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A nucleotide is a chemical compound that consists of 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 pentose - deoxyribose or ribose.

Nucleotides are the structural units of RNA, DNA, and several cofactors - CoA, FAD, FMN, NAD, and NADP. In the cell they play important roles in energy production, metabolism, and signaling.

Nomenclature Edit

Nucleotide codes
Code	Equivalence	Complement
A	A	T or U
C	C	G
G	G	C
T or U	T	A
M	A or C	K
R	A or G	Y
W	A or T	W
S	C or G	S
Y	C or T	R
K	G or T	M
V	A or C or G	B
H	A or C or T	D
D	A or G or T	H
B	C or G or T	V
X or N	A or C or G or T	X

Nucleotide names are abbreviated into standard four-letter codes. The first letter is lower case and indicates whether the nucleotide in question is a ribonucleotide (r) or deoxyribonucleotide (d). The second letter indicates the nucleoside corresponding to the nucleobase:

G: Guanine

A: Adenine

T: Thymine

C: Cytosine

U: Uracil not usually present in DNA, but takes the place of Thymine in RNA

The third and fourth letters indicate the length of the attached phosphate chain (Mono-, Di-, Tri-) and the presence of a phosphate (P).

For example, deoxy-cytidine-triphosphate is abbreviated as dCTP.

Chemical structures Edit

Nucleotides Edit

Adenosine monophosphate AMP	Adenosine diphosphate ADP	Adenosine triphosphate ATP
Guanosine monophosphate GMP	Guanosine diphosphate GDP	Guanosine triphosphate GTP
Thymidine monophosphate TMP	Thymidine diphosphate TDP	Thymidine triphosphate TTP
Uridine monophosphate UMP	Uridine diphosphate UDP	Uridine triphosphate UTP
Cytidine monophosphate CMP	Cytidine diphosphate CDP	Cytidine triphosphate CTP

Deoxynucleotides Edit

Deoxyadenosine monophosphate dAMP	Deoxyadenosine diphosphate dADP	Deoxyadenosine triphosphate dATP
Deoxyguanosine monophosphate dGMP	Deoxyguanosine diphosphate dGDP	Deoxyguanosine triphosphate dGTP
Deoxythymidine monophosphate dTMP	Deoxythymidine diphosphate dTDP	Deoxythymidine triphosphate dTTP
Deoxyuridine monophosphate dUMP	Deoxyuridine diphosphate dUDP	Deoxyuridine triphosphate dUTP
Deoxycytidine monophosphate dCMP	Deoxycytidine diphosphate dCDP	Deoxycytidine triphosphate dCTP

SynthesisEdit

NaturalEdit

Purine ribonucleotidesEdit

Nucleotides syn3 — **The biosynthetic origins of purine ring atoms**
Added by PhloxBot

By using a variety of isotopically labeled compounds it was demonstrated that N1 of purines 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; and 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) and 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 establishsing 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.

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Pyrimidine ribonucleotidesEdit

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External links Edit

Nucleic acids edit
Nucleobases: Adenine - Thymine - Uracil - Guanine - Cytosine - Purine - Pyrimidine
Nucleosides: Adenosine - Uridine - Guanosine - Cytidine - Deoxyadenosine - Thymidine - Deoxyguanosine - Deoxycytidine
Nucleotides: AMP - UMP - GMP - CMP - ADP - UDP - GDP - CDP - ATP - UTP - GTP - CTP - cAMP - cGMP
Deoxynucleotides: dAMP - dTMP - dUMP - dGMP - dCMP - dADP - dTDP - dUDP - dGDP - dCDP - dATP - dTTP - dUTP - dGTP - dCTP
Nucleic acids: DNA - RNA - LNA - PNA - mRNA - ncRNA - miRNA - rRNA - siRNA - tRNA - cDNA - snRNA - snoRNA - mtDNA - Oligonucleotide

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