rekombinase

Rekombinase, or recombinase in English, is an enzyme that catalyzes genetic recombination—the rearrangement of DNA sequences. Recombinases recognize specific DNA motifs and mediate DNA cleavage and rejoining to exchange, insert, delete, or invert segments of DNA. This activity is essential for processes ranging from phage integration to somatic immune system diversification, and it is harnessed in molecular biology to engineer genomes.

Recombinases are commonly grouped into site-specific recombinases, which act at defined short DNA sites (for example loxP, FRT, att sites), and general or homologous recombinases, which mediate exchange between longer homologous sequences. Mechanistically, recombinases fall into two main families: serine recombinases and tyrosine recombinases. Serine recombinases cleave and rejoin DNA via double-strand breaks in a concerted reaction; tyrosine recombinases form a Holliday junction intermediate during strand exchange.

In biology, recombinases drive genome evolution and maintenance. Bacteria and bacteriophages use site-specific recombinases for integration and excision of mobile elements. In vertebrates, the RAG1/RAG2 recombinases initiate V(D)J recombination for adaptive immunity; meiosis and DNA repair also involve recombination pathways using related enzymes such as RecA-like or Rad51 homologs.

In biotechnology, recombinases enable controlled genome modification. The Cre-loxP and Flp-FRT systems are widely used to induce conditional gene knockouts, inversions, or cassette exchanges in model organisms and cell lines. Site-specific integrases (e.g., phiC31) enable targeted DNA integration, while recombinase-mediated cassette exchange and other RMCE approaches allow modular genome engineering without double-strand breaks required by some nuclease-based methods.

Commonly cited examples include Cre recombinase (tyrosine family acting on loxP), Flp recombinase (tyrosine family on FRT), lambda integrase (tyrosine family on att sites), and various serine recombinases used for plasmid or transposon rearrangements.