A zymogen (or proenzyme) is an inactive enzyme precursor. A zymogen requires a biochemical change (such as a hydrolysis reaction revealing the active site, or changing the configuration to reveal the active site) for it to become an active enzyme. The biochemical change usually occurs in a lysosome where a specific part of the precursor enzyme is cleaved in order to activate it. The amino acid chain that is released upon activation is called the activation peptide.

Examples

Examples of zymogens:

• Trypsinogen
• Chymotrypsinogen
• Pepsinogen
• Most proteins in the coagulation system
• Some of the proteins of the complement system
• Caspases
• Proelastase
• Prolipase

See also

• Webster entry on zymogen
• Wiktionary entry on zyme/zymogen

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