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.
As an acyl substituent, it takes the form of the prefix guanylyl-.
De novo synthesis
GMP synthesis starts with <small>D</small>-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 CO<sub>2</sub>, glutamine, glycine, aspartate and one-carbon derivatives of tetrahydrofolate donating various elements towards the building of the ring.
centre|frameless|673x673pxAs inhibitor of guanosine monophosphate synthesis in experimental models, the glutamine analogue DON can be used.
cGMP
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.<!-- ah well, where else can you find this kind of trivia, if not for hindawi? -->
Industrial production is based on fermentation: a bacterium converts sugars into AICA ribonucleotide, which is then converted chemically to GMP. Tapioca starch is a possible sugar source.
Food additive
Guanosine monophosphate is known as E number reference E626. 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.