Proenzyme


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proenzyme

[prō′en‚zīm]
(biochemistry)

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.

References in periodicals archive ?
The activity of metalloproteinase 2 is controlled at three levels: at the gene transcription, proenzyme activation and the regulation by tissue inhibitors of metalloproteinases (TIMPs).
Initiator (caspase-9 and -8) and effector caspases (caspase-7, -6, and -3) were determined by Western blot using specific antibodies that bind both the proenzyme and active fragments.
66) The uncovering enzyme is synthesized as a proenzyme and activated after removal of the N-terminal 24 amino acids by furin localized in the trans-Golgi network.
Additionally, the subunit apo A is highly homologous to the fibrinolytic proenzyme plasminogen, and lipoprotein(a) can inhibit plasminogen activation along with its ability to stimulate secretion of plasminogen activator inhibitor-1 (PAI-1).
One form, termed BPSA, is associated with benign prostatic hyperplasia, while proenzyme or precursor forms, termed pPSA, are associated with prostate cancer.
The levels of the proenzyme and activated forms of cathepsin D also increased with increasing hydrogen peroxide concentrations (Figure 2(c)).
The C-terminal region of the heavy chain and the N terminal region of the light chain in the proenzyme resided in a 23-32 residue insert sequence which was not present in other homologs and this region was indicated by homology modeling to form a loop protruding from the remaining part of the enzyme molecule, which should permit the proteolytic cleavage to generate the two chains.
Proenzyme forms of prostate-specific antigen in serum improve the detection of prostate cancer.
Several mechanisms regulate MMP-9 activity, including gene transcription, proenzyme activation, and endogenous inhibitors such as tissue inhibitors of metalloproteinases (TIMPs).
The fibrinolytic (plasminogen/plasmin) system in the vasculature includes an inactive proenzyme, plasminogen (Pg), which can be converted into the active enzyme, plasmin (Pm), which degrades fibrin into soluble degradation products (2).
The conversion of the proenzyme to the active form is an extensively studied system of enzymatic checks and balances known as the phenoloxidase cascade that closely regulates the release and activation of phenoloxidase at the appropriate time and place (Ashida and Yamazaki, 1990; Sugumaran and Kanost, 1993; Soderhall and Cerenius, 1998).