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DNA polymerase I (or Pol I) is an enzyme that participates in the process of prokaryotic DNA replication. Discovered by Arthur Kornberg in 1956, [1] it was the first known DNA polymerase (and the first known of any kind of polymerase). It was initially characterized in E. coli and is ubiquitous in prokaryotes.
A DNA polymerase is a member of a family of enzymes that catalyze the synthesis of DNA molecules from nucleoside triphosphates, the molecular precursors of DNA. These enzymes are essential for DNA replication and usually work in groups to create two identical DNA duplexes from a single original DNA duplex.
In E. coli, DNA Pol III is the polymerase enzyme primarily responsible for DNA replication. It assembles into a replication complex at the replication fork that exhibits extremely high processivity, remaining intact for the entire replication cycle. In contrast, DNA Pol I is the enzyme
DNA polymerase delta catalytic subunit (DPOD1) is an enzyme that is encoded in the human by the POLD1 gene, in the DNA polymerase delta complex. [5] [6] [7] DPOD1 is responsible for synthesizing the lagging strand of DNA, and has also been implicated in some activities at the leading strand (Figure 1).
Structure of Taq DNA polymerase. In biochemistry, a polymerase is an enzyme (EC 2.7.7.6/7/19/48/49) that synthesizes long chains of polymers or nucleic acids. DNA polymerase and RNA polymerase are used to assemble DNA and RNA molecules, respectively, by copying a DNA template strand using base-pairing interactions or RNA by half ladder replication.
DNA polymerase I also has 3' to 5' and 5' to 3' exonuclease activity, which is used in editing and proofreading DNA for errors. The 3' to 5' can only remove one mononucleotide at a time, and the 5' to 3' activity can remove mononucleotides or up to 10 nucleotides at a time.
The Klenow fragment is a large protein fragment produced when DNA polymerase I from E. coli is enzymatically cleaved by the protease subtilisin.First reported in 1970, [1] it retains the 5' → 3' polymerase activity and the 3’ → 5’ exonuclease activity for removal of precoding nucleotides and proofreading, but loses its 5' → 3' exonuclease activity.
For each of the two DNA strands, two partial probes are ligated to form the actual one; thus, LCR uses two enzymes: a DNA polymerase (used for initial template amplification and then inactivated) and a thermostable DNA ligase. [3]