Carboxylation

Carboxylation in chemistry is a chemical reaction in which a carboxylic acid group is introduced in a substrate. The opposite reaction is decarboxylation.

Carboxylation in organic chemistry

In organic chemistry many different protocols exist for carboxylation. One general approach is by reaction of nucleophiles with dry ice (solid carbon dioxide) ["REGIO- AND STEREOSELECTIVE CARBOXYLATION OFALLYLIC BARIUM REAGENTS: (E)-4,8-DIMETHYL-3,7-NONADIENOIC ACID" Akira Yanagisawa, Katsutaka Yasue, and Hisashi Yamamoto1 Organic Syntheses, Coll. Vol. 9, p.317 (1998); Vol. 74, p.178 (1997) [http://www.orgsynth.org/orgsyn/pdfs/CV9P0317.pdf link] .] or formic acid ["1-ADAMANTANECARBOXYLIC ACID" H. Koch and W. Haaf Organic Syntheses, Coll. Vol. 5, p.20 (1973); Vol. 44, p.1 (1964) [http://www.orgsynth.org/orgsyn/pdfs/CV5P0020.pdf Link] .] ["1-METHYLCYCLOHEXANECARBOXYLIC ACID" W. Haaf Organic Syntheses, Coll. Vol. 5, p.739 (1973); Vol. 46, p.72 (1966).]

Carboxylation in biochemistry

Carboxylation in biochemistry is a posttranslational modification of glutamate residues in proteins. It occurs primarily in proteins involved in the blood clotting cascade, specifically factors II, VII, IX, and X, protein C, and protein S, and also in some bone proteins. This modification is required for these proteins to function. Carboxylation occurs in the liver and is performed by γ-glutamyl carboxylase. [OMIM - gamma-glutamyl carboxylase, contributed by McKusick VA, last updated October 2004 [http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=137167] ]

The carboxylase requires vitamin K as a cofactor and performs the reaction in a processive manner. [cite journal |author=Morris DP, Stevens RD, Wright DJ, Stafford DW |title=Processive post-translational modification. Vitamin K-dependent carboxylation of a peptide substrate |journal=J. Biol. Chem. |volume=270 |issue=51 |pages=30491–8 |year=1995 |pmid=8530480 |doi=] γ-carboxyglutamate binds calcium, which is essential for its activity. [cite journal |author=Hauschka PV, Lian JB, Gallop PM |title=Direct identification of the calcium-binding amino acid, gamma-carboxyglutamate, in mineralized tissue |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=72 |issue=10 |pages=3925–9 |year=1975 |pmid=1060074 |doi=] For example, in prothrombin, calcium binding allows the protein to associate with the plasma membrane in platelets, bringing it into close proximity with the proteins that cleave prothrombin to active thrombin after injury. [Berg JM, Tymoczko JL, Stryer L. "Biochemistry", 5^th ed. New York: W. H. Freeman and Company, 2002.]

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