Ribose 5-phosphate
Names | |
---|---|
IUPAC name
5-O-Phosphono-D-ribose
| |
Other names
Ribose 5-phosphate
| |
Identifiers | |
3D model (
JSmol ) |
|
ChEBI | |
ChemSpider | |
ECHA InfoCard
|
100.022.101 |
MeSH | ribose-5-phosphate |
PubChem CID
|
|
UNII | |
CompTox Dashboard (EPA)
|
|
| |
| |
Properties | |
C5H11O8P | |
Molar mass | 230.110 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|
Ribose 5-phosphate (R5P) is both a product and an intermediate of the pentose phosphate pathway. The last step of the oxidative reactions in the pentose phosphate pathway is the production of ribulose 5-phosphate. Depending on the body's state, ribulose 5-phosphate can reversibly isomerize to ribose 5-phosphate. Ribulose 5-phosphate can alternatively undergo a series of isomerizations as well as transaldolations and transketolations that result in the production of other pentose phosphates as well as fructose 6-phosphate and glyceraldehyde 3-phosphate (both intermediates in glycolysis).
The enzyme ribose-phosphate diphosphokinase converts ribose-5-phosphate into phosphoribosyl pyrophosphate.
Structure
R5P consists of a five-carbon sugar, ribose, and a phosphate group at the five-position carbon. It can exist in open chain form or in furanose form. The furanose form is most commonly referred to as ribose 5-phosphoric acid.[1]
Biosynthesis
The formation of R5P is highly dependent on the cell growth and the need for
Pentose phosphate pathway
R5P is produced in the
When demand for NADPH and R5P is balanced, G6P forms one Ru5P molecule through the PPP, generating two NADPH molecules and one R5P molecule.[2]
Glycolysis
When more R5P is needed than NADPH, R5P can be formed through
Function
R5P and its derivatives serve as precursors to many biomolecules, including
Nucleotide biosynthesis
Nucleotides serve as the building blocks for nucleic acids, DNA and RNA.[6] They are composed of a nitrogenous base, a pentose sugar, and at least one phosphate group. Nucleotides contain either a purine or a pyrimidine nitrogenous base. All intermediates in purine biosynthesis are constructed on a R5P "scaffold".[7] R5P also serves as an important precursor to pyrimidine ribonucleotide synthesis.
During nucleotide biosynthesis, R5P undergoes activation by
PRPP also plays an important role in pyrimidine ribonucleotide synthesis. During the fifth step of pyrimidine nucleotide synthesis, PRPP covalently links to
Histidine biosynthesis
Histidine is an essential amino acid that is not synthesized de novo in humans. Like nucleotides, biosynthesis of histidine is initiated by the conversion of R5P to PRPP. The step of histidine biosynthesis is the condensation of ATP and PRPP by ATP-phosphoribosyl transferase, the rate determining enzyme. Histidine biosynthesis is carefully regulated by feedback inhibition/[11]
Other functions
R5P can be converted to adenosine diphosphate ribose, which binds and activates the TRPM2 ion channel. The reaction is catalyzed by ribose-5-phosphate adenylyltransferase[12]
Disease relevance
Diseases have been linked to R5P imbalances in cells. Cancers and tumors show upregulated production of R5P correlated to increased RNA and DNA synthesis.[2] Ribose 5-phosphate isomerase deficiency, the rarest disease in the world,[13][14] is also linked to an imbalance of R5P. Although the molecular pathology of the disease is poorly understood, hypotheses included decreased RNA synthesis. Another disease linked to R5P is gout.[15] Higher levels of G6P lead to a buildup of glycolytic intermediates, that are diverted to R5P production. R5P converts to PRPP, which forces an overproduction of purines, leading to uric acid build up.[8]
Accumulation of PRPP is found in
Superactivity in PRPS1, the enzyme that catalyzes the R5P to PRPP, has also been linked to gout, as well as neurodevelopmental impairment and sensorineural deafness.[17]
References
- ^ Levene PA, Stiller ET (February 1934). "The Synthesis of Ribose-5-Phosphoric Acid". Journal of Biological Chemistry. 104 (2): 299–306.
- ^ ISBN 978-1-4292-7635-1.
- PMID 12753973.
- PMID 12517338.
- ISBN 9780080552323.
- ISBN 978-0-9678550-9-7.
- ISBN 978-0-12-391909-0.
- ^ ISBN 9780323074469.
- ISBN 978-0-12-391909-0.
- )
- PMID 22303266.
- PMID 4287446.
- PMID 20499043.
- PMID 14988808.
- ISBN 978-1-4377-2864-4.
- ISBN 978-0-12-449851-8.
- ISBN 978-0-7506-9852-8.