At which pH do enzymes work optimally in the stomach?

Enzymes in the stomach, such as pepsin, function optimally at a low pH, typically around 2.0. This acidic environment is crucial for their activity, as the stomach secretes hydrochloric acid (HCl) to maintain a highly acidic pH that aids in the digestion of proteins. At this low pH, pepsinogen, the inactive precursor of pepsin, is activated to its active form, allowing it to effectively cleave proteins into smaller peptides.

The acidic conditions also help to denature proteins, making them more accessible to enzymatic action. In contrast, other pH levels such as 7.4 (which is neutral and more suited for enzymes in the bloodstream), 4.5 (which is still more alkaline than optimal for stomach enzymes), and 8.5 (which is significantly alkaline) do not provide the necessary conditions for digestive enzymes to operate efficiently in the stomach's environment.