trypsin

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trypsin,

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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 that acts to degrade proteinprotein,
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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; it is often referred to as a proteolytic enzyme, or proteinase. Trypsin is one of the three principal digestive proteinases, the other two being pepsinpepsin,
enzyme produced in the mucosal lining of the stomach that acts to degrade protein. Pepsin is one of three principal protein-degrading, or proteolytic, enzymes in the digestive system, the other two being chymotrypsin and trypsin.
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 and chymotrypsinchymotrypsin
, proteolytic, or protein-digesting, enzyme active in the mammalian intestinal tract. It catalyzes the hydrolysis of proteins, degrading them into smaller molecules called peptides. Peptides are further split into free amino acids.
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. In the digestive process, trypsin acts with the other proteinases to break down dietary protein molecules to their component peptides and amino acids. Trypsin continues the process of digestion (begun in the stomach) in the small intestine where a slightly alkaline environment (about pH 8) promotes its maximal enzymatic activity. Trypsin, produced in an inactive form by the pancreas, is remarkably similar in chemical composition and in structure to the other chief pancreatic proteinase, chymotrypsin. Both enzymes also appear to have similar mechanisms of action; residues of histidinehistidine
, organic compound, one of the 22 α-amino acids commonly found in animal proteins. Only the l-stereoisomer appears in mammalian protein.
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 and serineserine
, organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer appears in mammalian protein.
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 are found in the active sites of both. The chief difference between the two molecules seems to be in their specificity, that is, each is active only against the peptide bonds in protein molecules that have carboxyl groups donated by certain amino acids. For trypsin these amino acids are arginine and lysine, for chymotrypsin they are tyrosine, phenylalanine, tryptophan, methionine, and leucine. Trypsin is the most discriminating of all the proteolytic enzymes in terms of the restricted number of chemical bonds that it will attack. Good use of this fact has been made by chemists interested in the determination of the amino acid sequence of proteins; trypsin is widely employed as a reagent for the orderly and unambiguous cleavage of such molecules.

Trypsin

 

an enzyme of the hydrolase class that cleaves peptides and proteins and also acts as an esterase—that is, it has the capacity to hydrolyze esters.

Trypsin is synthesized in the pancreas as the inactive precursor (proenzyme) trypsinogen. Samples of the trypsin of a number of animals have been obtained in crystalline form; the first crystalline trypsin was obtained in 1932. The bovine trypsin molecule, with a molecular weight of about 24,000, consists of 223 amino acid residues, which form one polypeptide chain, and contains six disulfide bonds. Its isoelectric point is at pH 10.8, and its optimum catalytic activity is at pH 7.8–8.0. The tertiary structure of trypsin was determined using X-ray diffraction analysis. Trypsin is a serine protease; it contains residues of serine and histidine at its active site. It readily undergoes autolysis, which leads to the contamination of trypsin preparations by inactive products (commercially prepared trypsin contains up to 50 percent inactive impurities). High-purity trypsin preparations are obtained chro-matographically.

Trypsin is capable of converting all the proenzymes of the pancreas (trypsinogen, chymotrypsinogen, and procarboxypeptidase), as well as phospholipase, into active enzymes, and therefore it occupies a key position in the system of digestive enzymes. It is highly specific, selectively hydrolyzing peptide bonds formed by the basic amino acids lysine and arginine. This property permits the broad use of trypsin in the study of the primary structure of insulin, ribonuclease, and other proteins. The activity of trypsin is inhibited by organophosphorus compounds and some metals, as well as by a number of macromolecular protein substances, or trypsin inhibitors, which are present in the tissues of animals, plants, and microorganisms. Ca2+, Mg2+, Ba2+, Sr2+, and Mn2+ ions enhance the hydrolytic activity of trypsin. Enzymes similar to mammalian trypsin have been found in representatives of other classes of vertebrates, as well as in several invertebrates, microorganisms, and some higher plants. Anionic trypsins, which resemble trypsin in a number of their properties but have isoelectric points in more acid media, have been discovered in humans and a number of other mammals.

Trypsin is an anti-inflammatory agent that also acts as an an-tiedemic upon intravenous and intramuscular injection; it is capable of selective removal of tissues that have undergone necrosis. In medicine, trypsin is used for the treatment of wounds, burns, and thromboses, frequently in conjunction with other enzymes and antibiotics.

REFERENCES

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

V. V. MOSOLOV

trypsin

[′trip·sən]
(biochemistry)
A proteolytic enzyme which catalyzes the hydrolysis of peptide linkages in proteins and partially hydrolyzed proteins; derived from trypsinogen by the action of enterokinase in intestinal juice.