Aspirin esterase of gastric mucosal origin.

The enzyme, aspirin esterase, which converts acetylsalicyclic acid to the less toxic salicyclic acid, was found to be present in gastric mucosal specimens obtained from surgically resected tissue. The enzyme was found to be stable to storage and active at two pH optima. Alcohol in the reaction mixture produced a net effect of slowing the rate of aspirin hydrolysis; this was attributable to a marked inhibitory effect on aspirin esterase activity which was not completely counteracted by the increased rate of spontaneous breakdown of aspirin by alcohol. Age, sex, or gastric disease state of the patient from whom the tissue was obtained, did not significantly alter the level of enzyme activity measured, nor were different levels obtained from body or antral mucosa. In patients with gastric ulcer, those with a previous history of regular aspirin consumption did not show significantly different levels from those without such a history. It is concluded that aspirin esterase activity of gastric mucosa is not alone a significant factor in any role acetylsalicyclic acid may play in the etiology and natural history of chronic peptic ulcer.