Hypoxanthine is a naturally occurring
purine derivative. It is occasionally found as a constituent of
nucleic acid
Nucleic acids are biopolymers, macromolecules, essential to all known forms of life. They are composed of nucleotides, which are the monomers made of three components: a 5-carbon sugar, a phosphate group and a nitrogenous base. The two main cl ...
s, where it is present in the
anticodon of
tRNA in the form of its nucleoside
inosine. It has a
tautomer known as 6-hydroxypurine. Hypoxanthine is a necessary additive in certain cells, bacteria, and parasite cultures as a substrate and nitrogen source. For example, it is commonly a required
reagent
In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...
in
malaria parasite cultures, since ''
Plasmodium falciparum
''Plasmodium falciparum'' is a Unicellular organism, unicellular protozoan parasite of humans, and the deadliest species of ''Plasmodium'' that causes malaria in humans. The parasite is transmitted through the bite of a female ''Anopheles'' mosqu ...
'' requires a source of hypoxanthine for nucleic acid synthesis and energy metabolism.
In August 2011, a report, based on
NASA studies with
meteorite
A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or Natural satellite, moon. When the ...
s found on Earth, was published suggesting hypoxanthine and related
organic molecules
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The s ...
, including the
DNA and
RNA
Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...
components
adenine and
guanine, may have been formed extraterrestrially in outer space.
The ''
Pheretima aspergillum'' worm, used in Chinese medicine preparations, contains hypoxanthine.
Reactions
It is one of the products of the action of
xanthine oxidase on
xanthine. However, more frequently in
purine degradation, xanthine is formed from oxidation of hypoxanthine by
xanthine oxidoreductase.
Hypoxanthine-guanine phosphoribosyltransferase
Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) is an enzyme encoded in humans by the ''HPRT1'' gene.
HGPRT is a transferase that catalyzes conversion of hypoxanthine to inosine monophosphate and guanine to guanosine monophosphate. This r ...
converts hypoxanthine into
IMP in
nucleotide salvage.
Hypoxanthine is also a spontaneous
deamination product of
adenine. Because of its resemblance to
guanine, the spontaneous deamination of adenine can lead to an error in
DNA transcription/replication, as it base pairs with
cytosine. Hypoxanthine is removed from DNA by base excision repair, initiated by N-methylpurine glycosylase (MPG), also known as alkyl adenine glycosylase (Aag).
Additional images
Image:Adenin.svg, Adenine
Image:Guanin.svg, Guanine
Image:Xanthin.svg, Xanthine
References
External links
*
{{Purinergics
Purines
Nucleobases