Deoxynucleoside 5 -monophosphate

In the diester method a deoxynucleoside-5 -monophosphate is condensed with the 3 -OH group of a deoxynucleotide to produce a 3, 5 -phosphodiester. This is illustrated by a general method for dinucleotide synthesis developed by H.G. Khorana (K.L. Agarwal, 1976). One N-... 

This enzyme [EC 2.7.1.77] catalyzes the reaction of a nucleotide with a 2 -deoxynucleoside to produce a nucleoside and a 2 -deoxynucleoside 5 -monophosphate. The nucleotide substrate can be substituted with phenyl phosphate and nucleoside 3 -phosphates, although they are not as effective. 

NUCLEOSIDE PHOSPHOTRANSFERASE 2 -Deoxynucleoside 5 -monophosphate, NUCLEOSIDE PHOSPHOTRANSFERASE (DEOXY)NUCLEOSIDE MONOPHOSPHATE KINASE... 

Finally, it should be noted that exonuclease III possesses an intrinsic DNA-phosphatase activity which specifically removes 3 -phosphoryl groups from double-stranded polynucleotides. This enzyme when acting on a 3 -phosphoryl-terminated DNA, first removes the 3 -phosphoryl group as inorganic phosphate, then proceeds as an exonuclease with the stepwise release of deoxynucleoside 5 -monophosphates (9). 

To grow and divide, cancer cells must duplicate their chromosomes which are composed of deoxynucleoside 5 monophosphates (dNMPs) polymerized in unique sequences. Cancers may differ from normal cells of the body by growing more rapidly and/or by cycling and dividing continuously. Inhibitors of nucleotide biosynthesis will have selective toxicity for such cancers due to a depletion or imbalance in the cellular levels of dNTPs required for DNA synthesis, which would be more pronounced than in normal cells. A selective depletion of one of the four dNTPs (e.g., dTTP) by treatment of cancer... 

Treatment of nucleoside and deoxynucleoside 5 -monophosphates with inorganic diphosphonate in aquo at pH 6 at elevated temperatures has been reported to afford the corresponding 5 -phosphonylphosphates (112) in yields of up to 70 xhe compounds were characterized largely using 3lp n.m.r. spectroscopy. 

Like many other enzymes, DNA polymerase exhibits different catalytic properties. As mentioned previously, it catalyzes the polymerization of monodeox-ynucleotide triphosphate to yield DNA. In a reaction that is the reverse of the polymerase reaction, DNA polymerase can cleave DNA pyrophosphorolytically to yield the four deoxynucleotide triphosphates. The enzyme can hydrolyze quantitatively native or denatured DNA, synthetic polymers, and oligonucleotides to yield deoxynucleoside-5-monophosphate. 

Griffith, T.J. Helleiner, C.W. The partial purification of deoxynucleoside monophosphate kinases from L cells. Biochim. Biophys. Acta, 108, 114-124 (1965)... 

Other useful targets for pharmaceutical agents are thymidylate synthase and dihydrofolate reductase, enzymes that provide the only cellular pathway for thymine synthesis (Fig. 22-49). One inhibitor that acts on thymidylate synthase, fluorouracil, is an important chemotherapeutic agent. Fluorouracil itself is not the enzyme inhibitor. In the cell, salvage pathways convert it to the deoxynucleoside monophosphate FdUMP, which binds to and inactivates the enzyme. Inhibition by FdUMP (Fig. 22-50) is a classic example of mechanism-based enzyme inactivation. Another prominent chemotherapeutic agent, methotrexate, is an inhibitor of dihydrofolate reductase. This folate analog acts as a competitive inhibitor the enzyme binds methotrexate with about 100 times higher affinity than dihydrofolate. Aminopterin is a related compound that acts similarly. 

Figure 14.1 The four deoxynucleoside monophosphates that constitute DNA.

DNA polymerases have just one binding site for all four combinations of base pairing—AT, TA, GC, and CG. The specificity of these sites is dictated by the Watson-Crick pairing rules, in that the sites themselves appear to recognize just the overall shape of a correct purine-pyrimidine pair, with the precise specificity resulting from the complementary nature of the base pairing. The polymerase catalyzes the transfer of a complementary deoxynucleoside monophosphate from its triphosphate to the 3 -hydroxyl of the primer terminus (equation 14.1). 

There is an alternative method of generating cohesive tails. The enzyme calf thymus terminal (deoxynucleotidyl) transferase adds deoxynucleoside monophosphate residues from 5 -deoxynucleoside triphosphates to protruding 3 -hydroxyl termini in the absence of a template. For example, as shown in equations 14.5 to 14.7,... 

List the chemical shift assignments for the free deoxynucleoside monophosphates (dNMP) and their Pt(II) bound adducts in Table 6.4. 

Nucleic acid is the general name for the macromolecules RNA and DNA. They are each made up of a polymer of nucleoside monophosphates or deoxynucleoside monophosphates, respectively, with the 5 phosphate of each group forming a phosphodiester bond with the 3 hydroxyl of the subsequent group (Figure 4.1)... 

The existence of kinases which convert deoxyribonucleoside monophosphates to their triphosphates has been recognized for a considerable time. For example, Komberg and his co-workers 30), in their pioneering experiments with DNA polymerase, used enzymatically prepared triphosphates labeled in the a-phosphate enzyme preparations partly purified from E. coii extracts were employed to convert o- P-labeled deoxynucleoside monophosphates to the ct-Iabeled triphosphates. 

Another instance of the induction of enzymes not ordinarily present in E. coli which occurs upon infection with bacteriophage T2 (see Section I, D and II, E) is found in the work of Bello and Bessman ( 4), who isolated from T2-infected E. coli, a deoxynucleoside monophosphate kinase with specificities quite distinct from those of the kinases discussed above. The phage-induced kinase is specific for deoxj/ribonucleoside monophosphates and will phosphorylate three of the four nucleotides destined for phage DNA deoxyguanylate, thymidylate, and hydroxymethyldeoxycyti-dylate. The enzyme does not phosphorylate deoxyadenylate. 

The applications of electrospray (ion spray)-m.s. continue to broaden and have, this year, found utility for the identification of glycoprotein and glycopeptide firagments produced by enzymatic digestion.26 Regioisomeric esters of sucrose (e.g. 6-O-octanoyl and 6 -< -octanoyl) have been characterized by electrospray tandem m.s. Electrospray mass q>ectra for selected modified deoxynucleosides and deoxynucleoside monophosphates have been determined, and methods for intensity enhancement of MH described MH may be detected with as little as 3 pmol of substrate. ... 

All NRTIs, as exemplified for AZT (Fig. 7), act in a similar fashion following their uptake by the cells, they are phosphorylated successively to their 5 -monophosphate, 5 -diphosphate, and 5 -triphosphate form (De Clercq 2002). Unlike the first phosphorylation step in the metabolic pathway of the acyclic guanosine analogues (see above), which is carried out by a virus-encoded enzyme (thymidine kinase), the first as well as the subsequent phosphorylations of the 2, 3 -dideoxynucleosides are carried out by cellular enzymes, that is, a 2 -deoxynucleoside (e.g., dThd) kinase, a 2 -deoxynucleotide (e.g., dTMP) kinase, and a (2 -deoxy)nucleoside 5 -diphosphate (NDP) kinase. 

An example is given in Fig. 1, where normalized total fluorescence decays are shown for 2 -deoxynucleosides and 2 -deoxynucleotides. In contrast to previous findings our work revealed that the fluorescence decays are complex and cannot be described by single exponentials. They consist of an ultrafast component (< 200 fs) and a slower one (ranging from about 0.4 ps for 2 -deoxyadenosine up to 1.4 ps in the case of 2 -deoxycytidine monophosphate). 

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