Guanylic acid (GMP)

Guanylic acid is a nucleotide-based umami compound alongside inosinic acid, particularly abundant in dried shiitake mushrooms. It is nearly absent in fresh shiitake—generated when RNA breaks down during drying and heating.

Its synergistic effect with glutamic acid is as powerful as that of inosinic acid. The deep umami of shojin dashi (vegetarian stock from kombu and dried shiitake) comes from the meeting of these two substances.

Intriguingly, the three major umami compounds—glutamic acid, inosinic acid, and guanylic acid—are each abundant in different ingredients. The basic culinary practice of combining different ingredients aligns beautifully with the science of umami.