DNA ligase is an enzyme essential for DNA replication and repair.
It catalyzes the formation of phosphodiester bonds between adjacent nucleotides, sealing breaks in the sugar-phosphate backbone of DNA.
Mechanism of Action
Catalyzes the formation of phosphodiester bonds between 3'-OH and 5'-phosphate ends of DNA strands.
Requires ATP or NAD+ as an energy source.
Specificity
Highly specific for joining complementary DNA strands at the break site.
Can distinguish between single-stranded and double-stranded DNA ends.
Applications
Used in molecular biology and genetic engineering techniques:
DNA cloning – joins compatible DNA fragments to form recombinant DNA.
Gene synthesis, site-directed mutagenesis, and DNA sequencing.
Types of DNA Ligase
A) Eukaryotic Types
DNA Ligase I – Involved in DNA replication.
DNA Ligase III – Functions in DNA repair.
DNA Ligase IV – Involved in double-strand break repair.
B) Prokaryotic DNA Ligase
A single type, similar in function to DNA Ligase I in eukaryotes.
