Barley (Hordeum vulgare L.) inositol monophosphatase: gene structure and enzyme characteristics

Fu, Jianming; Peterson, Kevin; Guttieri, Mary J.; Souza, E.; Raboy, Victor

doi:10.1007/s11103-008-9343-3

Cited by 19 publications

(14 citation statements)

References 55 publications

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“…The apparent V max for VTC4 with D-Ins 3-P was 4.0 units and that for L-Gal 1-P was 5.4 units. In general, these kinetic parameters are comparable to those found for the Lilium IMP (K m of 78 mM for D-Ins 3-P; Loewus and Loewus, 1982) and kiwifruit VTC4 (K m of 150 mM for L-Gal 1-P and 330 mM for D-Ins 3-P; Laing et al, 2004; Table II), yet they differ from the previously reported values for the Synechocystis (Patra et al, 2007) and barley (Hordeum vulgare) enzymes (Fu et al, 2008), which have lower K m values (Table II). Furthermore, the ratio of V max to K m provides one measure of discriminating substrate preference, and we found that there is a 1.7-fold difference in the ratios, indicating a small difference between L-Gal 1-P and D-Ins 3-P (Table II).…”

Section: Expression Of Recombinant Atvtc4 Proteinsupporting

confidence: 79%

VTC4 Is a Bifunctional Enzyme That Affects Myoinositol and Ascorbate Biosynthesis in Plants

et al. 2009

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Myoinositol synthesis and catabolism are crucial in many multiceullar eukaryotes for the production of phosphatidylinositol signaling molecules, glycerophosphoinositide membrane anchors, cell wall pectic noncellulosic polysaccharides, and several other molecules including ascorbate. Myoinositol monophosphatase (IMP) is a major enzyme required for the synthesis of myoinositol and the breakdown of myoinositol (1,4,5)trisphosphate, a potent second messenger involved in many biological activities. It has been shown that the VTC4 enzyme from kiwifruit (Actinidia deliciosa) has similarity to IMP and can hydrolyze L-galactose 1-phosphate (L-Gal 1-P), suggesting that this enzyme may be bifunctional and linked with two potential pathways of plant ascorbate synthesis. We describe here the kinetic comparison of the Arabidopsis (Arabidopsis thaliana) recombinant VTC4 with D-myoinositol 3-phosphate (D-Ins 3-P) and L-Gal 1-P. Purified VTC4 has only a small difference in the V max /K m for L-Gal 1-P as compared with D-Ins 3-P and can utilize other related substrates. Inhibition by either Ca 2+ or Li + , known to disrupt cell signaling, was the same with both L-Gal 1-P and D-Ins 3-P. To determine whether the VTC4 gene impacts myoinositol synthesis in Arabidopsis, we isolated T-DNA knockout lines of VTC4 that exhibit small perturbations in abscisic acid, salt, and cold responses. Analysis of metabolite levels in vtc4 mutants showed that less myoinositol and ascorbate accumulate in these mutants. Therefore, VTC4 is a bifunctional enzyme that impacts both myoinositol and ascorbate synthesis pathways.

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Section: Expression Of Recombinant Atvtc4 Proteinsupporting

confidence: 79%

VTC4 Is a Bifunctional Enzyme That Affects Myoinositol and Ascorbate Biosynthesis in Plants

et al. 2009

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“…The enzyme activity of this gene is essential for the de novo synthesis of myo-Inositol (Ins) and for the recycling of Ins into Ins (1,4,5)P 3 . This enzyme is a potential regulatory point for all pathways that utilize free Ins (Fu et al 2008). Glyma12g23920 and Glyma12g29790 are both members of the Triose-phosphate Transporter family, which is in the P storage and homeostasis pathways and mediates the transport of Pi between the cytosol and the stroma of the chloroplast (Flügge et al 1989(Flügge et al , 1999Raboy et al 2001).…”

Section: Discussionmentioning

confidence: 99%

Evaluation and QTL mapping of phosphorus concentration in soybean seed

et al. 2012

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Phosphorus (P) is an essential macronutrient required for many biological and metabolic plant functions. Phosphate is the form of P used by plants.Reducing the amount of P in the seed can further aide breeding efforts to reduce the amount of P released into the environment due to the indigestibility of the complexes formed with metal ions. Analysis of the variation of phosphorus concentration in soybean seed under non-stressed conditions revealed that phosphorus ranged from 3,948.1 to 5,695.8 lg/g total phosphorous (TP) in combined years. The averages for independent years were significantly different from one another. Quantitative trait loci (QTL) analysis of TP was performed to identify candidate gene(s) that is (are) involved in P accumulation in soybean seed. One putative QTL region was identified on chromosome 12 in the combined data that contained a phosphate transporter gene. Two additional suggestive QTL were identified on chromosomes 7 and 17 with chromosome 7 having both a phosphate transport gene and a ZIP transporter gene in the region of the QTL. There were additional genes in these regions that are involved in phosphate metabolism and transport.

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“…In many plant species, MIPS1, MIPS2, and MIPS3 encode myo-inositol 3-phosphate synthase, which catalyzes the conversion of D-glucose 6-phosphate to myo-inositol 3-phosphate in the de novo myo-inositol synthesis pathway (Abid et al 2009), and IMP catalyzes the last step of the conversion of glucose 6-phosphate to myo-inositol in tomato (Gillaspy et al 1995;Styer et al 2004), barley (Fu et al 2008), soybean (Islas-Flores and Villanueva 2007), rice (Suzuki et al 2007), and kiwifruit (Laing et al 2004). RNAi suppression of MIPS activity in potato (Solanum tuberosum) results in a variety of morphological changes (Keller et al 1998;Abid et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Expression and functions of myo-inositol monophosphatase family genes in seed development of Arabidopsis

et al. 2010

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Myo-inositol monophosphatase (IMP) catalyzes the dephosphorylation of myo-inositol 3-phosphate in the last step of myo-inositol biosynthesis. IMP is also important in phosphate metabolism and is required for the biosynthesis of cell wall polysaccharides, phytic acid, and phosphatidylinositol. In Arabidopsis, IMP is encoded by VTC4. There are, however, two additional IMP candidate genes, IMPL1 and IMPL2, which have not yet been elucidated. In our genetic studies of Arabidopsis IMP genes, only the loss-of-function mutant impl2 showed embryonic lethality at the globular stage. All IMP genes were expressed in a similar manner both in the vegetative and reproductive organs. In developing seeds, expression of IMP genes was not coupled with the expression of the genes encoding myo-inositol phosphate synthases, which supply the substrate for IMPs in the de novo synthesis pathway. Instead, expression of IMP genes was correlated with expression of the gene for myo-inositol polyphosphate 1-phosphatase (SAL1), which is involved in the myo-inositol salvage pathway, suggesting a possible salvage pathway role in seed development. Moreover, the partial rescue of the impl2 phenotype by histidine application implies that IMPL2 is also involved in histidine biosynthesis during embryo development.

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Barley (Hordeum vulgare L.) inositol monophosphatase: gene structure and enzyme characteristics

Cited by 19 publications

References 55 publications

VTC4 Is a Bifunctional Enzyme That Affects Myoinositol and Ascorbate Biosynthesis in Plants

VTC4 Is a Bifunctional Enzyme That Affects Myoinositol and Ascorbate Biosynthesis in Plants

Evaluation and QTL mapping of phosphorus concentration in soybean seed

Expression and functions of myo-inositol monophosphatase family genes in seed development of Arabidopsis

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