Wikia

Psychology Wiki

Nucleotides

Talk0
34,135pages on
this wiki
Revision as of 17:18, January 2, 2010 by Dr Joe Kiff (Talk | contribs)

Assessment | Biopsychology | Comparative | Cognitive | Developmental | Language | Individual differences | Personality | Philosophy | Social |
Methods | Statistics | Clinical | Educational | Industrial | Professional items | World psychology |

Biological: Behavioural genetics · Evolutionary psychology · Neuroanatomy · Neurochemistry · Neuroendocrinology · Neuroscience · Psychoneuroimmunology · Physiological Psychology · Psychopharmacology (Index, Outline)


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.

Nucleotides

The structure elements of the most common nucleotides

Nomenclature

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

Nucleotides

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

Deoxynucleotides

DAMP chemical structure
Deoxyadenosine monophosphate
dAMP
DADP chemical structure
Deoxyadenosine diphosphate
dADP
DATP chemical structure
Deoxyadenosine triphosphate
dATP
DGMP chemical structure
Deoxyguanosine monophosphate
dGMP
DGDP chemical structure
Deoxyguanosine diphosphate
dGDP
DGTP chemical structure
Deoxyguanosine triphosphate
dGTP
DTMP chemical structure
Deoxythymidine monophosphate
dTMP
DTDP chemical structure
Deoxythymidine diphosphate
dTDP
DTTP chemical structure
Deoxythymidine triphosphate
dTTP
DUMP chemical structure
Deoxyuridine monophosphate
dUMP
DUDP chemical structure
Deoxyuridine diphosphate
dUDP
DUTP chemical structure
Deoxyuridine triphosphate
dUTP
DCMP chemical structure
Deoxycytidine monophosphate
dCMP
DCDP chemical structure
Deoxycytidine diphosphate
dCDP
DCTP chemical structure
Deoxycytidine triphosphate
dCTP

Synthesis

Natural

Purine ribonucleotides

Nucleotides syn1

The synthesis of IMP.
The color scheme is as follows: enzymes, coenzymes, substrate names, metal ions, inorganic molecules

Nucleotides syn3

The biosynthetic origins of purine ring atoms

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 (PPi) 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 PPi, is the pathway's flux generating step and is therefore regulated too.

Reaction 3.

</td></tr>

Pyrimidine ribonucleotides

Nucleotides syn2

The synthesis of UMP.
The color scheme is as follows: enzymes, coenzymes, substrate names, inorganic molecules

</td></tr></table>

See also

External links

This page uses Creative Commons Licensed content from Wikipedia (view authors).

Around Wikia's network

Random Wiki