polymerase

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. During this process, DNA polymerase "reads" the existing DNA strands to create two new strands that match the existing ones.[1][2][3][4][5][6] These enzymes catalyze the chemical reaction

deoxynucleoside triphosphate + DNAn ⇌ pyrophosphate + DNAn+1.
DNA polymerase adds nucleotides to the three prime (3')-end of a DNA strand, one nucleotide at a time. Every time a cell divides, DNA polymerases are required to duplicate the cell's DNA, so that a copy of the original DNA molecule can be passed to each daughter cell. In this way, genetic information is passed down from generation to generation.

Before replication can take place, an enzyme called helicase unwinds the DNA molecule from its tightly woven form, in the process breaking the hydrogen bonds between the nucleotide bases. This opens up or "unzips" the double-stranded DNA to give two single strands of DNA that can be used as templates for replication in the above reaction.

1. DNA polymerase

2. Content Introduction Definition Types Working process Functions

3. Introduction DNA polymerase was first identified by Arthur Kornberg in lysates of Escherichia coli, in 1956. The enzyme is found and used in the DNA replication of both prokaryotic and eukaryotic cells. Several types of DNA polymerase enzymes have been discovered with the first one to be discovered named DNA polymerase I. Each of these types plays a major role in replication and DNA repair mechanisms.

4. Definition “DNA polymerases are enzymes that catalyze the template-directed synthesis of DNA.” DNA polymerases are a group of enzymes that are used to make copies of DNA templates, essentially used in DNA replication mechanisms. These enzymes make new copies of DNA from existing templates and also function by repairing the synthesized DNA to prevent mutations.

5. Types of DNA Polymerase Prokaryotic DNA polymerase: - DNA polymerase l DNA polymerase ll DNA polymerase lll DNA polymerase lV DNA polymerase V

6. DNA polymerase I :-This is a repair polymerase and is involved in excision repair with 3’-5’ and 5’-3’ exonuclease activity and processing of Okazaki fragments generated during lagging strand synthesis. DNA polymerase ll :- Pol II has 3’-5’ exonuclease activity and participates in DNA repair. Pol II is also thought to be a backup to Pol III as it can interact with holoenzyme proteins and assume a high level of processivity. DNA polymerase lll :- is the main enzyme for replication in E.coli. The polymerization and processivity rate is maximum in DNA polymerase III. It also has proofreading 3’→5’ exonuclease activity.DNA polymerase III of E.coli is made up of a total of 13 subunits, which comprises 9 different types of subunits.It consists of two core domains made up of 𝜶, 𝟄, and 𝞱 subunits. It is attached to the 𝝲 complex or clamp-loading complex, which is made up of five subunits, 𝞽2𝝲𝝳𝝳’. Additional subunits 𝟀 and 𝟁 are attached to the clamp-loading complex. 𝞫 subunits make two clamps with a dimer each. They increase the processivity of the DNA polymerase III.

7. Cont…

8. Cont…. DNA Polymerase lV :- DNA polymerase involved in non-targeted mutagenesis. During SOS induction, Pol IV production is increased tenfold and one of the functions during this time is to interfere with Pol III holoenzyme processivity. DNA polymerase V:- Pol V is a Y-family DNA polymerase that is involved in SOS response and translesion synthesis DNA repair mechanisms.

9. How Prokaryotic DNA polymerase works

10. Eukaryotic DNA polymerase :- DNA polymerase a :- Enzyme that makes short segment of initiator DNA during replication of animal chromosomes. DNA polymerase β: -Implicated in repairing DNA, in base excision repair and gap-filling synthesis. DNA polymerase γ: - Replicates and repairs mitochondrial DNA and has proofreading 3’->5’ exonuclease activity. DNA polymerase δ :- Enzyme that makes most of the DNA when animal chromosomes are replicated. DNA polymerase ε: - Also highly possessive and has proofreading 3’->5’ exonuclease activity

11. How eukaryotic DNA polymerase works

12. Functions Replication:- The main function of the DNA polymerase is to synthesize DNA by the process of replication Repair:- s, DNA repair is the continuous process to rectify any errors in the genome due to DNA damage. There are various mechanisms by which DNA is repaired. Proofreading:- DNA polymerases remove incorrect pairs by exonuclease activity. They move one step back and remove the mismatched pair by 3’→5’ exonuclease activity. This is known as proofreading.