Physiological concentrations of purines and pyrimidines

The concentrations of bases, nucleosides, and nucleosides mono-, di- and tri-phosphate are compared for about 600 published values. The data are predominantly from mammalian cells and fluids. For the most important ribonucleotides average concentrations ±SD (M) are: ATP, 3,152±1,698; GTP, 468±224; UTP, 567±460 and CTP, 278±242. For deoxynucleosidestriphosphate (dNTP), the concentrations in dividing cells are: dATP, 24±22; dGTP, 5.2±4.5; dCTP, 29±19 and dTTP 37±30. By comparison, dUTP is usually about 0.2 M. For, the 4 dNTPs, tumor cells have concentrations of 6–11 fold over normal cells, and for the 4 NTPs, tumor cells also have concentrations 1.2–5 fold over the normal cells. By comparison, the concentrations of NTPs are significantly lower in various types of blood cells. The average concentration of bases and nucleosides in plasma and other extracellular fluids is generally in the range of 0.4–6 M; these values are usually lower than corresponding intracellular concentrations. For phosphate compounds, average cellular concentrations are: P_i, 4400; ribose-1-P, 55; ribose-5-P, 70 and P-ribose-PP, 9.0. The metal ion magnesium, important for coordinating phosphates in nucleotides, has values (mM) of: free Mg²⁺, 1.1; complexed-Mg, 8.0. Consideration of experiments on the intracellular compartmentation of nucleotides shows support for this process between the cytoplasm and mitochondria, but not between the cytoplasm and the nucleus.     

Degradation of purines and pyrimidines by microorganisms

[This corrects the article on p. 403 in vol. 40.].     

Influence of purines and pyrimidines on cold hardiness of plants. V. Uptake and translocation of purines and pyrimidines in alfalfa

Differential uptake of radioactive purines and pyrimidines by alfalfa leaves was observed. Translocation of radioactive constituents from leaves to stem-crown or root tissues (metabolic sinks) was not proportional to uptake. After 40 days of hardening at low temperatures, ranking of radioactivity levels changed for the base treatments and the change in leaves was different from that in whole plants. Ratios calculated for radioactivity from guanine and cytosine/adenine and uracil for RNA of leaves was twice as large as that for stem-crown or root tissues.More than $\text{3}\text{4}$ of the total radioactivity was found in soluble cytoplasm, although less than 10% of the RNA of hardened plants has been found in this fraction. This has special significance because soluble cytoplasm is the fraction that contains most of the polynucleotide phosphorylase activity and contains 60% of the soluble proteins that have been closely associated with cold tolerance.     

疾病干预的新靶点:嘌呤与嘧啶受体

内源性核苷、核苷酸通过嘌呤与嘧啶受体(P受体),参与机体组织器官多种功能的调节。在肿瘤、细胞凋亡、局部缺血、伤口愈合、骨质疏松、药物毒性、炎症及痛觉等病理状态下,P受体的内源性配体核苷与核苷酸发挥保护作用,P1、P2受体及其受体亚型的选择性激动剂和桔抗剂具有宽广的临床应用前景。     

Phosphorus-containing purines and pyrimidines: A new class of transition state analogs

Synthetic routes to the [1,5,2]-diazaphosphorine (“4-phosphapyrimidine”), imidazo[4,5-e][1,5,2]-diazaphosphorine (“6-phosphapurine”), and imidazo[4,5-d][1,3,2]-diazaphosphorine (“2-phosphapurine”) ring systems have been developed. Appropriately functionalized derivatives of these heterocycles are desired as possible transition state analogs of the nucleoside deaminases.