Phosphoribosyl pyrophosphate (PRPP) is a
pentose phosphate. It is a biochemical intermediate in the formation of
purine
Purine is a heterocyclic aromatic organic compound that consists of two rings ( pyrimidine and imidazole) fused together. It is water-soluble. Purine also gives its name to the wider class of molecules, purines, which include substituted purines ...
nucleotides
Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecules with ...
via
inosine-5-monophosphate, as well as in
pyrimidine nucleotide formation. Hence it is a building block for
DNA and
RNA.
The vitamins
thiamine
Thiamine, also known as thiamin and vitamin B1, is a vitamin, an essential micronutrient, that cannot be made in the body. It is found in food and commercially synthesized to be a dietary supplement or medication. Phosphorylated forms of thi ...
and
cobalamin
Vitamin B12, also known as cobalamin, is a water-soluble vitamin involved in metabolism. It is one of eight B vitamins. It is required by animals, which use it as a cofactor in DNA synthesis, in both fatty acid and amino acid metabolism. ...
,
and the amino acid
tryptophan
Tryptophan (symbol Trp or W)
is an α-amino acid that is used in the biosynthesis of proteins. Tryptophan contains an α-amino group, an α-carboxylic acid group, and a side chain indole, making it a polar molecule with a non-polar aromatic ...
also contain fragments derived from PRPP.
It is formed from
ribose 5-phosphate
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, r ...
(R5P) by the enzyme
ribose-phosphate diphosphokinase
Ribose-phosphate diphosphokinase (or phosphoribosyl pyrophosphate synthetase or ribose-phosphate pyrophosphokinase) is an enzyme that converts ribose 5-phosphate into phosphoribosyl pyrophosphate (PRPP). It is classified under .
The enzyme is i ...
:
:
It plays a role in transferring phospho-ribose groups in several reactions, some of which are
salvage pathway A salvage pathway is a pathway in which a biological product is produced from intermediates in the degradative pathway of its own or a similar substance. The term often refers to nucleotide salvage in particular, in which nucleotides (purine and py ...
s:
In ''
de novo'' generation of purines, the enzyme
amidophosphoribosyltransferase acts upon PRPP to create
phosphoribosylamine.
[ The ]histidine
Histidine (symbol His or H) is an essential amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated –NH3+ form under biological conditions), a carboxylic acid group (which is in the d ...
biosynthesis pathway involves the reaction between PRPP and ATP, which activates the latter to ring cleavage. Carbon atoms from ribose in PRPP form the linear chain and part of the imidazole ring in histidine. The same is true for the biosynthesis of tryptophan, with the first step being N-alkylation of anthranilic acid
Anthranilic acid is an aromatic acid with the formula C6H4(NH2)(CO2H) and has a sweetish taste. The molecule consists of a benzene ring, ''ortho''-substituted with a carboxylic acid and an amine. As a result of containing both acidic and basic ...
catalysed by the enzyme anthranilate phosphoribosyltransferase
In enzymology, an anthranilate phosphoribosyltransferase () is an enzyme that catalyzes the chemical reaction
:anthranilate + phosphoribosyl pyrophosphate \rightleftharpoons N-(5-phosphoribosyl)-anthranilate + diphosphate
The two substrates o ...
.
Increased PRPP
Increased levels of PRPP are characterized by the overproduction and accumulation of uric acid
Uric acid is a heterocyclic compound of carbon, nitrogen, oxygen, and hydrogen with the formula C5H4N4O3. It forms ions and salts known as urates and acid urates, such as ammonium acid urate. Uric acid is a product of the metabolic breakdown ...
leading to hyperuricemia
Hyperuricaemia or hyperuricemia is an abnormally high level of uric acid in the blood. In the pH conditions of body fluid, uric acid exists largely as urate, the ion form. Serum uric acid concentrations greater than 6 mg/dL for females, 7&nbs ...
and hyperuricosuria
Hyperuricosuria is a medical term referring to the presence of excessive amounts of uric acid in the urine. For men this is at a rate greater than 800 mg/day, and for women, 750 mg/day. Notable direct causes of hyperuricosuria are dissol ...
. It is one of the causes of gout
Gout ( ) is a form of inflammatory arthritis characterized by recurrent attacks of a red, tender, hot and swollen joint, caused by deposition of monosodium urate monohydrate crystals. Pain typically comes on rapidly, reaching maximal intens ...
.
Increased levels of PRPP are present in Lesch–Nyhan Syndrome
Lesch–Nyhan syndrome (LNS) is a rare inherited disorder caused by a deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT). This deficiency occurs due to mutations in the ''HPRT1'' gene located on the X chromosome. LNS ...
. Decreased levels of hypoxanthine guanine phosphoribosyl transferase
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 ...
(HGPRT) causes this accumulation, as PRPP is a substrate used by HGPRT during purine
Purine is a heterocyclic aromatic organic compound that consists of two rings ( pyrimidine and imidazole) fused together. It is water-soluble. Purine also gives its name to the wider class of molecules, purines, which include substituted purines ...
salvage.
See also
* 5-Aminoimidazole ribotide
* Purine biosynthesis
* Pyrimidine biosynthesis
References
{{DEFAULTSORT:Phosphoribosyl Pyrophosphate
Organophosphates
Monosaccharides