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Zymogen

A zymogen (), also called a proenzyme (), is an inactive precursor of an enzyme. A zymogen requires a biochemical change (such as a hydrolysis reaction revealing the active site, or changing the configuration to reveal the active site) for it to become an active enzyme. The biochemical change usually occurs in Golgi bodies, where a specific part of the precursor enzyme is cleaved in order to activate it. The inactivating piece which is cleaved off can be a peptide unit, or can be independently folding domains comprising more than 100 residues. Although they limit the enzyme's ability, these N-terminal extensions of the enzyme or a “prosegment” often aid in the stabilization and folding of the enzyme they inhibit.[citation needed]

The pancreas secretes zymogens partly to prevent the enzymes from digesting proteins in the cells in which they are synthesised. Enzymes like pepsin are created in the form of pepsinogen, an inactive zymogen. Pepsinogen is activated when chief cells release it into the gastric acid, whose hydrochloric acid partially activates it. Another partially inactivated pepsinogen completes the activation by removing the peptide, turning the pepsinogen into pepsin. Accidental activation of zymogens can happen when the secretion duct in the pancreas is blocked by a gallstone, resulting in acute pancreatitis.[citation needed]

Fungi also secrete digestive enzymes into the environment as zymogens. The external environment has a different pH than inside the fungal cell and this changes the zymogen's structure into an active enzyme.[citation needed]

Another way that enzymes can exist in inactive forms and later be converted to active forms is by activating only when a cofactor, called a coenzyme, is bound. In this system, the inactive form (the apoenzyme) becomes the active form (the holoenzyme) when the coenzyme binds.

In the duodenum, the pancreatic zymogens, trypsinogen, chymotrypsinogen, proelastase and procarboxypeptidase are converted into active enzymes by enteropeptidase and trypsin. Chymotrypsinogen, is single polypeptide chain of 245 amino acids residues, is converted to alpha-chymotrypsin, which has three polypeptide chains linked by two of the five disulfide bond present in the primary structure of chymotrypsinogen.

Contents

Examples of zymogens:

  1. "zymogen". Merriam-Webster Dictionary. Retrieved2016-01-24.
  2. "zymogen". Oxford Dictionaries UK Dictionary. Oxford University Press. Retrieved2016-01-24.
  3. "proenzyme". Merriam-Webster Dictionary. Retrieved2016-01-24.
  4. "proenzyme". Oxford Dictionaries UK Dictionary. Oxford University Press. Retrieved2016-01-24.
  5. Dworken, Harvey J. (1982-01-01), Dworken, Harvey J. (ed.), "CHAPTER 4 - Functional Characteristics of the Stomach", Gastroenterology, Butterworth-Heinemann, pp. 85–104, doi:10.1016/b978-0-409-95021-2.50009-1, ISBN 978-0-409-95021-2, retrieved2020-12-15
  6. Mina, Usha; Kumar, Pranav (January 2016). "(PDF) Life Sciences, Fundamentals and Practice, Part I". ResearchGate. Retrieved2020-12-15.
Look up zymogen in Wiktionary, the free dictionary.

Zymogen
Zymogen Language Watch Edit A zymogen ˈ z aɪ m e dʒ en m oʊ 1 2 also called a proenzyme ˌ p r oʊ ˈ ɛ n z aɪ m 3 4 is an inactive precursor of an enzyme A zymogen requires a biochemical change such as a hydrolysis reaction revealing the active site or changing the configuration to reveal the active site for it to become an active enzyme The biochemical change usually occurs in Golgi bodies where a specific part of the precursor enzyme is cleaved in order to activate it The inactivating piece which is cleaved off can be a peptide unit or can be independently folding domains comprising more than 100 residues Although they limit the enzyme s ability these N terminal extensions of the enzyme or a prosegment often aid in the stabilization and folding of the enzyme they inhibit citation needed The pancreas secretes zymogens partly to prevent the enzymes from digesting proteins in the cells in which they are synthesised Enzymes like pepsin are created in the form of pepsinogen an inactive zymogen Pepsinogen is activated when chief cells release it into the gastric acid whose hydrochloric acid partially activates it 5 Another partially inactivated pepsinogen completes the activation by removing the peptide turning the pepsinogen into pepsin Accidental activation of zymogens can happen when the secretion duct in the pancreas is blocked by a gallstone resulting in acute pancreatitis citation needed Fungi also secrete digestive enzymes into the environment as zymogens The external environment has a different pH than inside the fungal cell and this changes the zymogen s structure into an active enzyme citation needed Another way that enzymes can exist in inactive forms and later be converted to active forms is by activating only when a cofactor called a coenzyme is bound In this system the inactive form the apoenzyme becomes the active form the holoenzyme when the coenzyme binds In the duodenum the pancreatic zymogens trypsinogen chymotrypsinogen proelastase and procarboxypeptidase are converted into active enzymes by enteropeptidase and trypsin Chymotrypsinogen is single polypeptide chain of 245 amino acids residues is converted to alpha chymotrypsin which has three polypeptide chains linked by two of the five disulfide bond present in the primary structure of chymotrypsinogen 6 Contents 1 Examples 2 See also 3 References 4 External linksExamples EditExamples of zymogens Angiotensinogen Trypsinogen Chymotrypsinogen Pepsinogen Most proteins in the coagulation system examples prothrombin or plasminogen Some of the proteins of the complement system Procaspases Pacifastin Proelastase Prolipase ProcarboxypolypeptidasesSee also EditEnzyme ProteinReferences Edit zymogen Merriam Webster Dictionary Retrieved 2016 01 24 zymogen Oxford Dictionaries UK Dictionary Oxford University Press Retrieved 2016 01 24 proenzyme Merriam Webster Dictionary Retrieved 2016 01 24 proenzyme Oxford Dictionaries UK Dictionary Oxford University Press Retrieved 2016 01 24 Dworken Harvey J 1982 01 01 Dworken Harvey J ed CHAPTER 4 Functional Characteristics of the Stomach Gastroenterology Butterworth Heinemann pp 85 104 doi 10 1016 b978 0 409 95021 2 50009 1 ISBN 978 0 409 95021 2 retrieved 2020 12 15 Mina Usha Kumar Pranav January 2016 PDF Life Sciences Fundamentals and Practice Part I ResearchGate Retrieved 2020 12 15 External links EditLook up zymogen in Wiktionary the free dictionary Zymogens Washington edu Molecular mechanisms for the conversion of zymogens to active proteolytic enzymes Retrieved from https en wikipedia org w index php title Zymogen amp oldid 1041033498, wikipedia, wiki, book,

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