Ligase
Inbiochemistry,aligaseis anenzymethat cancatalyzethe joining (ligation) of two molecules by forming a newchemical bond.This is typically viahydrolysisof a small pendant chemical group on one of the molecules, typically resulting in the formation of new C-O, C-S, or C-N bonds. For example,DNA ligasecan join two complementary fragments of nucleic acid by forming phosphodiester bonds, and repair single stranded breaks that arise in double stranded DNA during replication.
In general, a ligase catalyzes the following dehydration reaction, thus joining molecules A and B:
A-OH + B-H → A–B + H2O
Nomenclature
[edit]The naming of ligases is inconsistent and so these enzymes are commonly known by several different names. Generally, the common names of ligases include the word "ligase", such as inDNA ligase,an enzyme commonly used in molecular biologylaboratoriesto join togetherDNAfragments. However, many common names use the term "synthetase" or "synthase" instead, because they are used tosynthesizenew molecules.[1]There are also some ligases that use the name "carboxylase" to indicate that the enzyme specifically catalyzes acarboxylationreaction.
To note: biochemical nomenclature has sometimes distinguished synthetases fromsynthasesand sometimes treated the words assynonyms.[2]Commonly, the two terms are used interchangeably and are both used to describe ligases.
Classification
[edit]Ligases are classified asEC 6in theEC numberclassification of enzymes. Ligases can be further classified into six subclasses:
- EC 6.1includes ligases used to form carbon-oxygen bonds
- EC 6.2includes ligases used to form carbon-sulfur bonds
- EC 6.3includes ligases used to form carbon-nitrogen bonds (includingargininosuccinate synthetase)
- EC 6.4includes ligases used to form carbon-carbon bonds, such asacetyl-CoA carboxylase
- EC 6.5includes ligases used to formphosphoric esterbonds, such asDNA ligase
- EC 6.6includes ligases used to form nitrogen-metal bonds, as in thechelatases
Membrane-associated ligases
[edit]Some ligases associate withbiological membranesasperipheral membrane proteinsor anchored through a singletransmembrane helix,[3]for example certainubiquitin ligaserelated proteins.
Etymology and pronunciation
[edit]The wordligaseusescombining formsoflig-(from theLatinverbligāre,"to bind" or "to tie together" ) +-ase(denoting an enzyme), yielding "binding enzyme".
See also
[edit]
References
[edit]- ^"IntEnz - EC 6".www.ebi.ac.uk.RetrievedMay 2,2023.
- ^"Synthetases - Ligases - Enzymes - Products".www.axonmedchem.com.RetrievedMay 2,2023.
- ^Superfamilies of single-pass transmembrane ligasesinMembranome database
- EC 6 Introductionfrom the Department of Chemistry atQueen Mary, University of London
