Proteases of animals
From the table you can see that these exopeptidases and endopeptidases attack specific peptide bonds depending on the chemical group near them. The inactive forms need activators and auto catalysts to convert them into active forms. For example pepsinogen is secreted by the vertebrate stomach. The stomach also secretes HCL which makes the medium acidic (pH 2). This activates pepsinogen into pepsin. Pepsin specifically hydrolyses peptide bond between a dicarboxylic and an aromatic amino acid. In this way short fragments of polypeptide chains are formed. Invertebrates seem to lack pepsin arid their main endopeptidases is more like trypsin. chymotrypsin also attacks a peptide bond involving' aromatic amino acid but on the carboxyl terminal end of the molecule while pepsin attacks on the amino terminal end.