Guanine

  • 2 -amino-1 ,9- dihydropurin -6-one (IUPAC)
  • 2-amino -6-oxo -purin

White to yellowish white solid

Fixed

> 365 ° C ( decomposition)

  • Insoluble in water
  • Soluble in dilute acids and alkalis
  • Sparingly soluble in ethanol and diethyl ether

Attention

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Guanine (G, Gua ) is one of four major nucleobases in DNA and RNA together with adenine, cytosine and thymine ( uracil in RNA). Is a heterocyclic organic compound with a purine basic structure and two substituents ( an amino group in the 2-position and a keto group at position 6). The nucleoside of guanine in DNA is the deoxyguanosine and guanosine in RNA. In the Watson -Crick base pairing, it forms three hydrogen bonds with cytosine.

Biosynthesis and metabolism

The organism of most living organisms is to synthesize able guanine itself; because this pathway is very energy consuming, the body via the salvage pathway, the purine derivative guanine also reuse, cut from degraded nucleic acid molecules and bind again to ribose as needed.

The degradation of guanine to xanthine takes place and further to uric acid.

In reptiles and birds represents guanine next to uric acid excretion is an important form of nitrogen (mainly from the protein and Nukleotidabbau ) Represents the elimination product is paste-like and contains little water, so that its mass must not be carried, which supports the ability to fly. This is more energy efficient than to use the chemical energy contained in the guanine. For the same reason bats guanine eliminated. On the distinctive in guanine ( and uric acid) forms after weathering the guano, especially on calcareous soils.

Representation

A display is provided via the Traube synthesis by heating of 2,4,5- triamine -1 ,6-dihydro -6- oxopyrimidine ( as sulphate) with formic acid for several hours.

Properties

Guanine is a white to yellowish white solid which melts above 365 ° C with decomposition. It is insoluble in water, soluble in dilute acids and alkalis, sparingly soluble in ethanol and diethyl ether.

Biological Significance

Guanine may be part of the DNA, RNA, or various nucleosides and nucleotides.

Nucleosides

About the N9 atom of the guanine five-membered ring can be attached N- glycosidically linked to the C1 atom of the ribose; this is called a nucleoside, the guanosine. When binding to deoxyribose creates the nucleoside deoxyguanosine.

Nucleotides

About the phosphorylation of guanosine on the C5 atom of the ribose leads to the important nucleotides guanosine monophosphate ( GMP), guanosine diphosphate (GDP) and guanosine triphosphate (GTP ), and analogously for the deoxyguanosine to deoxyguanosine monophosphate ( dGMP ), Desoxyguanosindiphosphat ( DGDP ) and deoxyguanosine triphosphate ( dGTP ).

Part of the DNA and RNA

In the DNA double helix form of the oxo group of guanine, the N1 atom, and the amino group of three hydrogen bonds with the corresponding cytosine base of the complementary strand.

Pathophysiology

In disorders of the salvage pathway, especially in a defect in the enzyme hypoxanthine guanine phosphoribosyl transferase ( HGPRT ), it comes to the symptoms of the Lesch -Nyhan syndrome.

With a too high amount of metabolized guanine, the resultant, non-physiologically high amount of uric acid ( hyperuricemia ) in the kidney, the urinary tract or in bradytrophic tissues (especially joint capsules ) crystallize and lead to urinary stones or gout.

Related compounds

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