Zymogen
In
The
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, a 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]
Examples
Examples of zymogens:
- 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
- Procarboxypolypeptidases
See also
References
- ^ "zymogen". Merriam-Webster.com Dictionary. Retrieved 2016-01-24.
- ^ "zymogen". Lexico UK English Dictionary. Oxford University Press. Archived from the original on 2020-03-22.
- ^ "proenzyme". Merriam-Webster.com Dictionary. Retrieved 2016-01-24.
- ^ "proenzyme". Lexico UK English Dictionary. Oxford University Press. Archived from the original on 2020-03-22.
- ISBN 978-0-409-95021-2. Retrieved 2020-12-15.
- ^ Mina U, Kumar P (January 2016). "Life Sciences, Fundamentals and Practice, Part I". ResearchGate. Retrieved 2020-12-15.