HEPATIC GLUTAMINASE

谷氨酰胺在所有哺乳动物细胞中起着重要的生物合成作用。 谷氨酰胺在糖尿病期间由肝脏使用，在糖尿病期间由肾脏使用。 代谢性酸中毒和哺乳期乳腺，它也是一种 许多快速分裂的细胞（包括癌症）的主要呼吸燃料 细胞 哺乳动物组织中谷氨酰胺催化剂的主要酶 是磷酸活化转氨酶的两种同工酶。 肝脏类型是 只在成人肝脏中发现，而另一种酶（肾型） 在所有其他谷氨酰胺利用组织中发现，包括胎肝和 肝癌细胞 所述工作的目的是表征和 了解磷酸活化谷氨酰胺酶的作用和调节 鼠肝 这项工作源于对肝转氨酶活性的观察， 在链脲佐菌素糖尿病期间增加了4倍。 该酶已被 纯化的，针对它的特异性抗体，并用于识别 推定的cDNA。 cDNA的鉴定将通过比较来证实 的DNA和氨基酸序列，杂交选择的mRNA和 融合肽的分析。 cDNA将用于确定 mRNA的相对丰度和转录率 对照组和糖尿病大鼠肝脏中的转氨酶基因。 细胞外 参与调节肝转氨酶基因表达的刺激物 将使用分离的肝细胞和肝癌细胞进行鉴定。 该cDNA将用于鉴定编码肝型 谷氨酰胺酶和其它谷氨酰胺利用酶。 的分布 肝和肾型转氨酶（活性、蛋白质和mRNA）将被 在不同的肝癌细胞和大鼠肝脏中， 发展阶段 将在细胞中分析染色质结构 显示两个基因的差异表达。 这些系统提供了 研究组织特异性、激素和发育的独特模型 转氨酶基因表达的调控。 结果将提供 为什么有两种酶以及它们的功能 存在于不同的细胞类型中。

Glutamine plays an important biosynthetic role in all mammalian cells. Glutamine is used by the liver during diabetes, the kidney during metabolic acidosis and the mammary gland during lactation, it is also a major respiratory fuel for many rapidly dividing cells including cancer cells. The major enzymes of glutamine catabolism in mammalian tissues are two isozymes of phosphate activated glutaminase. The liver type is found exclusively in adult liver while the other enzyme (kidney-type) is found in all other glutamine utilizing tissues, including fetal liver and hepatoma cells. The aim of the work described is to characterize and understand the role and regulation of phosphate activated glutaminase in rat liver. This work stems from the observation that hepatic glutaminase activity is increased 4-fold during streptozotocin diabetes. The enzyme has been purified, specific antibodies raised against it and used to identify a putative cDNA. The identify of the cDNA will be confirmed by comparison of the DNA and amino acid sequences, hybrid selection of mRNA and analysis of fusion peptide. The cDNA will be used to determine the relative abundance of mRNA and the rate of transcription hepatic glutaminase gene in liver from control and diabetic rats. Extracellular stimuli involved in the regulation of hepatic glutaminase gene expression will be identified using isolated hepatocytes and hepatoma cells. The cDNA will be used to identify genomic sequences encoding liver-type glutaminase and other glutamine utilizing enzymes. The distribution of liver- and kidney-type glutaminase (activity, protein and mRNA) will be determined in different hepatoma cells and in rat liver at different stages of development. Chromatin structure will be analyzed in cells showing differential expression of the two genes. These systems offer a unique model for the study of tissue-specific, hormonal and developmental regulation of glutaminase gene expression. The results will provide valuable insights into why there are two enzymes and what their functions are in the different cell types.