Phosphoribosyl-''N''-formylglycineamide (or FormylGlycinAmideRibotide, FGAR) 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 puri ...
nucleotides
Nucleotides are Organic compound, organic molecules composed of a nitrogenous base, a pentose sugar and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both o ...
via
inosine
Inosine is a nucleoside that is formed when hypoxanthine is attached to a ribose ring (also known as a ribofuranose) via a β-N9-glycosidic bond. It was discovered in 1965 in analysis of RNA transferase.
Inosine is commonly found in tRNAs and is ...
-5-monophosphate, and hence is a building block for
DNA
Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...
and
RNA
Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself (non-coding RNA) or by forming a template for the production of proteins (messenger RNA). RNA and deoxyrib ...
.
The vitamins
thiamine
Thiamine, also known as thiamin and vitamin B1, is a vitamin – an Nutrient#Micronutrients, essential micronutrient for humans and animals. It is found in food and commercially synthesized to be a dietary supplement or medication. Phosp ...
and
cobalamin
Vitamin B12, also known as cobalamin, is a water-soluble vitamin involved in metabolism. One of eight B vitamins, it serves as a vital cofactor (biochemistry), cofactor in DNA synthesis and both fatty acid metabolism, fatty acid and amino a ...
also contain fragments derived from FGAR.
FGAR is formed when the enzyme
phosphoribosylglycinamide formyltransferase
Phosphoribosylglycinamide formyltransferase (), also known as glycinamide ribonucleotide transformylase (GAR Tfase), is an enzyme with systematic name ''10-formyltetrahydrofolate:5'-phosphoribosylglycinamide N-formyltransferase''. This enzyme cat ...
adds a
formyl group from
10-formyltetrahydrofolate to
glycineamide ribonucleotide
Glycinamide ribonucleotide (or GAR) is a biochemical intermediate in the formation of purine nucleotides via inosine-5-monophosphate, and hence is a building block for DNA and RNA. The vitamins thiamine and cobalamin also contain fragments derived ...
(GAR) in reaction :
:GAR + 10-formyltetrahydrofolate → FGAR + tetrahydrofolate
The biosynthesis pathway next converts FGAR to an
amidine
Amidines are organic compounds with the functional group RC(NR)NR2, where the R groups can be the same or different. They are the imine derivatives of amides (RC(O)NR2). The simplest amidine is formamidine, HC(=NH)NH2.
Examples of amidines includ ...
by the action of
phosphoribosylformylglycinamidine synthase (), transferring an amino group from glutamine and giving
5'-phosphoribosylformylglycinamidine (FGAM) in a reaction that also requires ATP:
[
:FGAR + ATP + glutamine + H2O → FGAM + ADP + glutamate + Pi]
See also
* 5-Aminoimidazole ribotide
* Purine metabolism
Purine metabolism refers to the metabolic pathways to synthesize and break down purines that are present in many organisms.
Biosynthesis
Purines are biologically synthesized as nucleotides and in particular as ribotides, i.e. bases attached to r ...
References
{{Nucleotide metabolism intermediates
Nucleotides