Deoxyribonucleotide triphosphates dNTP

Four deoxyribonucleotide triphosphates (dNTP s) are required for DNA synthesis (note the only difference between deoxyribonucleotides and ribonucleotides is the absence of an OH group at position 2 on the ribose ring). These are dATP, dGTP, dTTP and dCTP. The high energy phosphate bond between the a and (3 phosphates is cleaved and the deoxynucleotide monophosphate is incorporated into the new DNA strand. 

They check the size of an incoming deoxyribonucleotide triphosphate (dNTP) to help insure that the correct, complementary choice is made. 

New DNA strands are synthesized in the 5 —>3 direction. This means that new deoxyribonucleotide triphosphates (dNTPs) are added onto the 3 -OH of the growing chain in a template-directed maimer by DNA polymerase. The polymerization involves the formation of a phosphodiester bond between the a-phosphate of the incoming nucleotide and the 3 -OH of the nascent chain. Only the deoxyribonucleotide monophosphate (dNMP) is incorporated into the growing chain the pyrophosphate (PPi) is cleaved off during polymerization. The cleavage of the phosphodiester bond provides the energy for the polymerization reaction. The resulting pyrophosphate ion is rapidly hydrolyzed to two phosphate ions by the ubiquitous and abundant enzyme pyrophosphatase, and this reaction drives the polymerization in the direction of polymer formation (Fig. 8-1). 

ALL, acute lymphoblastic leukemia AML, acute myelogenous leukemia CLL, chronic lymphocytic leukemia CML, chronic myelogenous leukemia DHFR, dihydrofolate reductase dNTP, deoxyribonucleotide triphosphate FdUTP, 5-fluorodeoxyuridine-5 -triphosphate FUTP, 5-fluorouridine-5 -triphosphate TS, thymidine synthase. 

The reactants are deoxyribonucleotide triphosphates. They provide not only the moiety to be inserted (the deoxyribonucleotide) but also the energy to drive the reaction (dNTP inserted NMP + PP., PP. 2Pj). 

E The combined exonuclease and polymerase activities of T4 DNA polymerase are exploited in the O Farrell method for the general labeling of double-stranded DNA. dNTP = deoxyribonucleotide triphosphate. 

Among a large number of natural inhibitors of mammalian DNA polymerase, the inhibition by epigallocatechin-3-gallate was competitive with respect to the DNA template-primer and noncompetitive with respect to the 2 -deoxyribonucleotide 5 -triphosphate (dNTP) substrate (Mizushina et al, 2005). Glucopyranosides of kaempferol and quercetin also specifically bind DNA polymerase in vitro, but their action in vivo is not yet proved (Mizushina et al, 2003). 

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