What are zymogens? How they are formed? What Is a Zymogen? A zymogen is like a wrapped candy bar. In order to get to the good stuff, you need to tear away what's keeping you from it. Zymogens , or proenzymes , are enzymes that aren't functioning yet because their action is infertile by a 'wrapper'. The 'wrapper' can be a link between two amino acids (the building blocks of proteins), like a piece of string keeping a box closed. Or it can be an further section of protein, like a jar lid. How they are formed? When cells make enzymes, especially proteases, they often make them as zymogen, an inactive form of the enzyme. This is so they don't go crazy and are only used when needed. Imagine your reaction if your blender suddenly hopped about on the counter, out of control, spewing half-chopped fruit everywhere. The counter would be a mess, and so would the cell. You can recognize most zymogens by their name. Enzymes that begin with ...