proenzyme

n. zymogen, protein that becomes an enzyme under certain conditions (Biochemistry)

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.
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Proenzyme /pro·en·zyme/ an inactive precursor that can be converted to active enzyme. pro·en·zyme n. [more]Proenzyme - Community and Resources

Noun
1. any of a group of compounds that are inactive precursors of enzymes and require some change (such as the hydrolysis of a fragment that masks an active enzyme) to become active
(synonym) zymogen
(hypernym) organic compound

n. proenzyme, zymogen, protein that becomes an enzyme under certain conditions (Biology)