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  • 2000-2004  (3)
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Material
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Biosynthesis of L-ascorbic acid (vitamin C) by Saccharomyces cerevisiae (2000)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 186 (2000), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Saccharomyces cerevisiae cells incubated with D-glucose (D-Glc), D-galactose or D-mannose (D-Man) synthesised D-erythroascorbic acid (D-EAA) but not L-ascorbic acid (L-AA). Accumulation of D-EAA was observed in cells incubated with D-arabinose (D-Ara) whilst accumulation of L-AA occurred in cells incubated with L-galactose (L-Gal), L-galactono-1,4-lactone and L-gulono-1,4-lactone. When S. cerevisiae cells were incubated with D-[U-14C]Glc, D-[U-14C]Man or L-[1-14C]Gal, incorporation of radioactivity into L-AA was observed only with L-[1-14C]Gal. Pre-incubation of yeast cells with D-Ara substantially reduced the incorporation of L-[1-14C]Gal into L-AA. Our results indicate that, under appropriate conditions, yeast cells can synthesise L-AA via the pathway naturally used for D-EAA biosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2000.tb09112.x
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  • 2
    Electronic Resource
    Electronic Resource
    Starch metabolism in developing strawberry (Fragaria × ananassa) fruits (2004)
    Oxford, UK; Malden, USA : Munksgaard International Publishers
    Physiologia plantarum 121 (2004), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Fruit starch reserves can be an important contributor to the sugar content of some ripe fruit, and despite the relatively high financial premiums (compared to other fruit) commanded by ripe strawberries, neither their starch or sugar biochemistry has been examined in detail. This study assessed the rate of starch biosynthesis and breakdown in developing strawberry and sought to determine the temporal changes in the activities of selected enzymes known to be involved in sucrose-starch interconversions. Scanning electron microscopy revealed that starch levels appeared greatest in immature strawberry (Fragaria×ananassa, cv. Elsanta) at 7 days postanthesis, as evidenced by a decrease in the number of cells containing starch granules as ripening progressed. Levels of key enzymes of starch and sugar metabolism estimated using Western blotting and enzyme activity analysis showed that activities did not correlate with antigen levels. In particular, enzyme activity recovery experiments indicated that losses were due to non-proteinaceous inhibitors, and in particular protein binding: highlighting the potential for misinterpretation of enzyme activity data gathered from ripening (strawberry) fruit tissue extracts. Consequently, in vitro experiments using [U-14C] glucose revealed that incorporation to starch is low (11%) at the earliest developmental stages when starch content is greatest. Starch synthesis rate then declines to non-detectable levels as fruit expand and ripen. These results show that starch accumulates extremely early in the fruit formation process and that starch degradation predominates during fruit growth and development. We estimate that breakdown of transient starch can contribute up to 3% of the sugar accumulated in ripe fruit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0031-9317.2004.0338.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Identification, cloning and expression analysis of strawberry (Fragaria × ananassa) mitochondrial citrate synthase and mitochondrial malate dehydrogenase (2004)
    Oxford, UK; Malden, USA : Munksgaard International Publishers
    Physiologia plantarum 121 (2004), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Salt-extractable proteins from the cell walls of immature and ripe strawberry (Fragaria × ananassa Duch. cv. Elsanta) fruit were separated using two-dimensional polyacrylamide gel electrophoresis. Seven polypeptides (enzymes) were characterized from their N-terminal sequences: (1) glyceraldhyde-3-phosphate dehydrogenase (EC 1.2.1.12); (2) triose phosphate isomerase (TPI; EC 5.3.1.1); (3) mitochondrial malate dehydrogenase (mMDH; EC 1.1.1.37); (4) NADH glutamate dehydrogenase (EC 1.4.1.3); (5) chalcone synthase (ChS; EC 2.3.1.74); (6) mitochondrial citrate synthase (mCS; EC 4.1.3.7); and (7) UDP glucose:flavonoid 3-O-glucosyltransferase (UDPG:FGT; EC 2.4.1.91). The sequenced polypeptides identified only cytosolic proteins, two of which (ChS and UDPG:FGT) had already been identified as being up-regulated in ripening (strawberry) fruit and important contributors to ripe fruit character. Our focus was therefore diverted to the enzymes mMDH and mCS for further molecular characterization as potentially important determinants of fruit flavour via regulation of the sugar : acid balance. Citrate synthase (CS) and malate dehydrogenase (MDH) enzyme activities increased substantially during ripening, as did citrate and malate contents. The increase in CS activity is supported by western blot analysis. One strawberry mCS (Fa-mCS-I) and two mMDH (Fa-mMDH-I and -II) cDNAs were cloned that were 77, 82 and 53% identical (respectively) to sequences from other plant sources. Northern analysis showed that CS and MDH expression did not correlate with enzyme activities and these findings are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0031-9317.2004.00302.x
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    Paper (German National Licenses)
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