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  • 1
    Electronic Resource
    Electronic Resource
    Truffle thio-flavours reversibly inhibit truffle tyrosinase (2003)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 220 (2003), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Tyrosinase is an enzyme having two copper atoms at the reactive site occurring in prokaryotic and eukaryotic organisms. In animals tyrosinase is responsible for pigmentation, in plants for protection of injured tissues or, as in fungi, to harden cell walls. Some of us have previously shown that tyrosinase is involved in truffle development and differentiation. Here we present the purification, the molecular properties and the reversible inhibition of Tuber melanosporum tyrosinase by dimethyl-sulfide and bis[methylthio]methane, the main flavour compounds of black and whitish truffles. The MWr is 39 000. l-3,4-dihydroxyphenylalanine and l-tyrosine stain corresponding bands as expected for a true tyrosinase. Phenylthiourea, diethyldithiocarbamate and mimosine inhibit l-tyrosine and l-3,4-dihydroxyphenylalanine oxidation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0378-1097(03)00065-X
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  • 2
    Electronic Resource
    Electronic Resource
    Truffle Melanogenesis: Correlation With Reproductive Differentiation and Ascocarp Ripening (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Periodontology 2000 5 (1992), S. 0 
    Details
    ISSN: 1600-0757
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The present work uses histochemical techniques to investigate the correlation between reproductive differentiation and age of truffles (Tuber aestivum and Tuber melanosporum) with melanin synthesis. The dopa oxidase and tyrosine hydroxylase activities of tyrosinase have been localized within the ascocarp and melanin localization was performed by the Schmorl's reaction. A true tyrosinase is present in truffles, able to oxidize both 1-tyrosine and 1-dopa. The tyrosinase activity is on in the young ascocarps (in the peridium, hypothecium, and fertile veins) and off in the ripe ones, thus it appears correlated with the age and differentiation of the sporogenic hyphae that arise from the hypothecium; a similar correlation has been previously described in Neurospora crassa which is an ascomycete as well as the truffles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0749.1992.tb00538.x
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  • 3
    Electronic Resource
    Electronic Resource
    Biochemical, electrophoretic and immunohistochemical aspects of malate dehydrogenase in truffles (Ascomycotina) (2000)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 185 (2000), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The malate dehydrogenase (MDH; EC 1.1.1.37; L-malate-NAD+-oxidoreductase) activities of truffles of the genus Tuber (Tuber melanosporum Vittad., Tuber brumale Vittad., Tuber aestivum Vittad., Tuber magnatum Pico, Tuber rufum Pico) have been characterized with regard to the Km and Vmax values in the direct and reverse reactions. The isoelectrofocusing has revealed bands showing pI values ranging from pH 5.85 to 7.8. The MDH of T. melanosporum has been partially purified by hydroxyapatite treatment, DEAE-cellulose and Sephadex G-75 columns. With the partially purified T. melanosporum MDH activity polyclonal anti-T. melanosporum MDH antibodies have been prepared and used to localize MDH in the mycorrhizae and ascocarps of T. melanosporum. These antibodies inhibit T. melanosporum MDH activity as well as that of T. magnatum but not that of rabbit liver; this supports the specificity of the MDH antibodies used to localize MDH in truffle tissues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2000.tb09064.x
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of tyrosinase inhibitors on Tuber borchii mycelium growth in vitro (1999)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 180 (1999), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: This paper reports the effect of the tyrosinase (monophenol o-diphenol:oxygen oxidoreductase; EC 1.14.18.1) inhibitors diethyldithiocarbamate (DETC), L-tropolone, kojic acid, phenylthiourea (PTU) and L-mimosine on the in vitro growth of Tuber borchii (a white truffle) mycelium. A significant inhibitory effect on mycelium growth was observed for DETC, PTU and L-tropolone (0% growth compared to control at 100 μg ml−1 DETC, PTU and L-tropolone and at 10 μg ml−1 DETC and L-tropolone). As a comparison the action of the same inhibitors was also tested on the growth and pigmentation of the mould Cladosporium sphaerospermum. In the presence of CuSO4 10−6 M T. borchii mycelium acquired pigmentation (as rounded aggregates compared to control revealed by SEM microscopy). Tyrosinase activity in the extract from T. borchii mycelium (18-day culture) was detected spectrophotometrically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1999.tb08779.x
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  • 5
    Electronic Resource
    Electronic Resource
    Ploidy and chromosomal number in Tuber aestivum (1998)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 167 (1998), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Chromosome number is generally considered to be the most accurate and direct measure of ploidy. In fungi, however, counting of chromosomes is difficult and inaccurate because of their small size. To date truffles have been characterized using molecular approaches (analysis of DNA and PCR-based techniques) in order to find out differences among species, but not by a cytogenetical approach. Although the small size of truffle chromosomes is of some hindrance for a cytogenetic study, in the present work Tuber aestivum chromosome counts were determined in metaphase configurations from haploid nuclei of ascospores by aceto-orcein staining. Nuclear chromosome number and topography were also evaluated by propidium iodide DNA staining using confocal microscopy. Tuber aestivum was found to possess a basic number of 5 or 6 chromosomes, medium length ≤0.95 μm. The karyology of ascospores during their developmental stages was also investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1998.tb13214.x
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  • 6
    Electronic Resource
    Electronic Resource
    Melanosome proteins duringBufo bufo development (1985)
    Springer
    Development genes and evolution 194 (1985), S. 440-443 
    Details
    ISSN: 1432-041X
    Keywords: Melanosome differentiation ; Protein patterns ; Bufo bufo embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Changes in melanosome protein composition duringBufo bufo development have been investigated. The number of bands in SDS-PAGE varies from stage 7 (sixth cleavage) to stage 19 (heart beat), with a minimum at stages 17 (tail bud) and 19 (heart beat). At least eleven bands appear to be present throughout stages examined. The most relevant difference observed is that three protein bands of 40, 66 and 115 Kdal are expressed only at pre-neurular stages, when only maternal melanosomes are present in the embryo. Moreover, 5,6-dihydroxyindole oxidase activity has been evidenced in the gels, by specific staining. The activity appears to comigrate with tyrosinase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848560
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular approach to the nucleo-melanosomal interaction in human melanoma cells (1997)
    Springer
    Journal of neuro-oncology 31 (1997), S. 185-193 
    Details
    ISSN: 1573-7373
    Keywords: melanoma ; mutation ; tyrosinase ; 5,6-dihydroxyindole ; melanosomes ; liposomes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This paper presents evidence that L-tyrosine oxidation products and 5,6-dihydroxyindole, an intermediate of melanin synthesis bind to and modify DNA structure, as tested by extracting cell DNA, using topoisomerase I and denaturation assays. When supercoiled plasmid pCU18 or pBR322 DNAs are treated with 5,6-dihydroxyindole the supercoiled species disappear and are converted to species less mobile in a gel retardation test with respect to relaxed DNA. 5,6-Dihydroxyindole causes an easier acid denaturation of the double helix. The results, that are dose dependent,would point to both intercalation and cross-linking of DNA by 5,6-dihydroxyindole and its oxidation product(s). 3H-L-tyrosine deriving radioactivity, bound to nuclear DNA, is higher at low pH, (5.6) if compared to pH 6.8. The highest radioactivity bound to cell DNA is found during the transition from the amelanotic to the melanotic phenotype in human melanoma cell lines. As a control, the binding of 3H-L-tyrosine radioactivity to human prostate fibroblast DNA was investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005730724500
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