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Purine deoxyribonucleotides

V.V. Zakjevskii et al., Electron propagator studies of vertical electron detachment energies and isomerism in purinic deoxyribonucleotides. Int. J. Quantum Chem. 107, 2266-2273 (2007)... [Pg.17]

Purine deoxyribonucleotides are derived primarily from the respective ribonucleotide (Fig. 6.2). Intracellular concentrations of deoxyribonucleotides are very low compared to ribonucleotides usually about 1% that of ribonucleotides. Synthesis of deoxyribonucleotides is by enzymatic reduction of ribonucleotide-diphosphates by ribonucleotide reductase. One enzyme catalyzes the conversion of both purine and pyrimidine ribonucleotides and is subject to a complex control mechanism in which an excess of one deoxyribonucleotide compound inhibits the reduction of other ribonucleotides. Whereas the levels of the other enzymes involved with purine and pyrimidine metabolism remain relatively constant through the cell cycle, ribonucleotide reductase level changes with the cell cycle. The concentration of ribonucleotide reductase is very low in the cell except during S-phase when DNA is synthesized. While enzymatic pathways, such as kinases, exist for the salvage of pre-existing deoxyribosyl compounds, nearly all cells depend on the reduction of ribonucleotides for their deoxyribonucleotide... [Pg.91]

S Additional information <3, 7> (<3> enzyme exists in different conformational states with different substrate kinetic properties [9] <3> presumably one common nucleoside acceptor site [15] <3> purine deoxynucleo-side activity inseparably associated with deoxycytidine kinase protein [16] <3> several isozymes cytosolic deoxycytidine kinase I and II, plus mitochondrial isozyme [10] <3> multisubstrate enzyme, that also phos-phorylates purine deoxyribonucleotides [9] <7> enzyme has two separate active sites for deoxycytidine and deoxyadenosine activity [22] <3> reacts with both enantiomers of -deoxycytidine, -deoxyguanidine, -deoxyadenosine, and a-D-deoxycytidine is also substrate [31] <3> reacts with both enantiomers of jS-deoxyadenosine, j3-arabinofuranosyl-adenine and jd-deoxyguanine ]34] <3> remarkably relaxed enantioselectivity with respect to cytidine derivatives in p configuration [36] <3> lack of enantioselectivity for D- and L-analogues of cytidine and adenosine [43]) [9, 10, 15, 16, 22, 31, 34, 43]... [Pg.241]

At the nucleotide level, the metabolism of purine deoxyribonucleotides is uncomplicated adenine and guanine deoxyribonucleotides are not interconverted, and hydrolysis or transfer reactions involving phosphoryl groups are the only major transformations known. [Pg.206]

Figure 34-6. Regulation of the reduction of purine and pyrimidine ribonucleotides to their respective 2 -deoxyribonucleotides. Solid lines represent chemical flow. Broken lines show negative ( ) or positive ( ) feedback regulation. Figure 34-6. Regulation of the reduction of purine and pyrimidine ribonucleotides to their respective 2 -deoxyribonucleotides. Solid lines represent chemical flow. Broken lines show negative ( ) or positive ( ) feedback regulation.
Deoxyribonucleotides A purine or pyrimidine base bonded to a deoxyribose containing a... [Pg.65]

The two classes of nucleotide that must be synthesised are the pyrimidine and purine ribonucleotides for RNA synthesis and the deoxyribonucleotides for DNA synthesis. For the original sources of the nitrogen atoms in the bases of the pyrimidine and purine nucleotides, see Figure 20.7. The pathway for the synthesis of the pyrimidine nucleotides is... [Pg.455]

These transcription factors activate genes that express the enzymes for purine and pyrimidine deoxyribonucleotide synthesis and DNA duplication. [Pg.476]

DNA is a linear polymer of deoxyribonucleotides in which the sequence of purine and pyrimidine bases encodes cellular RNA and protein molecules. [Pg.151]

The sugar component in RNA is ribose, whereas in DNA it is 2-dexoyribose. In deoxyribonucleotides, the heterocyclic bases are purine bases, adenine and guanine, and pyrimidine bases, cytosine and thymine. In ribonucleotides, adenine, guanine and cytosine are present, but not thymine, which is replaced by uracil, another pyrimidine base. [Pg.170]

Fig. 1. Consisting of two helically intertwined strands, ihe DNA molecule is composed of dcoxyribose and phosphate. As shown here, at periodic intervals the sugar-phosphate backbones are joined together by the complementary purine and pyrimidine bases. A single base linked to a deoxyribose-pbosphate moiety constitutes a deoxyribonucleotide. Legend Solid black circles — Thymine Vertical bars = Adenine Horizontal bars = Guanine Dotted circles = Cytosine... Fig. 1. Consisting of two helically intertwined strands, ihe DNA molecule is composed of dcoxyribose and phosphate. As shown here, at periodic intervals the sugar-phosphate backbones are joined together by the complementary purine and pyrimidine bases. A single base linked to a deoxyribose-pbosphate moiety constitutes a deoxyribonucleotide. Legend Solid black circles — Thymine Vertical bars = Adenine Horizontal bars = Guanine Dotted circles = Cytosine...
Purine Biosynthesis Is Regulated at Two Levels Pyrimidine Biosynthesis Is Regulated at the Level of Carbamoyl Aspartate Formation Deoxyribonucleotide Synthesis Is Regulated by Both Activators and Inhibitors... [Pg.533]

The pentose component of naturally occurring nucleotides is ribose or 2-deoxyribose (i.e., ribose with a hydrogen instead of a C-2 —OH). In nucleotides the purine or pyrimidine is attached to C-1 of the pentose in the /3 configuration. This means that the base is cis relative to C-5 —OH and trans relative to the C-3 —OH. The major function of deoxyribonucleotides (those that have 2-deoxyribose as the pentose) is to serve as building blocks for DNA. Although ribonucleotides similarly serve as the units for RNA synthesis, they also have a multitude of other functions in cell metabolism. In some synthetic nucleosides with therapeutic properties, other pentose components such as arabinose are present. (See fig. 12.2 for the structure of arabinose.)... [Pg.535]

Hydroxyurea interferes with the synthesis of both pyrimidine and purine nucleotides (see table 23.3). It interferes with the synthesis of deoxyribonucleotides by inhibiting ribonucleotide reductase of mammalian cells, an enzyme that is crucial and probably rate-limiting in the biosynthesis of DNA. It probably acts by disrupting the iron-tyrosyl radical structure at the active site of the reductase. Hydroxyurea is in clinical use as an anticancer agent. [Pg.551]

The nucleotides of DNA are called deoxyribonucleotides, since they contain the sugar deoxyribose, whereas, those of RNA are called nbonucleotides since they contain nbose instead. Each nucleotide contains both a specific and a nonspecific region. The phosphate and sugar groups are the nonspecific portion of the nucleotide, while the purine and pyrimidine bases make up the specific portion. [Pg.177]

Chemotherapeutic agents, useful in me treatment of neoplastic diseases, exert their therapeutic effects by modifying me synthesis or functions of nucleic acids (see Chapter 51 and Chapter 58). For example, 6-mercaptopurine inhibits purine-ring biosynthesis, cytarabine inhibits DNA polymerase, alkylating agents crosslink DNA, and hydroxyurea inhibits the conversion of ribonucleotides into deoxyribonucleotides. However, other pharmacologic agents such as chlorpromazine, a... [Pg.28]

As much of the terminology used in molecular biology may be unfamiliar to some readers, it is appropriate to define some of the vocabulary and this is given in an appendix to this chapter. There are two types of nucleic acids, the ribonucleic acids (RNA) and the deoxyribonucleic acids (DNA). Genetic information is carried in the linear sequence of nucleotides in DNA. Each molecule of DNA contains two complementary strands of deoxyribonucleotides which contain the purine bases, adenine and guanine and the pyrimidines, cytosine and thymine. RNA is single-stranded, being composed of a linear sequence of ribonucleotides the bases are the same as in DNA with the exception that thymine is replaced by the closely related base uracil. DNA replication occurs by the polymerisation of a new complementary strand on to each of the old strands. [Pg.140]

Understand the purine and pyrmidine de novo biosynthetic pathways, with special attention to enzymes controlling pathway rates and the properties of such enzymes the positive and negative effectors steps inhibited by the various antitumor agents and their mechanisms final products of the de novo pathways and how the various nucleotides are generated from them and the biosynthesis of deoxyribonucleotides and the attendant mechanisms. [Pg.263]

Inhibition of nudeobase synthesis (2). Tet-rahydrofolic acid (THF) is required for the synthesis of both purine bases and thymidine. Formation of THF from folic acid involves dihydrofolate reductase (p. 274). The folate analogues aminopterin and methotrexate (amethopterin) inhibit enzyme activity. Cellular stores of THF are depleted. The effect of these antimetabolites can be reversed by administration of folinic acid (5-formyl-THF, leucovorin, citrovorum factor). Hydroxyurea (hydroxycarbamide) inhibits ribonucleotide reductase that normally converts ribonucleotides into deoxyribonucleotides subsequently used as DNA building blocks. [Pg.300]

Figure 1.4 Diagrammatic representations of (a) a purine base, (b) a pyrimidine base, (c) a ribonucleotide, adenosine monophosphate (AMP) and (d) a deoxyribonucleotide, deoxyuridine monophosphate (dllMP). Figure 1.4 Diagrammatic representations of (a) a purine base, (b) a pyrimidine base, (c) a ribonucleotide, adenosine monophosphate (AMP) and (d) a deoxyribonucleotide, deoxyuridine monophosphate (dllMP).
Deoxyribonucleotide (Section 27.14B) ADNAbuilding block having a deoxyribose and either a purine or pyrimidine base joined together by an (V-glycosidic linkage, and a phosphate bonded to a hydroxy group of the sugar nucleus. [Pg.1199]

Cobalamin enzymes, which are present in most organisms, catalyze three types of reactions (1) intramolecular rearrangements (2) methylations, as in the synthesis of methionine (Section 24.2.7) and (3) reduction of ribonucleotides to deoxyribonucleotides (Section 25.3). In mammals, the conversion of 1-methylmalonyl CoA into succinyl CoA and the formation of methionine by methylation of homocysteine are the only reactions that are known to require coenzyme Bj2. The latter reaction is especially important because methionine is required for the generation of coenzymes that participate in the synthesis of purines and thymine, which are needed for nucleic acid synthesis. [Pg.911]

Narrower specificities have been obtained with antibodies to some unusual helical structures. Poly(dG)-poly(dC) induces antibodies specific for the immunogen and unreactive with other deoxyribonucleotide polymers, such as poly(dAT) or native DNA. Double-helical polyribonucleotides with modified furanoses, such as poly(A)-poly(2 -0-methylU), induce antibodies that react with a number of polymers bearing 2 -furanose substitutions (such as methyl or ethyl groups on either the purine or pyrimidine-containing strand). Poly(G)-poly(C) induced antibodies of narrow specificity in our studies, but Lacour and co-workers obtained anti-poly(G)-poly(C) that cross-reacted with several forms of viral RNA. ... [Pg.80]

There are four different heterocyclic amine bases in deoxyribonucleotides. Two are substituted purines (adenine and guanine), and two are. substituted pyrimidines (cytosine and thymine). Adenine, guanine, and cytosine also occur in RNA, but thymine is replaced in RNA by a different pyrimidine base called uracil. [Pg.1161]


See other pages where Purine deoxyribonucleotides is mentioned: [Pg.306]    [Pg.624]    [Pg.395]    [Pg.70]    [Pg.475]    [Pg.455]    [Pg.306]    [Pg.624]    [Pg.395]    [Pg.70]    [Pg.475]    [Pg.455]    [Pg.303]    [Pg.113]    [Pg.448]    [Pg.259]    [Pg.1175]    [Pg.83]    [Pg.274]    [Pg.113]    [Pg.411]    [Pg.57]    [Pg.221]    [Pg.279]    [Pg.50]    [Pg.141]    [Pg.168]    [Pg.71]    [Pg.394]    [Pg.68]   


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