Molecular Characterization of Inositol Monophosphatase Like Enzymes in Arabidopsis thaliana

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dc.contributor.authorNourbakhsh, Aidaen
dc.contributor.committeechairGillaspy, Glenda E.en
dc.contributor.committeememberSobrado, Pabloen
dc.contributor.committeememberBeers, Eric P.en
dc.contributor.committeememberKlemba, Michaelen
dc.contributor.departmentBiochemistryen
dc.date.accessioned2014-03-14T21:15:28Zen
dc.date.adate2012-07-27en
dc.date.available2014-03-14T21:15:28Zen
dc.date.issued2012-06-11en
dc.date.rdate2012-07-27en
dc.date.sdate2012-07-02en
dc.description.abstractmyo-Inositol synthesis and catabolism are crucial in many multicellular eukaryotes for production of phosphatidylinositol and inositol phosphate signaling molecules. myo-inositol monophosphatase (IMP) is a major enzyme required for the synthesis of myo-inositol and breakdown of inositol (1,4,5)-trisphosphate (InsP3), a potent second messenger involved in many biological activities. Arabidopsis contains a single canonical IMP gene, which was previously shown in our lab to encode a bifuntional enzyme with both IMP and L-galactose 1-phosphatase activity. Analysis of metabolite levels in imp mutants showed only slight modifications with less myo-inositol and ascorbate accumulation in these mutants. This result suggests the presence of other functional IMP enzymes in plants. Two other genes in Arabidopsis encode chloroplast proteins, which we have classified as IMP-like (IMPL), because of their greater homology to the prokaryotic IMPs such as the SuhB, and CysQ proteins. Prokaryotic IMP enzymes are known to dephosphorylate D-Inositol 1-P (D-Ins 1-P) and other substrates in vitro, however their in vivo substrates are not characterized. A recent study revealed the ability of IMPL2 to complement a bacterial histidinol 1-phosphate phosphatase mutant defective in histidine synthesis, which suggested an important role for IMPL2 in amino acid synthesis. The research presented here focuses on the characterization of IMPL functional roles in plant growth and development. To accomplish this I performed kinetic comparisons of the Arabidopsis recombinant IMPL1 and IMPL2 enzymes with various inositol phosphate substrates and with L-histidinol 1-phosphate, respectively. The data supports that IMPL2 gene encodes an active histidinol 1-phosphate phosphatase enzyme in contrast to the IMPL1 enzyme which has the ability to hydrolyze D-Ins 1-P substrate and may be involved in the recycling of inositol from the second messenger, InsP3. Analysis of metabolite levels in impl2 mutant plants reveals that impl2 mutant growth is impacted by alterations in the histidine biosynthesis pathway. Together these data solidify the catalytic role of IMPL2 in histidine synthesis in plants and highlight its importance in plant growth and development.en
dc.description.degreePh. D.en
dc.identifier.otheretd-07022012-113304en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-07022012-113304/en
dc.identifier.urihttp://hdl.handle.net/10919/38695en
dc.publisherVirginia Techen
dc.relation.haspartNourbakhsh_A_D_2012.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectinositolen
dc.subjectinositol monophosphataseen
dc.subjectL-histidineen
dc.subjectL-histidinolen
dc.subjectL-histidinol 1-phosphate phosphataseen
dc.subjectArabidopsis thalianaen
dc.titleMolecular Characterization of Inositol Monophosphatase Like Enzymes in Arabidopsis thalianaen
dc.typeDissertationen
thesis.degree.disciplineBiochemistryen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en
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