Kooperativer Bibliotheksverbund

Berlin Brandenburg

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  • 1
    Language: English
    In: Phytochemistry, 1980, Vol.21(12), pp.2771-2781
    Description: Synthesis of glutathione in plants seems to proceed in the same series of enzyme catalysed reactions observed in animal cells; the pathway of glutathio
    Keywords: Glutathione ; Sulphur Metabolism ; Hydrogen Peroxide ; Long-Distance Transport ; Pesticides ; Botany
    ISSN: 0031-9422
    E-ISSN: 1873-3700
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  • 2
    Language: English
    In: Phytochemistry, 1983, Vol.22(7), pp.1557-1560
    Description: Cysteine desulfhydrase activity in leaf discs of cucurbit plants is enhanced 2–4-fold by preincubation with l or d -cysteine. Preincubation with structural analogs of cysteine also stimulated the activity of the enzyme, but to a smaller extent. Maximal increase in cysteine desulfhydrase activity was observed by preincubation with 5 mM or higher concentrations of cysteine. Although not caused by activation, stimulation of the enzyme activity was half-maximal within less than 15 min. Whereas the increase in cysteine desulfhydrase activity by preincubation of leaf discs with cysteine was light independent, pretreatment of the entire plant with light or dark determined the leaf discs' potential for stimulation of the enzyme. Exposure to darkness for 4 hr reduced this potential by 60%. It is concluded that the potential for stimulation of cysteine desulfhydrase activity by preincubation with cysteine is regulated by a compound not synthesized, but metabolized, in the leaf tissue. This regulatory compound may be supplied to the leaves by long-distance transport.
    Keywords: Cucurbita Pepo ; Cucumis Sativus ; Cucurbitaceae ; Cysteine Catabolism ; Cysteine Desulfhydrase ; Hydrogen Sulfide ; Sulfur Metabolism ; Light Dependency ; Botany
    ISSN: 0031-9422
    E-ISSN: 1873-3700
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  • 3
    Language: English
    In: Phytochemistry, 1994, Vol.37(4), pp.975-977
    Description: Considerable amounts of low M r thiols were found in leaves, flowers and stems of the European mistletoe Viscum album (L.). Leaf thiol contents were the highest so far reported for green tissue. Thiol composition was similar in all mistletoe organs analysed. Glutathione was the predominant low M r thiol of V. album independent of xylem sap thiol composition of the host. From the present findings it may be concluded that either cysteine removed from the xylem sap of the host is rapidly incorporated into glutathione in the endophytic system, or glutathione is selectively removed from the xylem sap of the host. The significance of de novo reduction of sulphate taken from the xylem sap of the host for the mistletoe's thiol composition and content remains to be elucidated.
    Keywords: Viscum Albuum ; Mistletoe ; Cysteine ; Glutathione ; Thiol ; Xylem Sap ; Botany
    ISSN: 0031-9422
    E-ISSN: 1873-3700
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  • 4
    Language: English
    In: Phytochemistry, 1976, Vol.15(10), pp.1433-1434
    Description: Conditioned media of suspension cultures of Nicotiana tabacum var. Samsun contain 0.15-0.20 mmol/l glutathione. These concentrations correspond closely to the intracellular content of glutathione and represent about three to four times the amount of glutathione needed to maintain the intracellular level of glutathione. In contrast to the GSH:GSSG ratio inside the cells, the amount of GSSG in the media rises to 20% of the GSH content.
    Keywords: Nicotiana Tabacum ; Solanaceae: Tobacco ; Tissue Culture ; Conditioned Media ; Γ-Glutamyl Peptides ; Glutathione ; Botany
    ISSN: 0031-9422
    E-ISSN: 1873-3700
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  • 5
    Language: English
    In: Phytochemistry, 1987, Vol.26(6), pp.1583-1589
    Description: Emission of hydrogen sulphide in response to D -cysteine by leaf discs of cucurbit plants or cultured tobacco cells was considerably smaller than in response to L -cysteine. Whereas hydrogen sulphide emission from L -cysteine was inhibited by 100 μM aminooxyacetic acid (AOA), emission from D -cysteine was unaffected. These results from in vivo studies were found to be inconsistant with the L - and D -cysteine desulphydrase activities measured in crude homogenates. In vitro , D -cysteine desulphydrase activity was more than one order of magnitude higher than L -cysteine desulphydrase activity; L -cysteine desulphydrase was inhibited by 100 μM AOA to a smaller, D -cysteine desulphydrase to a higher extent than in vivo . Cystine lyase activity, which may interfere in the cysteine desulphydrase assay, was not found. In cucurbit leaves, the differences between in vivo and in vitro experiments can partially be explained by differences in the influx of L - and D -cysteine into the leaf discs. Influx of L -cysteine proceeded at a rate about four times higher than the influx of D -cysteine; it was inhibited by 100 μM AOA, whereas influx of D -cysteine was unaffected. Subcellular distribution of L - and D -cysteine desulphydrase was analysed in cultured tobacco cells. Both enzyme activities were found to be soluble. The D -cysteine activity was predominantly localized in the cytoplasm whereas L -cysteine activities were also found in chloroplasts and mitochondria. The L -cysteine desulphydrase in the cytoplasmic fraction may entirely be due to broken chloroplasts and mitochondria. Inhibitor studies with ammonium, pyruvate, AOA and O-acetylserine revealed considerable differences between L - and D -cysteine desulphydrase activity and between L -cysteine desulphydrase activity in chloroplasts and mitochondria. Therefore, the present data suggest that degradation of L - and D -cysteine are catalysed by different enzymes in different compartments of the cell.
    Keywords: Cucurbita Pepo ; Cucurbitaceae ; Nicotiana Tabacum ; Solanaceae ; Cysteine Catabolism ; Cysteine Desulphydrase ; D-Cysteine ; Hydrogen Sulphide ; L-Cysteine ; Subcellular Localization ; Sulphur Metabolism ; Botany
    ISSN: 0031-9422
    E-ISSN: 1873-3700
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  • 6
    Language: English
    In: Phytochemistry, 1982, Vol.21(1), pp.5-8
    Description: The low level of glutathione synthesis observed in tobacco suspension cultures grown under heterotrophic conditions was stimulated by the addition of t
    Keywords: Nicotiana Tabacum ; Solanaceae ; Tobacco ; Glutathione ; Glutathione Synthesis ; Herbicide Antidotes ; Tissue Culture ; Botany
    ISSN: 0031-9422
    E-ISSN: 1873-3700
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  • 7
    Language: English
    In: Phytochemistry, 1985, Vol.24(6), pp.1181-1185
    Description: Leaf discs, but not detached leaves, exposed to L -methionine or S -methyl- L -cysteine emitted a volatile sulphur compound identified as methanethiol by different trapping systems and by GC. Methanethiol emission was analyzed using pumpkin ( Cucurbita pepo ) leaf discs. Emission was observed in darkness or light, however methanethiol emission was greately stimulated by light. Light-dependent emission started after a lag-time of 5–6 hr with an emission peak after 36–40 hr. Maximum rates obtained were in the range of 200 pmol methanethiol/min/cm 2 leaf area. After a period of 42 hr about 60–80% of total methionine sulphur added was released as methanethiol. Addition of chloramphenicol did not alter the induction period nor the maximum emission rate of methanethiol in response to L -methionine. Emission was also observed in response to S -methyl- L -cysteine; however, the shorter lag-period for methanethiol formation suggests metabolism via a different enzyme system. In a cell-free system of pumpkin leaves methanethiol formation occured in response to L -methionine. Feeding experiments with L -[ 35 S]methionine to leaf discs showed that more than 80% of methanethiol emitted was derived from the labelled methionine fed. These findings suggest that plants have the capacity to degrade L -methionine to methanethiol. Whole leaves fed L -methionine by the petiole system do not emit methanethiol, but this compound is formed and transported into the feeding solution. Thus, methanethiol is also produced by the intact leaf, but, in contrast to sulphide, is not released into the atmosphere. It is suggested that translocation of methanethiol may function as a signal for the regulation of sulphate uptake.
    Keywords: Cucurbita Pepo ; Cucurbitaceae ; Sulphur Metabolism ; Methanethiol ; Methionine ; S-Methylcysteine ; Volatile Sulphur ; Botany
    ISSN: 0031-9422
    E-ISSN: 1873-3700
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  • 8
    Language: English
    In: Phytochemistry, 1982, Vol.21(9), pp.2173-2178
    Description: Young leaf discs of cucumber ( Cucumis sativus ) emit H 2 S at 50–100 pmol/min/cm 2 in response to 25 mM K 2 SO 4 and light. The light-de
    Keywords: Cucumis Sativus ; Cucurbitaceae ; Cucumber ; Sulfur Compounds ; Hydrogen Sulfide ; Biosynthesis ; Photosynthesis ; Sulfate Reduction ; Botany
    ISSN: 0031-9422
    E-ISSN: 1873-3700
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