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  • 1
    Electronic Resource
    Electronic Resource
    Identification of an UDP-glucose: Flavonol 3-O-glucosyl-transferase from cell suspension cultures of soybean (Glycine max L.) (1977)
    Springer
    Planta 136 (1977), S. 53-59 
    Details
    ISSN: 1432-2048
    Keywords: Cell culture ; Flavonoid ; Glycine ; O-glucosyltransferase ; UDP-glucose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A glucosyltransferase, which catalyses the glucosylation of flavonols, using uridine diphosphate-D-glucose as glucose donor, has been isolated and purified about 5–10 fold from cell suspension cultures of soybean (Glycine max L., var. Mandarin). The pH optimum for this reaction was ca. 8.5 in glycine-NaOH buffer, and no additional cofactors were required. The enzyme glucosylated the following flavonols predominantly at the 3-position: quercetin (Km 126 μM), kaempferol (Km 172 μM), isorhamnetin (Km 200 μM) and fisetin (Km 270 μM). With quercetin as substrate, the apparent Km value for uridine diphosphate-D-glucose was 0.3 M. Glucosylation of flavonols and flavones by this preparation occurred weakly also at the 7-position. No activity was found with dihydroquercetin, naringenin, 4,2′,4′-trihydroxychalcone, daidzein or texasin. The enzyme was specific for flavonoid compounds, since no activity was observed towards cinnamic acids or simple phenols. However, the preparation was contaminated by a vanillic acid glucosyltransferase, from which it could be partially separated by ionexchange chromatography. The specific activity of the flavonol 3-O-glucosyltransferase increased with age of the culture, reaching a maximum late in the growth cycle of the culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00387925
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  • 2
    Electronic Resource
    Electronic Resource
    Intracellular heteroplasmy for disease-associated point mutations in mtDNA: implications for disease expression and evidence for mitotic segregation of heteroplasmic units of mtDNA (1995)
    Springer
    Human genetics 〈Berlin〉 96 (1995), S. 261-268 
    Details
    ISSN: 1432-1203
    Keywords: Mitochondrial DNA ; MELAS ; Leber's hereditary optic neuropathy ; Mitochondrial disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Studies in vitro have shown that a respiratorydeficient phenotype is expressed by cells when the proportion of mtDNA with a disease-associated mutation exceeds a threshold level, but analysis of tissues from patients with mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes (MELAS) have failed to show a consistent relationship between the degree of heteroplasmy and biochemical expression of the defect. One possible explanation for this phenomenon is that there is variation of heteroplasmy between individual cells that is not adequately reflected by the mean heteroplasmy for a tissue. We have confirmed this by study of fibroblast clones from subjects heteroplasmic for the MELAS 3243 (A→ G) mtDNA mutation. Similar observations were made with fibroblast clones derived from two subjects heteroplasmic for the 11778 (G→A) mtDNA mutation of Leber's hereditary optic neuropathy. For the MELAS 3243 mutation, the distribution of mutant mtDNA between different cells was not randomly distributed about the mean, suggesting that selection against cells with high proportions of mutant mtDNA had occurred. To explore the way in which heteroplasmic mtDNA segregates in mitosis we followed the distribution of heteroplasmy between clones over approximately 15 generations. There was either no change or a decrease in the variance of intercellular heteroplasmy for the MELAS 3243 mutation, which is most consistent with segregation of heteroplasmic units of multiple mtDNA molecules in mitosis. After mitochondria from one of the MELAS 3243 fibroblast cultures were transferred to a mitochondrial DNA-free (ρ0) cell line derived from osteosarcoma cells by cytoplast fusion, the mean level and intercellular distribution of heteroplasmy was unchanged. We interpret this as evidence that somatic segregation (rather than nuclear background or cell differentiation state) is the primary determinant of the level of heteroplasmy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00210404
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    Paper (German National Licenses)
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