Mechanisms of glutamate dehydrogenase allostery

描述（由申请人提供）：谷氨酸脱氢酶（GDH）是一种存在于所有生物体中的古老酶。由该酶催化的谷氨酸可逆氧化脱胺反应生成2-氧戊二酸盐的基本化学过程一直保持不变。然而，来自动物王国的GDH受大量化合物的变构调节，而来自其他王国的酶则完全不受调节。通过我们的个人和合作努力，我们已经确定了动物GDH与这些变构调节因子中的几种复合物的结构，并建立了变构是如何产生的模型。我们还通过发现影响GTP抑制的突变是儿童高胰岛素血症/高氨血症（HI/HA）综合征的根本原因，证明了GDH调节的重要性。此外，我们已经证明GDH参与正常胰腺组织中葡萄糖和亮氨酸刺激的胰岛素分泌。我们认为这种胰岛素稳态的调节是由于gdh介导的细胞内信号分子谷氨酰胺的控制。

DESCRIPTION (provided by applicant): Glutamate dehydrogenase (GDH) is an ancient enzyme found in all living organisms. The underlying chemistry of the reversible oxidative deamination of glutamate to 2-oxoglutarate catalyzed by this enzyme has remained unchanged through the epochs. However, GDH from the animal kingdom is allosterically regulated by a large number compounds while the enzyme from other kingdoms is completely unregulated. Through our individual and collaborative efforts, we have determined the structures of animal GDH complexed with several of these allosteric regulators and have models for how allostery is exacted. We have also shown the importance of GDH regulation by our finding that mutations that affect GTP inhibition are the root cause of the hyperinsulinism/hyperammonemia (HI/HA) syndrome in children. Furthermore, we have shown that GDH is involved in both glucose and leucine stimulated secretion of insulin from normal pancreatic tissue. We propose that this regulation of insulin homeostasis is due to GDH-mediated control of the intracellular signaling molecule, glutamine. It is therefore apparent that understanding the allosteric regulation of GDH is crucial to understanding insulin homeostasis. To that end, this proposal aims to use a combination of techniques to understand where these various regulators bind and how they modulate enzymatic activity. We will also further analyze some HI/HA mutants to better understand the pathology of this life-threatening disorder. Perhaps most exciting is that we have leveraged our understanding of GDH to discover a family of new, non-toxic compounds that act via GDH and can potentially treat both HI/HA and type II diabetes. Finally, we have shown that the GDH from Ciliates is an evolutionary 'missing link' between animals and the other kingdoms. By further studying this form of GDH we will elucidate animal allostery by better understanding how and why it evolved. Together, these studies will not only answer fundamental questions as to how protein subunits communicate with each other during allostery but will solidify our hypothesis that allosteric regulation of GDH plays a critical role in insulin homeostasis.