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  • *Tropical Climate  (1)
  • Animals  (1)
  • Cyclitol biosynthesis  (1)
  • 1
    ISSN: 1432-2048
    Keywords: Cyclitol biosynthesis ; myo-Inositol 6-O-methyltransferase ; Ononitol ; Vigna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cyclitol 1d-4-O-methyl-myo-inositol (d-ononitol) is accumulated in certain legumes in response to abiotic stresses. S-Adenosyl-l-methionine:myo-inositol 6-O-methyltransferase (m6OMT), the enzyme which catalyses the synthesis of d-ononitol, was extracted from stems of Vigna umbellata Ohwi et Ohashi and purified to apparent homogeneity by a combination of conventional chromatographic techniques and by affinity chromatography on immobilized S-adenosyl-l-homocysteine (SAH). The purified m6OMT was photoaffinity labelled with S-adenosyl-l-[14C-methyl]methionine. The native molecular weight was determined to be 106 kDa, with a subunit molecular weight of 40 kDa. Substrate-saturation kinetics of m6OMT for myo-inositol and S-adenosyl-l-methionine (SAM) were Michaelis-Menten type with K m values of 2.92 mM and 63 μM, respectively. The SAH competitively inhibited the enzyme with respect to SAM (K i of 1.63 μM). The enzyme did not require divalent cations for activity, but was strongly inhibited by Mn2+, Zn2+ and Cu2+ and sulfhydryl group inhibitors. The purified m6OMT was found to be highly specific for the 6-hydroxyl group of myo-inositol and showed no activity on other naturally occurring isomeric inositols and inositol O-methyl-ethers. Neither d-ononitol, nor d-3-O-methyl-chiro-inositol, d-1-O-methyl-muco-inositol or d-chiro-inositol (end products of the biosynthetic pathway in which m6OMT catalyses the first step), inhibited the activity of the enzyme.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2011-11-05
    Description: Deposition of reactive nitrogen (N) from human activities has large effects on temperate forests where low natural N availability limits productivity but is not known to affect tropical forests where natural N availability is often much greater. Leaf N and the ratio of N isotopes (delta(15)N) increased substantially in a moist forest in Panama between ~1968 and 2007, as did tree-ring delta(15)N in a dry forest in Thailand over the past century. A decade of fertilization of a nearby Panamanian forest with N caused similar increases in leaf N and delta(15)N. Therefore, our results indicate regional increases in N availability due to anthropogenic N deposition. Atmospheric nitrogen dioxide measurements and increased emissions of anthropogenic reactive N over tropical land areas suggest that these changes are widespread in tropical forests.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hietz, Peter -- Turner, Benjamin L -- Wanek, Wolfgang -- Richter, Andreas -- Nock, Charles A -- Wright, S Joseph -- New York, N.Y. -- Science. 2011 Nov 4;334(6056):664-6. doi: 10.1126/science.1211979.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Botany, University of Natural Resources and Life Sciences, Gregor Mendel-Strasse 33, 1180 Vienna, Austria. peter.hietz@boku.ac.at〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22053047" target="_blank"〉PubMed〈/a〉
    Keywords: *Nitrogen Cycle ; Panama ; Plant Leaves ; Thailand ; *Trees ; *Tropical Climate
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-10-02
    Description: The ability of vertebrae skeletal muscle to contract more vigorously than normal in the presence of potentiating agents depends on the initial length of a muscle cell. Other factors such as the intracellular calcium ion transient, temperature, chemical nature of the potentiating agent, and the ratio of intrinsic twitch to tetanic force influence the degree of contractile potentiation but cannot account for the length dependence. At least part of a muscle cell seems normally less than fully active during contractions not only at short lengths but also at optimal sarcomere lengths.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lopez, J R -- Wanek, L A -- Taylor, S R -- NS 14268/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 1981 Oct 2;214(4516):79-82.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6974399" target="_blank"〉PubMed〈/a〉
    Keywords: Aequorin ; Animals ; Calcium/*physiology ; In Vitro Techniques ; *Muscle Contraction/drug effects ; Muscles/*physiology/ultrastructure ; Rana temporaria ; Temperature ; Zinc/pharmacology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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