exonukleázok

Exonukleázok are enzymes that break down nucleic acids by removing nucleotides from either the 5' or 3' end of a polynucleotide chain. Unlike endonucleases, which cleave phosphodiester bonds within the nucleic acid strand, exonucleases work exclusively at the termini. They play crucial roles in DNA repair, replication, and degradation processes within cells.

There are two main types of exonucleases based on their directionality. 5' exonucleases remove nucleotides from the 5' end, while 3' exonucleases remove them from the 3' end. Some exonucleases are specific to DNA, while others act on RNA.

In DNA replication, certain exonucleases are involved in proofreading, removing incorrectly incorporated nucleotides. During DNA repair, exonucleases can excise damaged or mismatched DNA segments. In RNA metabolism, exonucleases contribute to the degradation of messenger RNA (mRNA) and other RNA molecules, regulating gene expression.

The activity of exonucleases is often tightly regulated to ensure proper cellular function. Dysregulation of exonuclease activity can lead to genomic instability or improper RNA processing, contributing to various diseases.