Netsu Sokutei
Online ISSN : 1884-1899
Print ISSN : 0386-2615
ISSN-L : 0386-2615
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Volume 33, Issue 1
Displaying 1-5 of 5 articles from this issue
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  • Cold Adaptation and Molecular Evolution of Enzyme
    Akihiko Yamagishi
    2006 Volume 33 Issue 1 Pages 2-9
    Published: January 31, 2006
    Released on J-STAGE: September 07, 2009
    DOIhttps://doi.org/10.11311/jscta1974.33.2
    JOURNAL FREE ACCESS
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    There are many cold places around the Earth. From the psychrophiles isolated from those environments, cold-adapted enzymes have been isolated. Cold-adapted enzymes have sufficient activity and sufficient substrate-affinity to support the growth, and show low thermo-stability. Artificially cold-adapted enzymes have been obtained by evolutionary engineering from thermophile enzymes. The analysis revealed one of the cold-adaptation mechanisms: the cold-adapted enzymes showed lower enthalpy of substrate-binding thus providing lower activation enthalpy for high activity at low temperature. Some of the cold-adapted enzymes retained high thermal stability of the original thermophile enzyme. The results suggest that it is possible to reconcile high stability with high activity at low temperature. However, the issue needs further investigation. It has been elucidated that life evolved from the hyperthermophilic common ancestor (Commonote). Accordingly, the in vitro evolution experiments for obtaining cold-adapted enzymes from thermophile enzyme are, in a sense, reproducing the evolution of life.
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  • Phase Transition of Lipids in Overwintering Insects
    Chihiro Katagiri
    2006 Volume 33 Issue 1 Pages 10-19
    Published: January 31, 2006
    Released on J-STAGE: September 07, 2009
    DOIhttps://doi.org/10.11311/jscta1974.33.10
    JOURNAL FREE ACCESS
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    Lipid is one of the major components in organisms; that is, triacylglycerols and phospholipids are known as an energy source and the major constituent of the membrane, respectively. Their transition between liquid and solid occurs often under the biological environments. Insects are ectotherm of tropical origin. They, however, flourish everywhere on the earth except ocean. We have investigated how they can survive during the cold winter. Insects sometimes avoid and sometimes utilise the thermal transition of the lipids above and hydrocarbons that cover the body surface against dehydration.
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  • Trehalose: a Molecule Responsible for Desiccation Tolerance in the Sleeping Chironomid, Polypedilum Vanderplanki
    Takashi Okuda
    2006 Volume 33 Issue 1 Pages 20-26
    Published: January 31, 2006
    Released on J-STAGE: September 07, 2009
    DOIhttps://doi.org/10.11311/jscta1974.33.20
    JOURNAL FREE ACCESS
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    Life and death are mutually exclusive states. But some organisms showing no sign of living due to complete desiccation are nevertheless able to resume active life after rehydration. This peculiar biological state of organisms is referred to as cryptobiosis. Larvae of an insect species, the African chironomid Polypedilum vanderplanki, live in temporary rock pools in semi-arid areas and are able to achieve cryptobiosis. P. vanderplanki larvae accumulate trehalose to levels of about 20% of their dry weight (40μg/individual) upon cryptobiosis. Quickly desiccated larvae accumulated little trehalose and failed to recover after rehydration. A classical insect endocrine technique revealed that P. vanderplanki larvae without brain could synthesize trehalose and enter cryptobiosis successfully, in spite of the fact that the brain has a significant role in regulating both induction and termination of insect diapause. Tissues isolated from P. vanderplanki larvae could be preserved in a dry state at room temperature for 18 months in viable form. This confirms that central nervous system is not involved in cryptobiosis-induction, even in such a multicellular and rather complex organism, P. vanderplanki. Vitrification of trehalose seemed to be of significance for stabilizing cryptobiosis in P. vanderplanki.
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  • Precise Evaluation of Enzyme Activity using Isothermal Titration Calorimetry
    Nurul Karim, Shun-ichi Kidokoro
    2006 Volume 33 Issue 1 Pages 27-35
    Published: January 31, 2006
    Released on J-STAGE: September 07, 2009
    DOIhttps://doi.org/10.11311/jscta1974.33.27
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    Isothermal titration Calorimetry (ITC) has become a powerful method for evaluating enzyme kinetics, as it provides a way to detect catalytic reaction heat as a function of time with high sensitivity and reproducibility. This review focuses on both established and newly emerging methodologies for evaluating the kinetics of enzyme-catalyzed reactions. Because it allows direct determination of the reaction rate, which itself indicates enzyme activity, ITC is expected to provide a general and effective way to evaluate enzyme activity. The theoretical basis of ITC for evaluating enzyme kinetics is reviewed, as demonstrates the advantages of this method.
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  • [title in Japanese]
    2006 Volume 33 Issue 1 Pages 36-38
    Published: January 31, 2006
    Released on J-STAGE: September 07, 2009
    DOIhttps://doi.org/10.11311/jscta1974.33.36
    JOURNAL FREE ACCESS
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