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A 'nucleotide' is a chemical compound that consists of 3 portions: a heterocyclic base, a sugar, and one or more phosphate groups. In the most common nucleotides the base is a derivative of purine or pyrimidine, and the sugar is the pentose (five-carbon sugar) deoxyribose or ribose. Nucleotides are the monomers of nucleic acids, with three or more bonding together in order to form a nucleic acid.
Nucleotides are the structural units of RNA, DNA, and several cofactors - CoA, flavin adenine dinucleotide, flavin mononucleotide, adenosine triphosphate and nicotinamide adenine dinucleotide phosphate. In the cell they have important roles in metabolism and signaling.

Contents

Nucleotides

Deoxynucleotides

Synthesis

Natural

Purine ribonucleotides

Pyrimidine ribonucleotides

See also

External links

Nucleotides

Chemical structure of adenosine monophosphate Adenosine monophosphate AMP	Chemical structure of adenosine diphosphate Adenosine diphosphate ADP	Chemical structure of adenosine triphosphate Adenosine triphosphate ATP
Chemical structure of guanosine monophosphate Guanosine monophosphate GMP	Chemical structure of guanosine diphosphate Guanosine diphosphate GDP	Chemical structure of guanosine triphosphate Guanosine triphosphate GTP
Chemical structure of thymidine monophosphate Thymidine monophosphate TMP	Chemical structure of thymidine diphosphate Thymidine diphosphate TDP	Chemical structure of thymidine triphosphate Thymidine triphosphate TTP
Chemical structure of uridine monophosphate Uridine monophosphate UMP	Chemical structure of uridine diphosphate Uridine diphosphate UDP	Chemical structure of uridine triphosphate Uridine triphosphate UTP
Chemical structure of cytidine monophosphate Cytidine monophosphate CMP	Chemical structure of cytidine diphosphate Cytidine diphosphate CDP	Chemical structure of cytidine triphosphate Cytidine triphosphate CTP

Deoxynucleotides

Chemical structure of deoxyadenosine monophosphate Deoxyadenosine monophosphate dAMP	Chemical structure of deoxyadenosine diphosphate Deoxyadenosine diphosphate dADP	Chemical structure of deoxyadenosine triphosphate Deoxyadenosine triphosphate dATP
Chemical structure of deoxyguanosine monophosphate Deoxyguanosine monophosphate dGMP	Chemical structure of deoxyguanosine diphosphate Deoxyguanosine diphosphate dGDP	Chemical structure of deoxyguanosine triphosphate Deoxyguanosine triphosphate dGTP
Chemical structure of deoxythymidine monophosphate Deoxythymidine monophosphate dTMP	Chemical structure of deoxythymidine diphosphate Deoxythymidine diphosphate dTDP	Chemical structure of deoxythymidine triphosphate Deoxythymidine triphosphate dTTP
Chemical structure of deoxyuridine monophosphate Deoxyuridine monophosphate dUMP	Chemical structure of deoxyuridine diphosphate Deoxyuridine diphosphate dUDP	Chemical structure of deoxyuridine triphosphate Deoxyuridine triphosphate dUTP
Chemical structure of deoxycytidine monophosphate Deoxycytidine monophosphate dCMP	Chemical structure of deoxycytidine diphosphate Deoxycytidine diphosphate dCDP	Chemical structure of deoxycytidine triphosphate Deoxycytidine triphosphate dCTP

Synthesis

''Salvage synthesis'' refers to the reuse of parts of nucleotides in resynthesizing new nucleotides. Salvage synthesis requires both breakdown and synthesis reactions in order to exchange the useful parts.

Natural

Purine ribonucleotides

By using a variety of isotopically labeled compounds it was demonstrated that the sources of the atoms in purines are as follows:

Nucleotides_syn3.png

'The biosynthetic origins of purine ring atoms' N1 arises from the amine group of Asp C2 and C8 originate from formate N3 and N9 are contributed by the amide group of Gln C4, C5 and N7 are derived from Gly C6 comes from HCO3- (CO2)

The de novo synthesis of purine nucleotides by which these precursors are incorporated into the purine ring, proceeds by a 10 step pathway to the branch point intermediate IMP, the nucleotide of the base hypoxanthine. AMP and GMP are subsequently synthesized from this intermediate via separate, two step each, pathways. Thus purine moieties are initially formed as part of the ribonucleotides rather than as free bases.
Six enzymes take part in IMP synthesis. Three of them are multifunctional:

★ GART (reactions 2, 3, and 5)

★ PAICS (reactions 6, and 7)

★ ATIC (reactions 9, and 10)
'Reaction 1'. The pathway starts with the formation of PRPP. PRPS1 is the enzyme that activates R5P, which is primarily formed by the pentose phosphate pathway, to PRPP by reacting it with ATP. The reaction is unusual in that a pyrophosphoryl group is directly transferred from ATP to C1 of R5P and that the product has the 'α' configuration about C1. This reaction is also shared with the pathways for the synthesis of the pyrimidine nucleotides, Trp, and His. As a result of being on (a) such (a) major metabolic crossroad and the use of energy, this reaction is highly regulated.
'Reaction 2'. In the first reaction unique to purine nucleotide biosynthesis, PPAT catalyzes the displacement of PRPP's pyrophosphate group (PP_i) by Gln's amide nitrogen. The reaction occurs with the inversion of configuration about ribose C1, thereby forming 'β'-5-phosphorybosylamine (5-PRA) and establishing the anomeric form of the future nucleotide. This reaction which is driven to completion by the subsequent hydrolysis of the released PP_i, is the pathway's flux generating step and is therefore regulated too.
'Reaction 3'.

Pyrimidine ribonucleotides

See also

★ Gene

★ Genetics

★ Chromosome

External links

★ Abbreviations and Symbols for Nucleic Acids, Polynucleotides and their Constituents (IUPAC)

★ Provisional Recommendations 2004 (IUPAC)

★ Chemistry explanation of nucleotide structure