Committed step

Schematic representation of a metabolic branch point. The numbers represent chemical compounds, whereas the letters represent enzymes that catalyze the conversion indicated by the nearby arrow. In this scheme, enzyme c catalyzes the committed step in the biosynthesis of compound 6.

In enzymology, the committed step (also known as the first committed step) is an effectively irreversible enzymatic reaction that occurs at a branch point during the biosynthesis of some molecules.[1][2] As the name implies, after this step, the molecules are "committed" to the pathway and will ultimately end up in the pathway's final product. The first committed step should not be confused with the rate-limiting step, which is the step with the highest flux control coefficient. It is rare that the first committed step is in fact the rate-determining step.[3][4]

  1. ^ Bhagavan, N. V. (2002). Medical biochemistry. San Diego: Harcourt/Academic Press. ISBN 0-12-095440-0.
  2. ^ Berg, Jeremy M.; Tymoczko, John L.; Stryer, Lubert (2002). Biochemistry (5th ed.). W. H. Freeman and Company. p. 447. ISBN 0-7167-3051-0.
  3. ^ Sauro, Herbert M. (February 2017). "Control and regulation of pathways via negative feedback". Journal of the Royal Society Interface. 14 (127): 20160848. doi:10.1098/rsif.2016.0848. PMC 5332569. PMID 28202588.
  4. ^ Hofmeyr, Jan-Hendrik S.; Cornish-Bowden, Athel (August 1991). "Quantitative assessment of regulation in metabolic systems". European Journal of Biochemistry. 200 (1): 223–236. doi:10.1111/j.1432-1033.1991.tb21071.x. PMID 1879427.