What substance is primarily involved in the breakdown of food proteins?

The breakdown of food proteins is primarily facilitated by pepsin, which is an enzyme produced in the stomach. Pepsin is secreted in an inactive form known as pepsinogen and is activated by the acidic environment created by gastric acid in the stomach. Once activated, pepsin begins the process of enzymatic digestion by cleaving the peptide bonds in proteins, breaking them down into smaller peptides.

While gastric acid plays an important role in creating the right conditions for pepsin to function, it does not directly break down proteins itself. Similarly, trypsin, which is involved in protein digestion, is active in the small intestine and works on proteins that have already been partially digested by pepsin. Amylase, on the other hand, is involved in the digestion of carbohydrates, not proteins. This makes pepsin the primary enzyme responsible for the initial stages of protein breakdown in the digestive system.