Deoxynucleoside monophosphates

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. ... 

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