The Enzyme That Can Replicate Dna Is Called

The Enzymes that Play A Role in DNA Replication

The enzyme that can replicate DNA is called DNA polymerase, DNA ligase, DNA gyrase, and Helicase. There are 3 types of DNA polymerase enzyme, which are DNA polymerase I, DNA polymerase II, and DNA polymerase III. Below are the enzymes which play a role in the DNA replication.

DNA Polymerase Enzyme I

  • DNA polymerase enzyme I plays a role to eliminate the primary RNA which is attached to the lagging strand DNA and replace it with DNA.
  • It is a polypeptide single chain with BM 109 Kdal.
  • It catalyzes the attachment of the new deoxyribonucleotide units to the beginner DNA chain or primary strand.
  • The speed of catalyzing 10 nucleotides is added every second and every 1 mole of DNA polymerase I.
  • It has 3’-5’ exonuclease activity that is checking the results of polymerization before continuing.
  • It also has 5’-3’ exonuclease activity.

DNA Polymerase Enzyme II

The specific function of DNA polymerase enzyme II has not been clear. It is only known that this enzyme also plays a role in DNA replication. The speed of catalyzing as many as 0.5 nucleotides is added per second and has an activity of 3’-5’ exonuclease.

DNA Polymerase Enzyme III

It is a polymerase that is responsible for invivo replication. DNA polymerase enzyme III is a complex holoenzyme with BM 550.000 consisting of 7 different polypeptides, and carrying 5’-3’ exonuclease activity while others carry 3’-5’ exonuclease activity. One or more other polypeptides bind ATP molecules. While the remaining functions are unknown. 2 holoenzymes complexes may be needed in the replication forks, the speed of catalyzing 150 nucleotides is added per second. The DNA polymerase enzyme III contains Zn2+ ion and requires Mg2+ ion to work.

DNA Ligase Enzyme

    DNA ligase has these characteristics:

  • In the form of a single polypeptide chain BM 77.000
  • It needs an OH group at the end of 3’ free and a phosphate group at the other end of the 5’ chain. The formation of this phosphodiester bond is an endergonic reaction that requires energy.
  • It is able to connect 2 moles of DNA chains which are part of the double helix DNA.

The functions of DNA ligase are below:

  • Repairing the broken chains in duplex DNA
  • Connecting the ends of duplex DNA in order to produce a circular DNA.
  • Connecting the DNA synthesis to the recombination process.
  • Cooperating with the DNA polymerase in the DNA replication.

DNA Gyrase Enzyme

DNA gyrase is included in the topoisomerase type II. It has the function to open supercoiled before the replication takes place. This enzyme is also able to change the relaxed form to be supercoiled by needing ATP.

DNA Helicase Enzyme

The enzyme which opens the DNA segment rotation right in the front of the replication fork is called helicase enzyme. This enzyme binds ATP and a single chain of DNA. There are 2 types of helicase enzyme, one binding to the 5’-3’ lagging strands and moving directions, the other binding to the leading strand chain template and moving in 3’-5’ direction.

Single Strand DNA Binding Protein

As soon as possible after the chain is open, a few moles of certain protein attach themselves very tightly in order to keep the chain from getting close again. This enzyme is called Helix-destabilizing protein or also known as a single strand DNA binding protein. The single strand binding protein in E. Coli is a polypeptide which consists of 177 amino acids. The chains that have been bound by the single strand binding protein become stiff, straight, and have no curve.

Primase Enzyme

DNA moves in the direction of 5’-3’ and only consist of 10 nucleotides. Then at the end of 3’ added deoxyribonucleoside triphosphate by DNA polymerase III enzyme one after another so that it is complete 1000 to 2000 nucleotides. The nucleotides in the primary RNA are removed one by one by the 5’-3’ exonuclease activity.

The Functions of DNA Enzymes

Some people are wondering whether the functions of DNA enzymes are important. Actually, those enzymes mentioned above are really important so that all the process in the body can work perfectly. Here are several functions of DNA enzymes:

  1. Fixing the DNA strands. It is the main function of DNA enzymes because the improvement of DNA should be done correctly.
  2. Copying the code in the DNA. It is a process in the replication of DNA will help the DNA sequence properly and correctly made.
  3. Correcting the DNA strands. Sometimes there are DNA strands which are not proper so that they should be fixed to be perfect.

DNA enzymes are a group of enzymes which are helpful in the process of cell replication. Through the help of those enzymes, some new cells that are beneficial for the human will be formed. The cells need those enzymes mentioned above for regenerating and also translating several codes into the DNA strands. Moreover, the cells also use the enzymes in order to breed and grow.

The basic ingredients for the DNA replication are deoxyribonucleotide 5’ triphosphate, DNA I, DNA II, DNA III, polymerase enzyme, and also ligase enzyme. In order to synthesize DNA, the DNA polymerase I enzyme requires 4 kinds of deoxyribonucleotide 5’ triphosphate or Mg2 + DNA chain beginner (primary chain) ions with 3′-OH free groups and ‘DNA templates’. 5′-3 ‘chain lengthening. Elongation occurs because of the incorporation of 3’-OH in the beginner DNA with the most phosphorus atoms in addition to the deoxyribonucleoside triphosphate added.

About how the replication process takes place, there are 3 hypothesizes about it. The first is a depressive hypothesis. According to this hypothesis, the replication occurs by means of the long-intermittent or fragmented double helix. Then the pieces separate and form new pieces that will be continuous with the old pieces. So that they return into 2 new DNAs that are exactly the same.

The second is a conservative hypothesis. According to this hypothesis, replication occurs by means of the old fixed double helix or unchanging and immediately forms a new double helix. And the third is a semi-conservative hypothesis. According to this, replication is performed by 2 chains of double helix divide. Those are the answers of the enzyme that can replicate DNA is called.