Disodium 5'-ribonucleotides, E number E635, is a flavor enhancer which is synergistic with glutamates in creating the taste of umami. It is a mixture of disodium inosinate (IMP) and disodium guanylate (GMP) and is often used where a food already contains natural glutamates (as in meat extract) or added monosodium glutamate (MSG). It is primarily used in flavored noodles, snack foods, chips, crackers, sauces and fast foods. It is produced by combining the sodium salts of the natural compounds guanylic acid (E626) and inosinic acid (E630). http://www.foodchem.com

A mixture of 98% monosodium glutamate and 2% E635 has four times the flavor enhancing power of monosodium glutamate (MSG) alone