Serine peptidases are a group of enzymes that play a crucial role in breaking down proteins by cleaving peptide bonds. They are named for the serine amino acid in their active site, which is essential for their catalytic function. These enzymes are found in various organisms, including humans, and are involved in numerous biological processes, such as digestion and immune response. These peptidases can be classified into different families based on their structure and function. Some well-known examples include trypsin and chymotrypsin, which are important for protein digestion in the small intestine. Their activity is tightly regulated to maintain proper physiological balance and prevent unwanted protein degradation.