Inositiol 1,4,5 triphosphate

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Inisitol 1,4,5-triphosphate (IP3) is a water- soluble molecule, which is an intracellular mediator and a secondary messenger [1]. It is responsible for increasing the concentration of Ca2+.

IP3 is produced when phospholipase C, a plasma bound enzyme, is activated by the alpha subunit of a trimeric G protein[2] called Gq. The enzyme then cleaves a phosphorylated inositol phospholipid, called phosphatidylinositol 4,5-biphosphate (PIP2), producing IP3 and diacylglycerol as the two products [3].  

IP3 diffuses through the cytosol and into the endoplasmic reticulum (ER), where it binds to IP3- gated Ca2+- release channels (ligand-gated ion channels[4]) , which are also called IP3 receptors [5]. This causes stored Ca2+ to be released, increasing its concentration. The rise in Ca2+ concentration, along with the second product diacylglycerol, helps to activate protein kinase C, which phosphorylates certain target proteins[6].

References

  1. Unknown. (Undated). Second Messengers: IP3 and DAG. Available: http://courses.washington.edu/conj/gprotein/ip3.htm. Last accessed 28 Nov 2013.
  2. Unknown. (Undated). Second Messengers: IP3 and DAG. Available: http://courses.washington.edu/conj/gprotein/ip3.htm. Last accessed 28 Nov 2013.
  3. Alberts, B et al (2008). Molecular Biology of the Cell. 5th ed. New York: Garland Science. p909-p911
  4. Unknown. (Undated). Second Messengers: IP3 and DAG. Available: http://courses.washington.edu/conj/gprotein/ip3.htm. Last accessed 28 Nov 2013.
  5. Alberts, B et al (2008). Molecular Biology of the Cell. 5th ed. New York: Garland Science. p909-p911
  6. Alberts, B et al (2008). Molecular Biology of the Cell. 5th ed. New York: Garland Science. p909-p911.
 
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