Uracil deoxyriboside

Fig. 11.1.3. Reversed phase HPLC of nucleic acid bases and nucleosides. Chromatographic conditions column, Spherisorb ODS-2, 5 pm (250 x 4.6 mm) mobile phase, 0.05 M monobasic ammonium phosphate, pH 3.5 flow rate, 1.5 ml/min temperature, ambient detection, UV at 260 nm. Peaks C, cytosine U, uracil FU, fluorouracil CR, cytosine riboside A, adenine CdR, cytosine deoxyriboside UR, uracil riboside T, thymine FUR, fluorouracil riboside UdR, uracil deoxyriboside, FUdR, fluorouracil deoxyriboside GR, guanine riboside GdR, guanosine deoxyriboside TdR, thymine deoxyriboside AR, adenine riboside. Reproduced from Miller et al. (1982), with...

Uracil, or 2,6-dihydroxypyrimidine, was discovered in 1901 in yeast nucleic acids, and its structure was established by Fisher s organic methods. Uracil is a universal constituent of ribonucleic acids. In general, it is absent from DNA, although some bacterial DNA s have been reported to contain small amounts of uracil deoxyribosides. Cytosine, or 2-hydroxy-6-aminopyrimidine, was discovered in 1894 by Kassel and Newman. Except for the T-even bacteriophages, all DNA and RNA specimens in which the pyrimidine has been characterized contain cytosine. 

Adenine -I- uracil deoxyriboside uracil -f adenine deoxyriboside (23)... 

The most important pyrimidine derivatives are those upon which biological organisms depend. Cytosine 1018 and uracil 1019 are found in ribonucleic acid (RNA) in the form of their ribonucleotides, cytidine 1020 and uridine 1021, while in deoxyribonucleic acid (DNA), cytosine and thymine 1022 are found in the form of their 2 -deoxyribonucleotides, 2 -deoxycytidine 1023 and thymidine 1024. 5-Methylcytosine 1025 is also found to a small extent (c. 5%) in human DNA in the form of its 2 -deoxyriboside 1026, and 5-(hydroxymethyl)cytosine-2 -deoxyriboside 1027 has also been detected in smaller amounts <2005CBI1>. Many variants of cytosine and uracil can be found in RNA including orotic acid 1028 in the form of its ribonucleotide orotidine 1029. Other pyrimidine derivatives to have been isolated from various biological sources include 2 -deoxyuridine 1030, alloxan 1031, and toxopyrimidine (pyramine) 1032 (Figure 2). 

The 5-chloro, 5-bromo and 5-iodo derivatives of uracil are base analogues of thymine and, in cellular systems, can replace the latter in DNA u >. Furthermore, 5-iodo-2 -deoxyuridine is an antiherpes agent currently used for treatment of ocular herpes keratitis. By contrast, 5-fluorouracil can replace uracil in RNA, and, together with 5-fluoro-2 -deoxyuridine, is employed in tumour chemotherapy. All the foregoing are also known mutagens, and 5-bromouracil and its deoxyriboside are widely employed in studies on mutagenesis U9). 

SYNS DEOXYFLUOROURIDINE l-p-d-2 -DEOXYRIBOFURANOSYL-5-FLUOROURACIL FDUR FLOXURIDIN FLOXURIDINE FLUORODEOXY-URIDINE p-5-FLUORO-2 -DEOXYURIDINE 5-FLUORODEOXYURIDINE 5-FLUORO-2-DEOXY-URIDINE 5-FLUORO-2 -DEOXYURIDINE 5-FLUOROURACIL DEOXYRIBOSIDE 5-FLUORO-URACIL-2 -DE0XYRIB0SIDE FLUORURIDINE DEOXYRIBOSE FUDR 5-FUDR NSC-27640 RO 5-0360... 

Fig. 11.1.4. Separation of uracil and 5-fluorouracil bases, nucleosides and nucleotides by reversed phase ion-pair HPLC. Chromatographic conditions column, Bondapak Cig (300 x 4 mm) mobile phase, (from 0-30 min) 0.1 mM tetrabutylammonium hydrogen sulphate (Cjg), 2.5 mM tetraethylammonium bromide (Cg) and 2% methanol in 2 mM sodium acetate, 1.5 mM phosphate buffer, pH 6.0 (Buffer A) (from 30-50 min) Buffer A-i-30 mM phosphate detection, UV at 254 nm. Peaks FU, fluorouracil FUR, fluorouracU riboside/ FUdR, fluorouracil deoxyriboside FUMP, fluorouridine 5 -monophosphate 5 dFUR, 5 -deoxyfluorouracil riboside FdUMP, deoxyfluorouri-dine monophosphate UDPG, uridine diphosphoglucose UDP, uridine diphosphate dUDP, deoxyuridine monophosphate UTP, uridine triphosphate. Reproduced from Au et al. (1982), with permission.

However, for adenine, guanine, and uracil, the dominant route of anabolism is by way of their ribonucleotide derivatives and traffic along the deoxyribosidic route is not ordinarily significant. Because cytosine is not a substrate for nucleoside phosphorylases, incorporation by the phos-phorylase-kinase route is not possible for this base. The other pyrimidine base of DNA, thymine, is poorly anabolized by both animal and bacterial cells, in spite of the fact that most cells possess thymidine phosphorylase, the action of which is readily reversible. This suggests that ordinarily cellular supplies of deoxyribose 1-phosphate are not available for base anabolism. Experiments are cited below in which it was demonstrated that a significant contribution to the biogenesis of deoxyribose of DNA in E. colt cells did not occur by a route other than ribonucleotide reduction. 

Thymidine is formed by methylation of the carbon 5 of uracil. In vivo experiments demonstrated that the methyl donor is either formate or the beta-carbon of serine. The conversion of uracil to thymidine in vitro was first demonstrated using bone marrow or embryo cell suspensions. Three main points were established (1) the deoxyriboside of the 2[ " C]uracil is in their system incorporated into DNA (2) the incorporation... 

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