Guanosine monophosphate, also known as 5'-guanidylic acid or guanylic acid and abbreviated GMP, is a nucleotide that is found 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. Guanosine monophosphate is produced from dried fish or dried seaweed.
Guanosine monophosphate in the form of its sodium salt disodium guanylate (E627) is a food additive used as a flavor enhancer to provide the umami taste. It is often used in synergy with glutamic acid (monosodium glutamate, MSG). As it is a fairly expensive additive, it is usually not used independently of glutamic acid - if disodium guanylate is present in a list of ingredients but MSG does not appear to be, it is likely that glutamic acid is provided as part of another ingredient such as a processed soy protein complex. It is often added to foods in conjunction 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.