GrainGenes Reference Report: PMB-67-629
Reference
PMB-67-629
Title
Barley (Hordeum vulgare L.) inositol monophosphatase: gene structure and enzyme characteristics.
Journal
Plant Molecular Biology
Year
2008
Volume
67
Pages
629-642
Author
Fu J Peterson K Guttieri M Souza E Raboy V
Abstract
The cellular myo-inositol (Ins) pool is important to many metabolic and signaling pathways in plants. Ins monophosphatase (IMPase; EC 3.1.3.25) activity is essential for the de novo synthesis of myo-Inositol (Ins), and for recycling of Ins in Ins(1,4,5)P(3). However, proteins encoded by at least one family of IMP genes also have L: -galactose-1-P phosphatase activity important to ascorbic acid synthesis, indicating a bifunctionality that links these two branches of carbon metabolism. As part of research into the regulation of Ins synthesis and supply during seed development, the barley IMP-1 gene and gene products were studied. The 1.4 kb barley IMP-1 promoter contains one low temperature response element (RE), two heat shock REs, one gibberellin and two auxin REs, and five sugar REs. Barley IMP-1 is expressed in all tissues assayed, and expression levels were not greatly altered by abiotic stress treatments. Reduced use of Ins for Ins P(6) synthesis in developing seed of barley low phytic acid (lpa) mutants results in Ins accumulation, and IMP-1 expression is reduced in proportion to the increase in Ins level. The barley recombinant enzyme had a lower K(m), indicating higher affinity, for D/L: -Ins(3)P(1) (K(m) = 9.7 muM) as compared with reported K(m) (Ins P(1)) values for other eukaryotic IMPases (43-330 muM) or with a reported K(m) (L: -Gal-1P) of 150 muM for a kiwifruit (Actinidia deliciosa) enzyme. These and other data indicate that the barley IMP-1 gene is regulated at least in part in response to Ins metabolic needs, and that the enzyme it encodes displays catalytic properties well suited for a role in Ins synthesis, in addition to other roles as an L: -gal-1-P phosphatase important to ascorbate synthesis, or as an IMPase important to Ins(1,4,5)P(3) signal recycling.
External Databases
http://dx.doi.org/10.1007/s11103-008-9343-3
GrainGenes is a product of the Agricultural Research Service of the US Department of Agriculture.
GrainGenes Reference Report: PMB-67-629
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GrainGenes is a product of the Agricultural Research Service of the US Department of Agriculture. | |||