MRCP UK EXAMINATIONS

Detailed explanation-1: -Gastric chief cells secrete pepsin as an inactive zymogen called pepsinogen. Parietal cells within the stomach lining secrete hydrochloric acid that lowers the pH of the stomach. A low pH (1.5 to 2) activates pepsin.

Detailed explanation-2: -Effect of pH on substrate hydrolysis by pepsin Pepsin is an aspartic protease and its activity is directly dependent on the pH of the solution environment [41]. At pH values >2.5, pepsin activity begins to decline, with incomplete degradation of the three susceptible substrate proteins by pepsin being observed.

Detailed explanation-3: -Pepsin is an aspartic protease that acts in food digestion in the mammal stomach. An optimal pH of around 2 allows pepsin to operate in its natural acidic environment, while at neutral pH the protein is denatured.

Detailed explanation-4: -At pH below 2.5, conversion of pepsinogen is primarily by an intramolecular mechanism. The propeptide is cleaved monomolecularly at position M16P–E17P, resulting in an active pseudo-enzyme which is enzymatically active and may form a complex with the released pro-segment.

Detailed explanation-5: -Answer and Explanation: High pH indicates an alkaline environment which stabilizes the proenzyme pepsinogen and as such, remains inactive.