How does prilosec, a competitive inhibitor , affect pepsin/protein hydrolysis in the stomach?

I do not know the drug. And the information you provided is a bit scant.

However, you state that it is a competitive inhibitor. The question is, for what? A short googling reveals that it inhibit proton pumps (which are necessary for creating the acididc environment in the stomach), though I did not find any reference whether the mode is competitive. Pepsin, on the other hand, is is a protease that gets secreted in an inactive form (pepsinogen) before cleaved (and thus activated) by HCl. Lack of acids may inhibit that. In addition, its pH optimum is at pH 2 and it starts denaturing at pH 5. Lack of if the production of acid in the stomach is significantly disturbed, it may thus inactivate pepsin.

I apologize for the scant info. Prilosec is a common antiacid and your clarification shedded a little light on the situational question that was posed. Thanks a mill.