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Ligase

A ligase is an enzyme that acts as a catalyst for the joining of two molecules. It performs this ligation by enabling them to form a new chemical bond, and often involves simultaneous hydrolysis of ATP or a similar molecule.

Ligases are classed into six subclasses:

· EC 6.1 ligases form carbon-oxygen bonds
· EC 6.2 ligases form carbon-sulfur bonds
· EC 6.3 ligases form carbon-nitrogen bonds
· EC 6.4 ligases form carbon-carbon bonds
· EC 6.5 ligases form phosphoric ester bonds
· EC 6.6 ligases form nitrogen-metal bonds

When working with DNA, ligases catalyze phosphodiester bonds between the 5' phosphate of a strand of DNA to the 3' hydroxyl of the other. This links two strands of DNA together. DNA ligases may also bind a DNA fragment into a plasmid vector, a primary technique when creating recombinant DNA.

The most popular DNA ligase comes from the T4 bacteriophage; it uses ATP as its cofactor. It is also possible to use a DNA ligase from E. coli using NAD as a cofactor, but it isn't often used.

Web Resources On Ligase

DNA Ligase
T4 DNA Ligases

Book Resources On Ligase

Class 6: Ligases by Schomburg & Schomburg (Editors)
Methods of Enzymatic Analysis, Enzymes 2: Esterases, Glycosidases, Lyases, Ligases by Bergmeyer et al.

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