View source for Ligase



==Overview==
In [[biochemistry]], a '''ligase''' (from the [[Latin language|Latin]] verb ''ligāre'' &mdash; "to bind" or "to glue together") is an [[enzyme]] that can catalyse the joining of two large molecules by forming a new [[chemical bond]], usually with accompanying [[hydrolysis]] of a small chemical group pendant to one of the larger molecules. Generally ligase catalyses the following reaction:

:Ab + C → A&ndash;C + b

or sometimes

:Ab + cD → A&ndash;D + b + c

where the lower case letters signify the small, pendant groups.

==Nomenclature==
The common names of ligase enzymes often include the word "ligase", such as [[DNA ligase]], an enzyme commonly used in molecular biology [[laboratory|laboratories]] to join together [[DNA]] fragments. Other common names for ligases include '''synthetase''', because they are used to [[synthesis|synthesize]] new molecules, or '''carboxylase''' when they are used to add [[carbon dioxide]] to a molecule.

Note that "synthetase" should not be confused with [[synthase]]s, as synthases do not use adenosine triphosphate and belong to the [[lyase]] group, while synthetases do use [[adenosine triphosphate]] (ATP).

==Classification==
Ligases are classified as '''EC 6''' in the [[EC number]] classification of enzymes. Ligases can be further classified into six subclasses:
*[[:Category:EC 6.1|EC 6.1]] includes ligases used to form carbon-oxygen bonds
*[[:Category:EC 6.2|EC 6.2]] includes ligases used to form carbon-sulfur bonds
*[[:Category:EC 6.3|EC 6.3]] includes ligases used to form carbon-nitrogen bonds (including [[argininosuccinate synthetase]])
*[[:Category:EC 6.4|EC 6.4]] includes ligases used to form carbon-carbon bonds
*[[:Category:EC 6.5|EC 6.5]] includes ligases used to form [[phosphoric ester]] bonds
*[[:Category:EC 6.6|EC 6.6]] includes ligases used to form nitrogen-metal bonds

==See also==
*[[DNA ligase]]

==External links==
* {{McGrawHillAnimation|genetics|Dna%20Replication}}

==References==
* [http://www.chem.qmul.ac.uk/iubmb/enzyme/EC6/intro.html EC 6 Introduction] from the Department of Chemistry at [[Queen Mary, University of London]]

{{Enzymes}}
{{Ligases}}
[[Category:Ligases]]

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[[ur:پیوستگی]]
[[zh:連接酶]]
[[ja:DNAリガーゼ]]
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