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(kī'mōtrĭp`sĭn), proteolytic, or protein-digesting, enzymeenzyme,
biological catalyst. The term enzyme comes from zymosis, the Greek word for fermentation, a process accomplished by yeast cells and long known to the brewing industry, which occupied the attention of many 19th-century chemists.
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 active in the mammalian intestinal tract. It catalyzes the hydrolysishydrolysis
, chemical reaction of a compound with water, usually resulting in the formation of one or more new compounds. The most common hydrolysis occurs when a salt of a weak acid or weak base (or both) is dissolved in water.
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 of proteinsprotein,
any of the group of highly complex organic compounds found in all living cells and comprising the most abundant class of all biological molecules. Protein comprises approximately 50% of cellular dry weight.
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, degrading them into smaller molecules called peptidespeptide,
organic compound composed of amino acids linked together chemically by peptide bonds. The peptide bond always involves a single covalent link between the α-carboxyl (oxygen-bearing carbon) of one amino acid and the amino nitrogen of a second amino acid.
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. Peptides are further split into free amino acidsamino acid
, any one of a class of simple organic compounds containing carbon, hydrogen, oxygen, nitrogen, and in certain cases sulfur. These compounds are the building blocks of proteins.
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. Chymotrypsin is produced in the pancreas as the inactive, or zymogen, form chymotrypsinogen. Along with other digestive enzymes of the pancreas, chymotrypsinogen is carried in the pancreatic juicepancreatic juice
, secretions of the exocrine portion of the pancreas into the small intestine. The juice contains a number of important digestive enzymes, including trypsin, chymotrypsin, carboxypeptidase, lipase, and amylase.
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 through the pancreatic duct into the duodenum. There chymotrypsinogen is activated by another enzyme, trypsin, and by molecules of active chymotrypsin. Partly because it was one of the first enzymes available commercially in crystalline form, chymotrypsin has been studied extensively.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



an enzyme of the hydrolase class that decomposes proteins and peptides. Chymotrypsin, which is contained in the pancreatic secretions of animals and man, participates, along with trypsin, in the decomposition of food proteins in the small intestine. It is synthesized by the cells of the pancreas in the form of the proenzyme chymotrypsinogen, which is converted under the action of trypsin in the intestine into active chymotrypsin. The activation process includes the splitting of one strictly determined peptide bond in the chymotrypsinogen molecule, which results in the conformational restructuring of the protein molecule and the final formation of the active center of chymotrypsin.

Various forms of chymotrypsin, such as chymotrypsin A, B, and C in certain mammals, have been described, differing in physicochemical properties and certain substrate specificities. Bovine chymotrypsin A, which has a molecular weight of 25,000, was obtained in crystalline form by the American chemists M. Kunitz and J. Northrop in 1935. The molecule consists of 245 amino-acid residues, which are wound into a compact globule with semiaxes measuring 33 and 16.5 angstroms. The three-dimensional structure of chymotrypsin was established by the British scientist D. Blow and his co-workers in 1967 by X-ray diffraction analysis. Numerous forms of chymotrypsin may also be formed in the process of activating chymotrypsinogen, such as the π, δ, and α forms of chymotrypsin A of cattle.

Chymotrypsin belongs to the group of serine proteinases. Its active center includes serine residues, as well as asparaginic-acid and histidine residues, which form a charge-transfer complex. As a result of the transfer of a proton from the serine residue to histidine and then from histidine to an asparaginic-acid residue, there is a negative charge on the serine residue, which acquires the ability to attack the carbonyl carbon of the hydrolyzed peptide bond. Chymotrypsin acts in an alkaline medium (pH 7.0–8.5) and splits primarily the bonds in proteins and peptides that are formed by aromatic amino acids-tyrosine, phenylalanine, and tryptophan.

Chymotrypsin has a milk-clotting action. Chymotrypsin-type enzymes have been found in lower vertebrates and insects.


Northrop, D., M. Kunitz, and R. Herriott. Kristallicheskie fermenty. Moscow, 1950. (Translated from English.)
Mosolov, V. V. Proteoliticheskie fermenty. Moscow, 1971.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


A proteinase in the pancreatic juice that clots milk and hydrolyzes casein and gelatin.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Protein hydrolysis: Casein ([alpha]s1) was hydrolyzed first by pepsin subsequently adding trypsin and chymotrypsin enzymes.
Trypsin and chymotrypsin activities were measured in vitro using the chromogenic synthetic substrates for trypsin and chymotrypsin, N-a-benzoyl-l-arginine-[rho]-nitroanilide (BApNA) and N-succinyl-ala-ala-pro-phe-[rho]-nitroanilide (SAAPFpNA), respectively.
We found statistically significant correlations between increased resistance to 5-fluorocytosine and higher enzymatic activity of chymotrypsin and alpha-mannosidase; increased resistance to miconazole and higher enzymatic activity of beta-glucuronidase; increased susceptibility to miconazole and higher enzymatic activity of leucine arylamidase and acid phosphatase; increased susceptibility to itraconazole and higher enzymatic activity of lipase.
Moreover, the selectivity of the active extracts toward HCV NS3/4A protease (viral protease) and not human serine proteases such as trypsin and chymotrypsin has been confirmed through investigating the inhibitory activity of these extracts and/or their isolated chemical constituents on Human recombinant Trypsin.
* Proteolytic enzymes, including trypsin, chymotrypsin, and bromelain.
The first studies of proteinases, mainly trypsin and chymotrypsin in vertebrate species, were carried out during the first part of the 20th century, describing kinetic properties, isolation and some molecular characteristics (Muhlia-Almazan et al., 2008).
Trypsin, chymotrypsin, amylase and maltase were determined in homogenates from the stomach and anterior, mid and posterior intestine.
Chymotrypsin activity increased at the third protozoeal stage, then significantly decreased in subsequent stages.
Physiologically, autolysis by trypsin and chymotrypsin C (CTRC) and inhibition of trypsin by the trypsin inhibitor (serine protease inhibitor Kazal type 1 (SPINK1)) can protect against trypsin activation [14-16].
In detail, in PSB, compared to PS, the activities of alkaline phosphatase, acid phosphatase, chymotrypsin, trypsin, phosphohydrolase, lipase-esterase, and esterase were increased, while lipase was unchanged (Table 4).