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Ligase
From Wikipedia, the free encyclopedia
In biochemistry, a ligase (from the Latin verb ligāre — "to bind" or "to glue together") is an enzyme that can catalyse the joining of the sugar phosphate backbones of Okazaki fragments of DNA. Generally ligase catalyses the following reaction:
- Ab + C → A–C + b
or sometimes
- Ab + cD → A–D + b + c
where the lower case letters signify the small, pendant groups.
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The common names of ligase enzymes often include the word "ligase", such as DNA ligase, an enzyme commonly used in molecular biology laboratories to join together DNA fragments. Other common names for ligases include synthetase, because they are used to synthesize new molecules, or carboxylase when they are used to add carbon dioxide to a molecule.
Note that "synthetase" should not be confused with synthases, as synthases do not use adenosine triphosphate and belong to the lyase group, while synthetases do use adenosine triphosphate (ATP).
Ligases are classified as EC 6 in the EC number classification of enzymes. Ligases can be further classified into six subclasses:
- EC 6.1 includes ligases used to form carbon-oxygen bonds
- EC 6.2 includes ligases used to form carbon-sulfur bonds
- EC 6.3 includes ligases used to form carbon-nitrogen bonds (including argininosuccinate synthetase)
- EC 6.4 includes ligases used to form carbon-carbon bonds
- EC 6.5 includes ligases used to form phosphoric ester bonds
- EC 6.6 includes ligases used to form nitrogen-metal bonds
- EC 6 Introduction from the Department of Chemistry at Queen Mary, University of London
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| Topics | Active site - Allosteric regulation - Binding site - Catalytically perfect enzyme - Coenzyme - Cofactor - Cooperativity - EC number Enzyme catalysis - Enzyme inhibitor - Enzyme kinetics - Lineweaver-Burk plot - Michaelis-Menten kinetics - List of enzymes |
| Types | EC1 Oxidoreductases/list - EC2 Transferases/list - EC3 Hydrolases/list - EC4 Lyases/list - EC5 Isomerases/list - EC6 Ligases/list |
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| 6.1 - Carbon-Oxygen | Aminoacyl tRNA synthetase |
| 6.2 - Carbon-Sulfur | Succinyl coenzyme A synthetase - Acetyl Co-A synthetase - Long fatty acyl CoA synthetase |
| 6.3 - Carbon-Nitrogen | Glutamine synthetase - Ubiquitin ligase (Von Hippel-Lindau tumor suppressor, UBE3A, Mdm2, Anaphase-promoting complex) - Glutathione synthetase - CTP synthase - Adenylosuccinate synthase - Argininosuccinate synthetase - Holocarboxylase synthetase - GMP synthase - Asparagine synthetase - Carbamoyl phosphate synthase (I , II ) |
| 6.4 - Carbon-Carbon | Carbon-carbon ligases |
| 6.5 - Phosphoric Ester | DNA ligase |