Key Difference – Taq Polymerase vs DNA Polymerase
DNA polymerase is an enzyme that creates new DNA from its building blocks (nucleotides). In prokaryotes and eukaryotes, different types of DNA polymerases are found. DNA duplication is feasible due to the presence of these special enzymes, and genetic information is passed to the offspring by the action of DNA polymerases. Taq polymerase is a special type of DNA polymerase which is thermostable and is widely used in PCR. Taq polymerase is found in thermophilic bacteria and purified in in vitro DNA replication. The key difference between Taq polymerase and DNA polymerase is that Taq polymerase can withstand high temperatures without denaturing while other DNA polymerases denature at high temperatures (at protein degrading temperatures).
CONTENTS
1. Overview and Key Difference
2. What is Taq Polymerase
3. What is DNA Polymerase
4. Side by Side Comparison – Taq Polymerase vs DNA Polymerase
5. Summary
What is Taq Polymerase?
Taq polymerase (Taq DNA polymerase) is an enzyme used for synthesizing DNA in vitro by PCR technique. It is produced by the thermophilic bacterium called Thermus aquaticus that lives in hot springs and thermal vents. Taq polymerase is a thermostable enzyme which does not degrade at high temperatures. Taq polymerase was purified for the first time and published in Chien et al. in 1976. PCR technique is performed with the aid of Taq polymerase due to its capacity to tolerate high temperature and temperature fluctuations during the PCR. Taq polymerase catalyzes the DNA synthesis when there are primers, nucleotides and the single-stranded template DNA. The enzyme consists of a single polypeptide with a molecular weight of approximately 94 kDa. Taq polymerase shows its optimum activity at 80 °C and at 7 – 8 pH range with the presence of Magnesium ions. It has both polymerase and exonuclease activity. The enzyme is composed of a single polypeptide chain and the gene for Taq polymerase contains high G and C content (67.9%).
Thermostable Taq polymerase allows performing PCR at high temperatures which increase the specificity of primers and reduction of producing unwanted PCR products (primer dimers). Taq polymerase also eliminates the need for adding new enzymes to the PCR reaction after each and every PCR reaction cycle due to its ability to withstand high temperatures. Discovery of Taq polymerase enabled the PCR to perform in a single closed tube in a relatively simple machine. Due to these properties of Taq polymerase, PCR becomes a popular routinely performed laboratory technique in many molecular biology analysis concerning DNA analysis.
Taq polymerase is widely used in molecular biological techniques, and there is a need for large-scale Taq polymerase production. Therefore, using the recombinant DNA technology and gene cloning, the gene that encoded the Taq DNA polymerase had been cloned and expressed in Escherichia coli. This has greatly facilitated the production recombinant Taq polymerase and reduced the price of this enzyme for adequate use.
Figure 1: Taq Polymerase
What is DNA Polymerase?
DNA polymerase is an enzyme which catalyzes the synthesis of DNA from nucleotides. It is the most accurate enzyme responsible for duplicating genomes and passing genetic information to offspring. During cell division, DNA polymerase duplicates all of its DNA and passes one copy to each daughter cell. In 1955, Arthur Kornberg was discovered DNA polymerase in E Coli. The function of DNA polymerase depends on several requirements; template DNA, Mg+2 ions, all four types of deoxynucleotides (dATP, dTTP, dCTP and d GTP), and a short sequence of RNA (primer). Synthesis of the DNA is done in the direction of 5’to 3’ by DNA polymerase.
DNA polymerases can be grouped into seven different families: A, B, C, D, X, Y, and RT (Reverse transcriptase). Retroviruses encode for RT; an unusual DNA polymerase which needs an RNA template for DNA synthesis. There are five different types of DNA polymerases found in prokaryotes for different roles in the DNA replication. DNA polymerase 3 is responsible for the polymerization of the new strand of DNA. DNA polymerase 1 is responsible for repairing and patching DNA. DNA polymerases 2, 4 and 5 are responsible for repairing and proofreading DNA. In eukaryotes, there are 15 distinct types of DNA polymerases. They include five major families.
Figure 2: DNA Polymerase
DNA polymerases are used in gene cloning, PCR, DNA sequencing, SNP detection, molecular diagnostics, etc. Taq polymerase is one kind of a DNA polymerase which can tolerate high temperatures and be available for DNA synthesis without degradation.
What is the difference between Taq Polymerase and DNA Polymerase?
Taq Polymerase vs DNA Polymerase |
|
| Taq DNA polymerase is an enzyme which creates DNA. It is a thermostable enzyme found in thermophiles | DNA polymerase is an enzyme which facilitates the DNA replication and found in both prokaryotic and eukaryotic organisms. |
| Degradation at High Temperatures | |
| Taq polymerase is active at high temperatures. | DNA polymerases degrade at protein denaturing high temperatures. |
| Use | |
| This is widely used in PCR | Taq polymerase replaced theDNA polymerase from coli originally used in PCR. |
Summary – Taq Polymerase vs DNA Polymerase
DNA polymerases are the enzymes that synthesize DNA from deoxynucleotides (building blocks of DNA) when the template and primers are available. DNA polymerases are required to duplicate the cells’ DNA and pass into identical daughter cells during the cell division. DNA polymerases add new nucleotides to the 3’ end of the primer and elongate the new DNA strand synthesis into 5’ to 3’ direction. Taq DNA polymerase is one of a DNA polymerase enzyme which is highly useful in polymerase chain reaction (PCR) method of DNA amplification. E. coli DNA polymerase 1 was used earlier for PCR, but commercial Taq polymerase supplanted it due to its high specificity of primer binding at elevated temperatures and production of a higher yield of the desired product with less non-specific amplification product. This is the difference between Taq Polymerase and DNA Polymerase.
Reference:
1.Ishino, Sonoko, and Yoshizumi Ishino. “DNA polymerases as useful reagents for biotechnology – the history of developmental research in the field.” Frontiers in Microbiology. Frontiers Media S.A., 2014. Web. 28 Feb. 2017
2″Taq and Other Thermostable DNA Polymerases.” Springer. Springer Netherlands, 01 Jan. 1970. Web. 28 Feb. 2017
3.Stillman, Bruce. “DNA polymerases at the replication fork in eukaryotes.” Molecular cell. U.S. National Library of Medicine, 09 May 2008. Web. 28 Feb. 2017
4.EukaryoticDNAPolymerases – University of Oxford.” N.p., n.d. Web. 28 Feb. 2017
Image Courtesy:
1. “Taq”By Adenosine – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “DNA polymerase” By Yikrazuul – Own work (CC BY-SA 3.0) via Commons Wikimedia