The article by Thomas W. Traut from the Department of Biochemistry and Biophysics at the University of North Carolina School of Medicine reviews the physiological concentrations of purines and pyrimidines, including their bases, nucleosides, and nucleoside mono-, di-, and tri-phosphates. The data, primarily from mammalian cells and fluids, are compared for about 600 published values. Key findings include: - **Ribonucleotides**: ATP (3,152 ± 1,698 μM), GTP (468 ± 224 μM), UTP (567 ± 460 μM), and CTP (278 ± 242 μM). - **Deoxynucleoside triphosphates (dNTPs)**: dATP (24 ± 22 μM), dGTP (5.2 ± 4.5 μM), dCTP (29 ± 19 μM), and dTTP (37 ± 30 μM). dUTP is typically about 0.2 μM. - **Tumor cells** have 6–11 fold higher concentrations of dNTPs and 1.2–5 fold higher concentrations of NTPs compared to normal cells. - **Plasma and extracellular fluids**: Bases and nucleosides generally range from 0.4–6 μM, lower than intracellular concentrations. - **Phosphate compounds**: P1 (4400 μM), ribose-1-P (55 μM), ribose-5-P (70 μM), and P-ribose-PP (9.0 μM). - **Magnesium ion**: Free Mg2+ (1.1 mM) and complexed Mg (8.0 mM). The study also supports the intracellular compartmentation of nucleotides between the cytoplasm and mitochondria but not between the cytoplasm and the nucleus. The importance of these concentrations is highlighted in pharmacology and enzyme characterization.The article by Thomas W. Traut from the Department of Biochemistry and Biophysics at the University of North Carolina School of Medicine reviews the physiological concentrations of purines and pyrimidines, including their bases, nucleosides, and nucleoside mono-, di-, and tri-phosphates. The data, primarily from mammalian cells and fluids, are compared for about 600 published values. Key findings include: - **Ribonucleotides**: ATP (3,152 ± 1,698 μM), GTP (468 ± 224 μM), UTP (567 ± 460 μM), and CTP (278 ± 242 μM). - **Deoxynucleoside triphosphates (dNTPs)**: dATP (24 ± 22 μM), dGTP (5.2 ± 4.5 μM), dCTP (29 ± 19 μM), and dTTP (37 ± 30 μM). dUTP is typically about 0.2 μM. - **Tumor cells** have 6–11 fold higher concentrations of dNTPs and 1.2–5 fold higher concentrations of NTPs compared to normal cells. - **Plasma and extracellular fluids**: Bases and nucleosides generally range from 0.4–6 μM, lower than intracellular concentrations. - **Phosphate compounds**: P1 (4400 μM), ribose-1-P (55 μM), ribose-5-P (70 μM), and P-ribose-PP (9.0 μM). - **Magnesium ion**: Free Mg2+ (1.1 mM) and complexed Mg (8.0 mM). The study also supports the intracellular compartmentation of nucleotides between the cytoplasm and mitochondria but not between the cytoplasm and the nucleus. The importance of these concentrations is highlighted in pharmacology and enzyme characterization.