Inositol Synthesis and Catabolism in Plants

该项目利用分子、遗传和生化工具来解决大多数生物体中存在的产生大量必需代谢物的基本途径。在许多多细胞真核生物中，肌醇的合成和分解代谢是产生磷脂酰肌醇信号分子、甘油磷脂肌醇膜锚、细胞壁果胶非纤维素多糖、维生素C和其他几种分子的关键。肌醇的合成和分解代谢在植物和开创性的生化实验中尤其重要，从20世纪60年代的S和70年代的S定义了所有涉及的主要酶。编码肌醇单磷酸酶(IMP；EC 3.1.3.25)和肌醇加氧酶(MIOX；E.C.1.13.99.1)的多基因家族存在于拟南芥的植物模型系统中。该项目将解决IMP和MIOX基因在为各种途径提供肌醇方面具有特殊作用的假设。为了验证这一假设，我们将研究IMP和MIOX的表达模式。为了解决不同的IMP和MIOX亚型是否具有不同的催化活性，将生产重组蛋白并确定其底物特异性。对这一方法的补充将是基因分析，这对确定体内功能至关重要。将利用气相色谱-质谱仪进行代谢谱分析，以确定每种异构体对肌醇、磷脂酰肌醇、D-葡萄糖醛酸、半乳糖醇、抗坏血酸和其他肌醇代谢物水平的影响。肌醇的合成和分解代谢途径为植物和动物的许多细胞功能提供了肌醇。该项目将研究模式植物如何控制肌醇的合成，以满足其不同的需求。由于植物中肌醇周转的动态可以通过土壤磷污染来影响环境，这项研究将提供关于限制这种污染的可能方法的知识。此外，在糖尿病、唐氏综合症、阿尔茨海默氏症和躁郁症等疾病中，肌醇的合成也会发生变化。因此，研究肌醇代谢的基础科学对于了解这些疾病的病理也是至关重要的。

This project utilizes molecular, genetic and biochemical tools to address a fundamental pathway present in most organisms that gives rise to a large number of required metabolites. Myo-inositol synthesis and catabolism is crucial in many multiceullar eukaryotes for production of phosphatidylinositol signaling molecules, glycerophosphoinositide membrane anchors, cell wall pectic non-cellulosic polysaccharides, Vitamin C, and several other molecules. Myo-inositol synthesis and catabolism are especially important in plants and ground-breaking biochemical experiments from the 1960's and 70's defined all of the major enzymes involved. Multigene families encoding myo-inositol monophosphatase (IMP; EC 3.1.3.25), and myo-inositol oxygenase (MIOX; E.C. 1.13.99.1) enzymes are present in the plant model system, Arabidopsis thaliana. The project will address the hypothesis that the IMP and MIOX genes have specialized roles in providing inositol for various pathways. To test this hypothesis, IMP and MIOX expression patterns will be examined. To address whether the different IMP and MIOX isoforms have different catalytic activities, recombinant proteins will be produced and their substrate specificities determined. Complementing this approach will be a genetic analysis which is crucial for determining function in vivo. Metabolic profiling by gas chromatography-mass spectrometry will be utilized to determine the effect of each isoform on levels of the myo-inositol, phosphatidylinositol, D-glucuronic acid, galactinol, ascorbic acid, and other inositol metabolites as required. The inositol synthesis and catabolism pathway provides inositol for many required cellular functions of both plants and animals. This project will investigate how a model plant controls the synthesis of inositol to meet its varying needs. Since the dynamics of inositol turnover in plants can impact the environment through phosphorous contamination of soil, this research will provide knowledge about possible ways to limit such contamination. As well, inositol synthesis is altered in diseases such as diabetes, Down's syndrome, Alzheimer's and bipolar disorder. Thus investigating the basic science of inositol metabolism is vital also for understanding the pathology of these diseases.