What is a Zymogen?
A zymogen is the inactive precursor of an enzyme. The molecule is composed of amino acids strung together into a peptide. When the zymogen is in the presence of an enzyme specifically designed to breakdown peptides, called a protease, some of the amino acids are removed. This cleavage renders the zymogen a functional enzyme by changing the shape of the peptide and forming the active site where enzymatic action will occur. For this reason, a zymogen is also called a proenzyme. The active site is the key feature of an enzyme. It is the place where the molecule that the enzyme acts on, called the substrate, binds and undergoes chemical change. An enzyme’s active site and overall function is dependent on the shape of the enzyme. This is determined by four structural levels. The primary structure of an enzyme is simply the sequence of amino acids. The secondary structure represents how the peptide folds and twists on itself due to interactions between the amino acids. Secondary structures i
