Proteolytic Enzyme

proteolytic enzyme [¦prōd·ē·ə¦lid·ik ′en‚zīm]

(biochemistry)

Any enzyme that catalyzes the breakdown of protein.

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Proteolytic Enzyme 

(also protease), an enzyme of the hydrolase class that is present in all living organisms. Proteolytic enzymes catalyze the hydrolysis of peptide bonds in both cellular and food proteins.

Proteolytic enzymes include peptidases (exopeptidases) and proteinases (endopeptidases). Peptidases primarily hydrolyze external peptide bonds in proteins and peptides, while proteinases hydrolyze the internal bonds. Proteolytic enzymes are subdivided according to the structural characteristics of their active center into metalloenzymes, each containing a metal atom, usually Zn, in its active center, and serine, thiolic (cys-teic), and acidic proteinases. Most of the known peptidases are metalloenzymes. Proteinases are also classed according to substrate specificity, that is, the ability to hydrolyze the bonds between specific amino-acid residues.

The sequence of amino acids in the molecules of a series of proteolytic enzymes has been determined. X-ray diffraction analysis has made it possible to determine the complete three-dimensional structure of several key proteinases, including pepsin, trypsin, and chymotrypsin. Proteolytic enzymes of the pancreas are synthesized in the form of inactive precursors—proenzymes—and therefore do not destroy the proteins of their parent tissue.

Preparations from proteolytic enzymes are used for many purposes; they are used in laboratories to determine the structure of proteins and peptides, in the food-processing industry when making cheese or tenderizing meat, in light industry to remove fur from hides and when bating leather, and in medicine to resorb thrombi and remove cataracts.

REFERENCES

Neurath, H. “Fermenty, perevarivaiushchie belki.” In Molekuly ikletki. Moscow, 1966. (Translated from English.)
Mosolov, V. V. Proteoliticheskie fermenty. Moscow, 1971.

V. V. MOSOLOV