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 a purine ribonucleoside 5′-monophosphate having guanine as the nucleobase. It is an ester of phosphoric acid with the nucleoside guanosine. It has a role as a metabolite, a biomarker, an Escherichia coli metabolite, and a mouse metabolite. GMP consists of the phosphate group, the pentose sugar ribose, and the nucleobase guanine; hence it is a ribonucleoside monophosphate. It is a guanine nucleotide containing one phosphate group esterified to the sugar moiety and found widely in nature. Guanosine monophosphate is commercially produced by microbial fermentation.
Guanosine monophosphate exists in all living species, ranging from bacteria to humans. It is known as E number reference E626. Cyclic GMP is a cellular regulatory agent that acts as a second messenger. Its levels increase in response to a variety of signals (acetylcholine, insulin, oxytocin) and activates specific protein kinases.
Guanosine monophosphate (GMP) is a nucleoside phosphate in being comprised of a ribonucleoside and one phosphate group. As it is a fairly expensive additive, it is usually not used independently of glutamic acid or monosodium glutamate (MSG), which also contribute umami. The cyclic form of GMP is referred to as cyclic GMP (cGMP). 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. The enzyme guanylyl cyclase catalyzes the conversion of ”guanosine triphosphate (GTP) into cGMP. Its levels increase in response to a variety of hormones, including acetylcholine, insulin, and oxytocin and it has been found to activate specific protein kinases.
Guanosine monophosphate 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.
GMP may also be synthesized for commercial use, particularly by microbial fermentation. Its salts, e.g. disodium guanylate, dipotassium guanylate, and calcium guanylate are used as flavor enhancers
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, savory rice, tinned vegetables, cured meats, and packet soup.