Proenzyme

zymogen

 or proenzyme

Any of a class of proteins that are secreted by cells and are inactive precursors of enzymes. Transformation into active enzymes occurs as one or more peptide bonds in the zymogen are cleaved. Examples include trypsinogen and chymotrypsinogen, secreted by the pancreas and converted by proteolysis in the small intestine into the active enzymes trypsin and chymotrypsin; and numerous coagulation factors.

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proenzyme [prō′en‚zīm]

(biochemistry)

zymogen

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Proenzyme 

(also proferment, zymogen, preenzyme), an inactive precursor of enzymes. Proenzymes form during the biosynthesis of enzymes. They are converted into active enzymes following limited proteolysis. The fission of usually one of the peptide bonds of the proenzyme molecule, which results in a partial structural change in the molecule, leads to the formation of the enzyme’s active center. Many proteolytics that are present in animals and bacteria, as well as phospholipase, are synthesized as proenzymes. Typical proenzymes include pepsinogen, trypsinogen, and prothrombin. Proenzymes are biologically important because they inhibit premature enzymatic activity in those cells and tissues where there is enzyme biosynthesis.