Guanosine monophosphate (GMP), also known as 5′-guanidylic acid or guanylic acid (conjugate base guanylate), is a nucleotide that is used as a monomer in RNA. It is an ester of phosphoric acid with the nucleoside guanosine. GMP consists of the phosphate group, the pentose sugar ribose, and the nucleobase guanine; hence it is a ribonucleotide monophosphate. Guanosine monophosphate is commercially produced by microbial fermentation.^[1]

Quick Facts Names, Identifiers ...

Guanosine monophosphate

Names
IUPAC name 5′-Guanylic acid
Systematic IUPAC name [(2R,3S,4R,5R)-5-(2-Amino-6-oxo-1,6-dihydro-9H-purin-9-yl)-3,4-dihydroxyoxolan-2-yl]methyl dihydrogen phosphate
Other names 5′-Guanidylic acid E number E626
Identifiers
CAS Number	85-32-5 Y
3D model (JSmol)	Interactive image
Abbreviations	GMP
ChEMBL	ChEMBL604603 N
ChemSpider	6545 N
ECHA InfoCard	100.001.453
E number	E626 (flavour enhancer)
IUPHAR/BPS	5123
MeSH	Guanosine+monophosphate
PubChem CID	135398631
UNII	16597955EP Y
CompTox Dashboard (EPA)	DTXSID9044295
SMILES C1=NC2=C(N1[C@H]3[C@@H]([C@@H]([C@H](O3)COP(=O)(O)O)O)O)NC(=NC2=O)N
Properties
Chemical formula	C10H14N5O8P
Molar mass	363.223 g·mol−1
Acidity (pKa)	0.7, 2.4, 6.1, 9.4
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

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As an acyl substituent, it takes the form of the prefix guanylyl-.

GMP synthesis starts with D-ribose 5′-phosphate, a product of the pentose phosphate pathway. The synthesis proceeds by the gradual formation of the purine ring on carbon-1 of ribose, with CO₂, glutamine, glycine, aspartate and one-carbon derivatives of tetrahydrofolate donating various elements towards the building of the ring.^[2]

As inhibitor of guanosine monophosphate synthesis in experimental models, the glutamine analogue DON can be used.^[3]

GMP can also exist as a cyclic structure known as cyclic GMP. Within certain cells the enzyme guanylyl cyclase makes cGMP from GTP.

cGMP plays an important role in mediating hormonal signaling.^[2]

GMP was originally identified as the umami substance in dried shiitake mushroom. The drying process significantly increases GMP content with the breakdown of RNA. It can be found in a number of other mushrooms.^[4]

Industrial production is based on fermentation: a bacterium converts sugars into AICA ribonucleotide, which is then converted chemically to GMP.^[5] Tapioca starch is a possible sugar source.^[6]

Guanosine monophosphate is known as E number reference E626.^[7] In the form of its salts, such as disodium guanylate (E627), dipotassium guanylate (E628) and calcium guanylate (E629), are food additives used as flavor enhancers to provide the umami taste.^[7] It is often used in synergy with disodium inosinate; the combination is known as disodium 5′-ribonucleotides. Disodium guanylate is often found in instant noodles, potato chips and snacks, savoury rice, tinned vegetables, cured meats, and packet soup.

As it is a fairly expensive additive, it is usually not used independently of glutamic acid or monosodium glutamate (MSG), which also contribute umami. If inosinate and guanylate salts are present in a list of ingredients but MSG does not appear to be, the glutamic acid is likely provided as part of another ingredient, such as a processed soy protein complex (hydrolyzed soy protein), autolyzed yeast, or soy sauce.