What is the Difference Between Taq and Pfu Polymerase

The key difference between Taq and Pfu polymerase is that Taq polymerase possesses 5’-3’ exonuclease proofreading activity while Pfu polymerase possesses 3’-5’ exonuclease proofreading activity.

DNA polymerase catalyzes the synthesis of DNA during replication. DNA polymerase utilizes a template DNA strand to synthesize the complementary DNA strand. In addition to its function as a polymerase, it helps in DNA proofreading and damage repair via its exonuclease activity. Taq and Pfu polymerase are two major polymerase enzymes. Taq polymerase belongs to family A, while Pfu polymerase belongs to family B. They are replicative and repair polymerases and play an important role in a polymerase chain reaction (PCR).

CONTENTS

1. Overview and Key Difference
2. What is Taq Polymerase
3. What is Pfu Polymerase
4. Similarities – Taq and Pfu Polymerase
5. Taq vs Pfu Polymerase in Tabular Form
6. Summary – Taq vs Pfu Polymerase

What is Taq polymerase?

Taq polymerase is a thermostable DNA polymerase 1 that is named after its discovery from the thermophilic eubacterial microorganism Thermus aquaticus. T. aquaticus is a bacterium that lives in extremely hot conditions such as hot springs and hydrothermal vents. Taq polymerase is identified as an enzyme resistant to high temperatures; hence it is used widely during PCR. Taq polymerase has a structure similar to E. coli polymerase A. It consists of a functional 5’-3’ exonuclease domain at the end of the amino acid terminal. The remaining two domains act in coordination through coupled domain motion.

The optimum temperature of Taq polymerase for its activity is 75–80 °C. The enzyme has the ability to replicate a 1000 bp strand of DNA in less than ten seconds at 72 °C. At 75–80 °C, the enzyme reaches its optimal polymerization rate, which is 150 nucleotides per second per enzyme molecule. The use of Taq polymerase facilitates high specificity of the primers and reduces the production of non-specific products such as primer dimers.

What is Pfu Polymerase?

Pfu polymerase is an enzyme found in the hyper-thermophilic archaeon Pyrococcus furiosus. It helps to copy the DNA of the organism during cell division. The enzyme belongs to the B family of DNA polymerase and consists of a 3’-5’ exonuclease domain. Similar to Taq polymerase, Pfu polymerase is also used to amplify DNA in PCR.

Pfu polymerase has high thermostable and proofreading properties. The enzyme possesses 3’-5’ exonuclease proofreading activity. Therefore, when the DNA assembles from the 5’-3’ end, the exonuclease activity of Pfu polymerase will help to remove the mismatched nucleotides from 3’ – 5’ direction. As a result, the PCR fragments generated by Pfu polymerase consist of fewer errors. Pfu polymerase also exhibits significantly higher fidelity of replication. However, Pfu polymerase is slower and requires around one to two minutes per cycle for amplification at 72°C.

What are the Similarities Between Taq and Pfu Polymerase?

• Taq and Pfu polymerase are polymerase enzymes.
• Moreover, they are used as enzymes in PCR.
• Taq and Pfu polymerases are thermostable enzymes.
• They are isolated from prokaryotic organisms.
• Both consist of exonuclease proofreading activity.

What is the Difference Between Taq and Pfu Polymerase?

Taq polymerase possesses 5’-3’ exonuclease proofreading activity, while Pfu polymerase possesses 3’-5’ exonuclease proofreading activity. Thus, this is the key difference between Taq and Pfu polymerase. Taq polymerase is named after the bacterium Thermus aquaticus, while Pfu polymerase is named after the archaeon Pyrococcus furiosus. Moreover, Taq polymerase belongs to the DNA polymerase group A while Pfu polymerase belongs to the DNA polymerase group B.

The below infographic presents the differences between Taq and Pfu polymerase in tabular form for side-by-side comparison.

Summary – Taq vs Pfu Polymerase

Taq and Pfu polymerase are two major polymerase enzymes. Taq polymerase possesses 5’-3’ exonuclease proofreading activity, while Pfu polymerase possesses 3’-5’ exonuclease proofreading activity. This is the key difference between Taq and Pfu polymerase. Taq polymerase belongs to family A, whereas Pfu polymerase belongs to family B. So, this summarizes the difference between Taq and Pfu 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, vol. 5.
2. “Pfu DNA Polymerase.” An Overview | ScienceDirect Topics.

Image Courtesy:

1. “PDB 1ktq EBI” By Jawahar Swaminathan and MSD staff at the European Bioinformatics Institute – (Public Domain) via Commons Wikimedia
2. “Pfu Polymerase PCNA complex ribbon 3a2f bio r 500” By RCSB (CC BY-SA 3.0) via Commons Wikimedia