Doctoral Training/Biochemistry/Transsulfuration Enzymes

描述（由申请人提供）： 该项目的广泛，长期目标是了解酶的结构和功能关系，催化cystaline周围的反应，一个中央中间体的trans-sulfation途径，相互转换半胱氨酸和同型半胱氨酸。转硫酶在提供生长所需的半胱氨酸和蛋氨酸以及调节这些氨基酸的体内平衡方面起着重要作用。 人类的某些遗传疾病，如同型半胱氨酸血症，是由这些酶的基因突变引起的。该项目的具体目标是表征遗传模式植物拟南芥At 1g 33320位点编码的基因的酶功能和生理作用。基于序列同源性，提出该基因编码胱硫醚γ-合酶，一种碳氧裂解酶。然而，初步证据表明，它的功能是胱硫醚β-裂解酶，一种碳硫连接酶。将通过进行体外酶动力学实验，并通过使用遗传互补试验在体内条件下检查酶的功能来检验该假设。基因产物的生理作用也将通过研究其表达、其亚细胞定位以及通过检查基因敲除突变所导致的表型来探索。

DESCRIPTION (provided by applicant): The broad, long-term objective of the project is to understand the structure and function relationship of enzymes that catalyze reactions around cystathione, a central intermediate in the trans-sulfuration pathways that inter-convert cysteine and homocysteine. The trans-sulfuration enzymes play important roles in supplying cysteine and methionine for growth and in regulating the homeostasis of these amino acids. Certain genetic diseases in humans, such as homocysteinemia, are caused by mutations in the genes for these enzymes.The specific aim of project is to characterize the enzymatic function and physiological role of a gene encoded by locus At1g33320 of the genetic model plant Arabidopsis thaliana. Based on sequence homology this gene was proposed to encode cystathionine gamma-synthase, a carbon-oxygen lyase. However, preliminary evidence suggests that it functions as cystathionine beta-lyase, a carbon-sulfur tyase. This hypothesis will be examined by carrying out in vitro enzyme kinetic experiments, and by examining the function of the enzyme under in vivo conditions using a genetic complementation test. The physiological role of the gene product will also be explored by studying its expression, its subcellular localization, and by examining the phenotype resulting from knock-out mutation of the gene.