VonSperberTamburiniBrunnerEtAl2015

Référence

von Sperber, C., Tamburini, F., Brunner, B., Bernasconi, S.M., Frossard, E. (2015) The oxygen isotope composition of phosphate released from phytic acid by the activity of wheat and Aspergillus Niger phytase. Biogeosciences, 12(13):4175-4184. (Scopus )

Résumé

Phosphorus (P) is an essential nutrient for living organisms. Under P-limiting conditions plants and microorganisms can exude extracellular phosphatases that release inorganic phosphate (Pi) from organic phosphorus compounds (Porg). Phytic acid (myo-inositol hexakisphosphate, IP6) is an important form of Porg in many soils. The enzymatic hydrolysis of IP6 by phytase yields available Pi and less phosphorylated inositol derivates as products. The hydrolysis of organic P compounds by phosphatases leaves an isotopic imprint on the oxygen isotope composition (δ18O) of released Pi, which might be used to trace P in the environment. This study aims at determining the effect of phytase on the oxygen isotope composition of released Pi. For this purpose, enzymatic assays with histidine acid phytases from wheat and Aspergillus niger were prepared using IP6, adenosine 50-monophosphate (AMP) and glycerophosphate (GPO4) as substrates. For a comparison to the δ18O of Pi released by other extracellular enzymes, enzymatic assays with acid phosphatases from potato and wheat germ with IP6 as a substrate were prepared. During the hydrolysis of IP6 by phytase, four of the six Pi were released, and one oxygen atom from water was incorporated into each Pi. This incorporation of oxygen from water into Pi was subject to an apparent inverse isotopic fractionation (ϵ ∼6 to 10 ‰), which was similar to that imparted by acid phosphatase from potato during the hydrolysis of IP6 (ϵ ∼7‰), where less than three Pi were released. The incorporation of oxygen from water into Pi during the hydrolysis of AMP and GPO4 by phytase yielded a normal isotopic fractionation (ϵ ∼?12 ‰), similar to values reported for acid phosphatases from potato and wheat germ. We attribute this similarity in " to the same amino acid sequence motif (RHGXRXP) at the active site of these enzymes, which leads to similar reaction mechanisms. We suggest that the striking substrate dependency of the isotopic fractionation could be attributed to a difference in the δ18O values of the C-O-P bridging and non-bridging oxygen atoms in organic phosphate compounds. © Author(s) 2015. CC Attribution 3.0 License.

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@ARTICLE { VonSperberTamburiniBrunnerEtAl2015,
    AUTHOR = { von Sperber, C. and Tamburini, F. and Brunner, B. and Bernasconi, S.M. and Frossard, E. },
    TITLE = { The oxygen isotope composition of phosphate released from phytic acid by the activity of wheat and Aspergillus Niger phytase },
    JOURNAL = { Biogeosciences },
    YEAR = { 2015 },
    VOLUME = { 12 },
    NUMBER = { 13 },
    PAGES = { 4175-4184 },
    NOTE = { cited By 14 },
    ABSTRACT = { Phosphorus (P) is an essential nutrient for living organisms. Under P-limiting conditions plants and microorganisms can exude extracellular phosphatases that release inorganic phosphate (Pi) from organic phosphorus compounds (Porg). Phytic acid (myo-inositol hexakisphosphate, IP6) is an important form of Porg in many soils. The enzymatic hydrolysis of IP6 by phytase yields available Pi and less phosphorylated inositol derivates as products. The hydrolysis of organic P compounds by phosphatases leaves an isotopic imprint on the oxygen isotope composition (δ18O) of released Pi, which might be used to trace P in the environment. This study aims at determining the effect of phytase on the oxygen isotope composition of released Pi. For this purpose, enzymatic assays with histidine acid phytases from wheat and Aspergillus niger were prepared using IP6, adenosine 50-monophosphate (AMP) and glycerophosphate (GPO4) as substrates. For a comparison to the δ18O of Pi released by other extracellular enzymes, enzymatic assays with acid phosphatases from potato and wheat germ with IP6 as a substrate were prepared. During the hydrolysis of IP6 by phytase, four of the six Pi were released, and one oxygen atom from water was incorporated into each Pi. This incorporation of oxygen from water into Pi was subject to an apparent inverse isotopic fractionation (ϵ ∼6 to 10 ‰), which was similar to that imparted by acid phosphatase from potato during the hydrolysis of IP6 (ϵ ∼7‰), where less than three Pi were released. The incorporation of oxygen from water into Pi during the hydrolysis of AMP and GPO4 by phytase yielded a normal isotopic fractionation (ϵ ∼?12 ‰), similar to values reported for acid phosphatases from potato and wheat germ. We attribute this similarity in " to the same amino acid sequence motif (RHGXRXP) at the active site of these enzymes, which leads to similar reaction mechanisms. We suggest that the striking substrate dependency of the isotopic fractionation could be attributed to a difference in the δ18O values of the C-O-P bridging and non-bridging oxygen atoms in organic phosphate compounds. © Author(s) 2015. CC Attribution 3.0 License. },
    AFFILIATION = { Institute of Agricultural Sciences, ETH Zurich, Eschikon 33, Lindau, 8315, Switzerland; Department of Biology, Y2E2 Building, Stanford University, 473 Via Ortega, Stanford, CA 94305-5020, United States; Department of Geosciences, University of Texas at El Paso, El Paso, TX 79902, United States; Geological Institute, ETH Zurich, Sonnegstrasse 5, Zurich, 8092, Switzerland },
    DOCUMENT_TYPE = { Article },
    DOI = { 10.5194/bg-12-4175-2015 },
    SOURCE = { Scopus },
    URL = { https://www.scopus.com/inward/record.uri?eid=2-s2.0-85006152654&doi=10.5194%2fbg-12-4175-2015&partnerID=40&md5=79f8e9e809e8a3f269007d5871c648e4 },
}

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