 786-788. 

The first of these new, electron transferring components was coenzyme Q (CoQ). Festenstein in R.A. Morton s laboratory in Liverpool had isolated crude preparations from intestinal mucosa in 1955. Purer material was obtained the next year from rat liver by Morton. The material was lipid soluble, widely distributed, and had the properties of a quinone and so was initially called ubiquinone. Its function was unclear. At the same time Crane, Hatefi and Lester in Wisconsin were trying to identify the substances in the electron transport chain acting between NADH and cytochrome b. Using lipid extractants they isolated a new quininoid coenzyme which showed redox changes in respiration. They called it coenzyme Q (CoQ). CoQ was later shown to be identical to ubiquinone. 

The Tte of the 3Fe-4S centre in succinate ubiquinone reductase between 4 and 8 K is decreased by interaction with paramagnetic cytochrome b.98 To mitigate the impact of spectral diffusion the relaxation times were measured by a picket-fence sequence with 100 pulses. Analysis of the powder pattern distribution of relaxation times indicated that the anisotropic dipolar interaction dominated over isotropic scalar interaction and a lower limit of 10 A was estimated for the distance between the iron-sulfur cluster and the heme. 

Kuraishi H, Katayama-Fujimura Y, Sugiyama J, Yokoyama T Ubiquinone systems in fungi. 1. Distribution of ubiquinones in the major families of ascomycetes, basidiomycetes, and deuteromycetes, and their taxonomic implications. Trans Mycol Soc Jpn 1985 26 383-395. Oberwinkler F New genera of auricularioid heterobasidiomycetes. Kept Tottori Mycol Inst 1990 28 113-127. 

Quinones.—Four menaquinone (139) homologues from Sarcina lutea have been identified as dihydromenaquinones-6, -7, -8, and -9. A novel quinone from bulbs and leaves of Iris is thought to be related to plastoquinone-9 (140) but to have a modified ring methylation pattern.No chemical data were reported. The distribution of ubiquinone (141) homologues in a number of Gram-negative bacteria has been surveyed.The biosynthesis of menaquinones and related quinones has been reviewed. The molecular structure and electronic properties of ubiquinone have been studied by semi-empirical molecular orbital theory. 

The biosynthesis of sterols takes place via the protracted sterol/isoprenoid biosynthetic pathway (Chapter 1). Although the major portion of the carbon flux through this pathway is normally directed into sterols, several branches exist leading to the production of other isoprenoid compounds needed by the cell, such as ubiquinone, dolichol and isopentenyl adenine. Total carbon flux is regulated through the enzymes of the early, or common, portion of the pathway of which the most important is HMG-CoA reductase. Distribution of carbon between the various end products is regulated at later stages of the pathway. 

Springer Sot Chem Phys 42 62-66 Cogdell RJ and Frank HA (1987) How Carotenoids function in photosynthetic bacteria. Biochim Biophys Acta 895 63-79 Condon EU (1926) A theory of intensity distribution in band systems. Phys Rev 28 1182-1201 Condon EU (1947) The Franck-Condon Principle and Related Topics. Am J Phys 15 365-374 Crofts AR and Yerkes CT (1994) A molecular mechanism for quenching. FEES Lett 352 265-270 de Grooth BG, van Grondelle R, Romijn JC and Pulles MPJ (1979) The mechanism of reduction of the ubiquinone pool in photosynthetic bacteria at different redox potential. Biochim Biophys Acta 503 480-490... 

Isoprenylated Quinones.—A review has been published on the chemistry, distribution, and functioning of vitamins A new volume in the Methods in Enzymology series contains experimental procedures used in the ubiquinone and vitamin K fields. 

C7H,o05, Mr 174.15. needles, D. 1.6, mp. 178-180°C, [a]g -157° (H2O), pKg4.15 (14.1 °C), soluble in water. S. is a widely distributed component of plants and occurs especially in fruits of the star anise (lllicium anisatum, syn. /. religiosum, Illiciaceae Japanese shi-kimi-no-ki). S. is a key intermediate of the so-called shikimic acid pathway which includes the biosynthesis of the aromatic amino acids phenylalanine, tyrosine, and tryptophan. These, in turn, are precursors of numerous alkaloids, flavonoids, and lignans, as well as 4-amino- and 4-hydroxybenzoic acid, gallic acid, tetrahydrofolic acid, ubiquinones, vitamin K, and nicotinic acid. The synthetic racemate melts at 191-192 °C. 

Ubiquinone, as the name indicates, is distributed ubiquitously. This may well explain why deficiency symptoms have not yet been observed. It is assumed to be a redox component in the respiratory chain. Mitochondria contain relatively high proportions of ubiquinone. 

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