What is the Difference Between Taq Polymerase and Pfu Polymerase

The main difference between Taq polymerase and Pfu polymerase is that Taq polymerase is thermostable, whereas Pfu polymerase, in addition to thermostability, has proofreading properties.

Taq polymerase and Pfu polymerase are two polymerase types in living organisms. They catalyze the synthesis of polynucleotides.

Key Areas Covered

1. What is Taq Polymerase
– Definition, Facts, Features
2. What is Pfu Polymerase
– Definition, Facts, Features
3. Similarities Between Taq Polymerase and Pfu Polymerase
– Outline of Common Features
4. Difference Between Taq Polymerase and Pfu Polymerase
– Comparison of Key Differences
5. FAQ: Taq Polymerase and Pfu Polymerase
– Answers to frequently asked questions

Key Terms  

Pfu Polymerase, Taq Polymerase

What is Taq Polymerase

Taq polymerase is the most common DNA polymerase type used in the PCR amplification of DNA. The main feature of Taq polymerase is that it is heat resistant. It has a half-life of 40 minutes at 95°C. In addition, its optimal temperature is 72°C, and it adds 2–4 kilobases per minute at its optimal temperature. Since it is active in a broad range of temperatures, Taq polymerase adds nucleotides, and if DNA and primers are available, mispriming and elongation may occur.

Figure 1: Full Taq DNA Polymerase Bound to a DNA Octamer

Furthermore, Taq polymerase originates from the thermophilic eubacterial microorganism Thermus aquaticus, which is a bacterium that lives in hot springs and hydrothermal vents. Also, it is an enzyme able to withstand the protein-denaturing conditions (high temperature) required during PCR. Therefore, it replaced the DNA polymerase from E. coli, which was initially used in PCR.

What is Pfu Polymerase

Pfu polymerase is a highly thermostable DNA polymerase occurring naturally in a hyperthermophilic archaeum Pyrococcus furiosus. The template-dependent polymerization of nucleotides in the 5′ to 3′ direction is the primary function of Pfu polymerase. Meanwhile, it exhibits 3′ to 5′ exonuclease (proofreading activity) activity. It corrects the nucleotide incorporation errors. Therefore, the superior thermostability and proofreading activity are the critical features of Pfu polymerase. Hence, Pfu polymerase provides an efficient system for high-fidelity DNA synthesis. It gives the same fidelity and speed when used in conjunction with Taq polymerase.

Figure 2: Pyrococcus furiosus

Moreover, the applications of Pfu polymerase include;

• High-fidelity PCR and primer-extension reactions
• Generation of PCR products for cloning and expression
• PCR cloning and blunt-end amplification product generation
• RT-PCR for cDNA cloning and expression
• Site-directed mutagenesis
• Blunt-end PCR cloning

Similarities Between Taq Polymerase and Pfu Polymerase

• Taq polymerase and Pfu polymerase are two polymerase types important in catalyzing the synthesis of polynucleotide chains.
• Naturally, they occur in prokaryotes.
• They use nucleotides as building blocks for the synthesis of polynucleotides.
• Both are DNA-dependent DNA polymerases.
• They play a crucial role in the multiplication of DNA in cell division.
• Both lack 5′ to 3′ exonuclease activity.

Difference Between Taq Polymerase and Pfu Polymerase

Definition

Taq polymerase refers to the heat-stable (thermostable) DNA polymerase extracted from the thermophilic bacterium Thermus aquaticus. In contrast, Pfu polymerase is an enzyme found in the hyperthermophilic archaeon Pyrococcus furiosus, which functions to copy the organism’s DNA during cell division.

Origin

Taq polymerase occurs in bacterium (Thermus aquaticus), while Pfu polymerase occurs in archaea (Pyrococcus furiosus).

Thermostability (half-life) at 95 °C

The thermostability of Taq polymerase at 95 °C is 1.6 h, while the thermostability of Pfu polymerase at 95 °C is 6 h.

3′ to 5′ Exonuclease Activity

Taq polymerase does not have 3′ to 5′ exonuclease activity, while Pfu polymerase has 3′ to 5′ exonuclease activity.

Fidelity

Taq polymerase shows low fidelity, while Pfu polymerase shows high fidelity.

Processivity

The processivity of Taq polymerase is 22 nt, while the processivity of Pfu polymerase is 6.4 nt.

Elongation Rate

The elongation rate of Taq polymerase is 150 nt/s (75–80 °C), while the elongation rate of Pfu polymerase is 0.2~0.4 kb/min (70~75°C).

Optimal Temperature

The optimal temperature of Taq polymerase is 72°C while the optimal temperature of Pfu polymerase is 70-75°C.

Importance

Taq polymerase is essential for PCR, while Pfu polymerase is necessary for high-fidelity PCR.

FAQ: Taq Polymerase and Pfu Polymerase

Is Pfu faster than Taq? 

The speed of Pfu polymerase is lower than that of the Taq polymerase. However, the combining of Pfu polymerase with Taq polymerase gives the speed of Taq polymerase and the fidelity of Pfu polymerase.    

What is the difference between Taq polymerase and regular polymerase? 

The differentiating factor between Taq polymerase and regular polymerase is the ability to withstand higher temperatures. Importantly, Taq polymerase tolerates higher temperatures without denaturing. 

What are Taq and Pfu polymerase isolated from? 

Both Taq and Pfu polymerases are thermostable polymerases. Therefore, they are isolated from thermophilic bacteria. Naturally, they are DNA polymerases widely used in PCR.

Conclusion

In brief, Taq polymerase and Pfu polymerase are two types of polymerases essential in synthesizing polynucleotides. Taq polymerase occurs in Thermus aquaticus, which is a thermophilic bacterium. It does not have 3′ to 5′ exonuclease activity. Also, it shows a low fidelity but high processivity. The optimal temperature of Taq polymerase is 72°C. In comparison, Pfu polymerase occurs in Pyrococcus furiosus, a hyperthermophilic archaeon. However, it has 3′ to 5′ exonuclease activity. Importantly, it shows a high fidelity but a low processivity. Therefore, the main difference between Taq polymerase and Pfu polymerase is their origin and fidelity. 

References:

1. Pampel, J. (n.d.). Polymerases: Www.genomics-online.com. Polymerases.
2. Pfu DNA Polymerase. MCLAB products. (n.d.). 

Image Courtesy:

1. “Taq” By Adenosine – Own Work (CC BY SA 3.0) via Commons Wikimedia
2. “P furiosus.” By Michelle Kropf – Own Work (CC-BY SA 4.0) via Commons Wikimedia