A pungent ingredient of mustard, allylisothiocyanate, inhibits (H+ + K+)-ATPase.

Allylisothiocyanate (ANCS) is shown to inhibit (H+ + K+)-ATPase isolated from the parietal cell of hog gastric mucosa. The ATPase is the proton pump in the secretory membrane of the parietal cell and is an essential component of the acid secretory mechanism. Furthermore, ANCS suppresses acid secretion by bullfrog gastric mucosa in vitro. We suggest that one aspect of the stomachic function produced by ANCS-including foods is the suppressive effect of ANCS on the acid secretory mechanism.