Trypsin

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Trypsin
Identifiers
EC number3.4.21.4
CAS number9002-07-7
Databases
IntEnzIntEnz view
BRENDABRENDA entry
ExPASyNiceZyme view
KEGGKEGG entry
MetaCycmetabolic pathway
PRIAMprofile
PDB structuresRCSB PDB PDBe PDBsum
Gene OntologyAmiGO / EGO
 
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Trypsin
Identifiers
EC number3.4.21.4
CAS number9002-07-7
Databases
IntEnzIntEnz view
BRENDABRENDA entry
ExPASyNiceZyme view
KEGGKEGG entry
MetaCycmetabolic pathway
PRIAMprofile
PDB structuresRCSB PDB PDBe PDBsum
Gene OntologyAmiGO / EGO
Trypsin
1UTN.png
Identifiers
SymbolTrypsin
PfamPF00089
InterProIPR001254
SMARTSM00020
PROSITEPDOC00124
MEROPSS1
SCOP1c2g
SUPERFAMILY1c2g
CDDcd00190

Trypsin (EC 3.4.21.4) is a serine protease from the PA clan superfamily, found in the digestive system of many vertebrates, where it hydrolyses proteins.[2][3] Trypsin is produced in the pancreas as the inactive proenzyme trypsinogen. Trypsin cleaves peptide chains mainly at the carboxyl side of the amino acids lysine or arginine, except when either is followed by proline. It is used for numerous biotechnological processes. The process is commonly referred to as trypsin proteolysis or trypsinisation, and proteins that have been digested/treated with trypsin are said to have been trypsinized.

Function[edit]

In the duodenum, trypsin catalyzes the hydrolysis of peptide bonds, breaking down proteins into smaller peptides. The peptide products are then further hydrolyzed into amino acids via other proteases, rendering them available for absorption into the blood stream. Tryptic digestion is a necessary step in protein absorption as proteins are generally too large to be absorbed through the lining of the small intestine.

Trypsin is produced in the pancreas, in the form of the inactive zymogen trypsinogen. When the pancreas is stimulated by cholecystokinin, it is then secreted into the first part of the small intestine (the duodenum) via the pancreatic duct. Once in the small intestine, the enzyme enteropeptidase activates it into trypsin by proteolytic cleavage. Auto catalysis can happen with trypsin with trypsinogen as the substrate. This activation mechanism is common for most serine proteases, and serves to prevent autodegradation of the pancreas.

Mechanism[edit]

The enzymatic mechanism is similar to that of other serine proteases. These enzymes contain a catalytic triad consisting of histidine-57, aspartate-102, and serine-195.[4] These three residues form a charge relay that serves to make the active site serine nucleophilic. This is achieved by modifying the electrostatic environment of the serine. The enzymatic reaction that trypsin catalyzes is thermodynamically favorable but requires significant activation energy (it is "kinetically unfavorable"). In addition, trypsin contains an "oxyanion hole" formed by the backbone amide hydrogen atoms of Gly-193 and Ser-195, which serves to stabilize the developing negative charge on the carbonyl oxygen atom of the cleaved amides.

The aspartate residue (Asp 189) located in the catalytic pocket (S1) of trypsin is responsible for attracting and stabilizing positively charged lysine and/or arginine, and is, thus, responsible for the specificity of the enzyme. This means that trypsin predominantly cleaves proteins at the carboxyl side (or "C-terminal side") of the amino acids lysine and arginine except when either is bound to a C-terminal proline.,[5] although large-scale mass spectrometry data suggest cleavage occurs even with proline.[6] Trypsin is considered an endopeptidase, i.e., the cleavage occurs within the polypeptide chain rather than at the terminal amino acids located at the ends of polypeptides.

Properties[edit]

Trypsin has an optimal operating pH of about 7.5-8.5 and optimal operating temperature of about 37.1°C.[5]

As a protein trypsin has various molecular weights depending on the source. For example, a molecular weight of 23.3 kDa is reported for trypsin from bovine and porcine sources.


The activity of trypsin is not affected by the enzyme inhibitor tosyl phenylalanyl chloromethyl ketone, TPCK, which deactivates chymotrypsin. This is important because, in some applications, like mass spectrometry, the specificity of cleavage is important.

Trypsin should be stored at very cold temperatures (between −20°C and −80°C) to prevent autolysis, which may also be impeded by storage of trypsin at pH 3 or by using trypsin modified by reductive methylation. When the pH is adjusted back to pH 8, activity returns.

Isozymes[edit]

The following human genes encode proteins with trypsin enzymatic activity:

protease, serine, 1 (trypsin 1)
Identifiers
SymbolPRSS1
Alt. symbolsTRY1
Entrez5644
HUGO9475
OMIM276000
RefSeqNM_002769
UniProtP07477
Other data
LocusChr. 7 q32-qter
protease, serine, 2 (trypsin 2)
Identifiers
SymbolPRSS2
Alt. symbolsTRYP2
Entrez5645
HUGO9483
OMIM601564
RefSeqNM_002770
UniProtP07478
Other data
LocusChr. 7 q35
protease, serine, 3 (mesotrypsin)
Identifiers
SymbolPRSS3
Alt. symbolsPRSS4
Entrez5646
HUGO9486
OMIM613578
RefSeqNM_002771
UniProtP35030
Other data
LocusChr. 9 p13

Other isoforms of trypsin may also be found in other organisms.

Clinical significance[edit]

Activation of trypsin from proteolytic cleavage of trypsinogen in the pancreas can lead to a series of events that cause pancreatic self-digestion, resulting in pancreatitis. One consequence of the autosomal recessive disease cystic fibrosis is a deficiency in transport of trypsin and other digestive enzymes from the pancreas. This leads to the disorder termed meconium ileus. This disorder involves intestinal obstruction (ileus) due to overly thick meconium, which is normally broken down by trypsin and other proteases, then passed in feces.[7]

Applications[edit]

Trypsin is available in high quantity in pancreases, and can be purified rather easily. Hence it has been used widely in various biotechnological processes.

In a tissue culture lab, trypsin is used to re-suspend cells adherent to the cell culture dish wall during the process of harvesting cells.[8] Some cell types have a tendency to "stick" - or adhere - to the sides and bottom of a dish when cultivated in vitro. Trypsin is used to cleave proteins bonding the cultured cells to the dish, so that the cells can be suspended in fresh solution and transferred to fresh dishes.

Trypsin can also be used to dissociate dissected cells (for example, prior to cell fixing and sorting).

Trypsin can be used to break down casein in breast milk. If trypsin is added to a solution of milk powder, the breakdown of casein will cause the milk to become translucent. The rate of reaction can be measured by using the amount of time it takes for the milk to turn translucent.

Trypsin is commonly used in biological research during proteomics experiments to digest proteins into peptides for mass spectrometry analysis, e.g. in-gel digestion. Trypsin is particularly suited for this, since it has a very well defined specificity, as it hydrolyzes only the peptide bonds in which the carbonyl group is contributed either by an Arg or Lys residue.

Trypsin can also be used to dissolve blood clots in its microbial form and treat inflammation in its pancreatic form.

In food[edit]

Commercial protease preparations usually consist of a mixture of various protease enzymes that often includes trypsin. These preparations are widely utilized in food processing:[9]

Trypsin inhibitor[edit]

Main article: Trypsin inhibitor

In order to prevent the action of active trypsin in the pancreas which can be highly damaging, inhibitors such as BPTI and SPINK1 in the pancreas and α1-antitrypsin in the serum are present as part of the defense against its inappropriate activation. Any trypsin prematurely formed from the inactive trypsinogen would be bound by the inhibitor. The protein-protein interaction between trypsin and its inhibitors is one of the tightest found, and trypsin is bound by some of its pancreatic inhibitors essentially irreversibly.[10] In contrast with nearly all known protein assemblies, some complexes of trypsin bound by its inhibitors do not readily dissociate after treatment with 8M urea.[11]

See also[edit]

Trypsinization PA clan of proteases

References[edit]

  1. ^ PDB 1UTN; Leiros HK, Brandsdal BO, Andersen OA, Os V, Leiros I, Helland R, Otlewski J, Willassen NP, Smalås AO (April 2004). "Trypsin specificity as elucidated by LIE calculations, X-ray structures, and association constant measurements". Protein Sci. 13 (4): 1056–70. doi:10.1110/ps.03498604. PMC 2280040. PMID 15044735. 
  2. ^ Rawlings ND, Barrett AJ (1994). "Families of serine peptidases". Meth. Enzymol. Methods in Enzymology 244: 19–61. doi:10.1016/0076-6879(94)44004-2. ISBN 978-0-12-182145-6. PMID 7845208. 
  3. ^ The German physiologist Wilhelm Kühne (1837-1900) discovered trypsin in 1876. See: W. Kühne (1877) "Über das Trypsin (Enzym des Pankreas)", Verhandlungen des naturhistorisch-medicinischen Vereins zu Heidelberg, new series, vol. 1, no. 3, pages 194-198.
  4. ^ Polgár L (October 2005). "The catalytic triad of serine peptidases". Cell. Mol. Life Sci. 62 (19–20): 2161–72. doi:10.1007/s00018-005-5160-x. PMID 16003488. 
  5. ^ a b "Sequencing Grade Modified Trypsin". www.promega.com. 2007-04-01. Retrieved 2009-02-08. 
  6. ^ Rodriguez J, Gupta N, Smith RD, Pevzner PA (2008). "Does trypsin cut before proline?". J. Proteome Res. 7 (1): 300–305. doi:10.1021/pr0705035. PMID 18067249. 
  7. ^ Noone PG, Zhou Z, Silverman LM, Jowell PS, Knowles MR, Cohn JA (December 2001). "Cystic fibrosis gene mutations and pancreatitis risk: relation to epithelial ion transport and trypsin inhibitor gene mutations". Gastroenterology 121 (6): 1310–9. doi:10.1053/gast.2001.29673. PMID 11729110. 
  8. ^ "Trypsin-EDTA (0.25%)". Stem Cell Technologies. Retrieved 2012-02-23. 
  9. ^ "Protease - GMO Database". GMO Compass. European Union. 2010-07-10. Retrieved 2012-01-01. 
  10. ^ Voet & Voet (1995). Biochemisty (2nd ed.). John Wiley & Sons. pp. 396–400. ISBN 0-471-58651-X. 
  11. ^ N. Levilliers, M. Péron, B. Arrio, J. Pudles (October 1970). "On the mechanism of action of proteolyticinhibitors: IV. Effect of 8murea on the stability of trypsin in trypsin-lnhibitor complexes". Archives of Biochemistry and Biophysics 140 (2): 474–483. PMID 5528741. 

External links[edit]

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