ROLE OF THE SALVAGE REACTIONS IN THE REGULATION OF PURINE METABOLISM

挽救反应在嘌呤代谢调节中的作用

• 批准号: 4687714
• 负责人: R L VEECH
• 金额: --
• 依托单位: NATIONAL INSTITUTE ON ALCOHOL ABUSE AND ALCOHOLISM
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/4687714
• 关键词: 5' nucleotidase; high performance liquid chromatography; liver cells; liver metabolism; nucleic acid metabolism; nucleobase; nucleoside ribosyltransferase; phosphates; purine /pyrimidine metabolism; purine nucleoside phosphorylase; purine nucleosides; purine nucleotides; pyrimidine nucleosides; pyrimidine nucleotides; pyrophosphates; ribose phosphate; urate

This project compared thermodynamic data obtained in vitro for the purine salvage reactions to the measured steady-state levels of purine and pyrimidine nucleobases, nucleosides, nucleotides, and related cofactor compounds in vivo. (The hypothesis is that the purine salvage enzymes catalyze reactions that approach near-equilibrium, in vivo, and thus that rates of synthesis of the necessary cofactors such as ribose 1-phosphate (R1-P), phosphoribosylpyrophosphate (PRPP), inorganic phosphate (Pi), and inorganic pyrophosphate (PPi), could profoundly influence the relative amounts of free bases and nucleosides available for nucleotide and urate production.) Current methods for the extraction and quantitation of purine and pyrimidine nucleobases and nucleosides as well as for R1-P and PRPP are suspect and have led to confusion and posibly misinterpretation of scientific data. Therefore, we began by attempting to improve on current methods for measuring the aforementioned metabolites in liver extracts. A superior high-performance liquid chromatograhic procedure was developed for measuring purine and pyrimidine nucleo bases and nucleosides in rat hepatocytes. Progress was also made on improving techniques for the extraction and quantitation of R1-P and PRPP. The apparent equilibrium constants for the purine salvage reactions catalyzed by purine nucleoside phosphorylase were completed as well as for the ancillary reactions, phosphoribomutase and 5' nucleotidase. The equilibrium constant for the phosphoribosyltransferases will be completed once PRPP can be measured. Once these in vivo measurements are made it can be determined whether the salvage reactions approach near-equilibrium in vivo and, if so, whether it will be possible to assess the influence of fluctuations in the magnitude of the cofactor couples PRPP/PPi and R1-P/Pi on the rates of nucleotide, nucleic acid, and uric acid synthesis in a variety of cell types.

该项目比较了嘌呤在体外获得的热力学数据 对测得的嘌呤稳态水平的打捞反应， 嘧啶核苷酶，核苷，核苷酸和相关辅因子 体内化合物。 （假设是嘌呤打捞酶 催化接近平衡的反应，体内，因此 必要的辅助因子（如核糖1-磷酸盐）的合成速率 （R1-P），磷酸磷酸磷酸盐（PRPP），无机磷酸盐（PI）和 无机焦磷酸盐（PPI）可以深刻影响相对 可用于核苷酸和尿酸盐的自由碱和核苷量 生产。） 当前提取和定量嘌呤和定量的方法 嘧啶核苷酶和核苷以及R1-P和PRPP为 可疑并导致了混乱，明显地误解了 科学数据。 因此，我们首先试图改善当前 测量肝脏提取物中上述代谢产物的方法。 一个 开发了出色的高性能液态色谱程序 测量大鼠的嘌呤和嘧啶核碱和核苷 肝细胞。 在改进技术方面也取得了进步 R1-P和PRPP的提取和定量。 嘌呤挽救反应的明显平衡常数 通过嘌呤核苷磷酸化酶催化的以及 辅助反应，磷脂酶和5'核苷酸酶。 这 磷酸贝糖基转移酶的平衡常数将完成 一旦可以测量PRPP。 一旦进行了这些体内测量，就可以 可以确定打捞反应是否接近平衡 体内以及是否有可能评估 辅因子夫妇PRPP/PPI和R1-P/PI的大小波动 关于核苷酸，核酸和尿酸合成的速率 各种细胞类型。