Question

Which among the following polymerases, has the highest error rate and least fidelity?

• A. Vent polymerase
• B. Pfu polymerase
• C. Taq polymerase
• D. Pwo polymerase

Answer 1

The correct option is B Pfu polymerase

Taq DNA polymerase: Isolated from a thermophilic bacterium called Thermus aquaticus. This is the most commonly used thermostable DNA polymerase enzyme for the process of replication in vitro by PCR.

Pfu, Vent and Pwo DNA polymerases have 3'-5' proofreading activities unlike Taq DNA polymerase, which has only 5'-3' polymerase activity and lacks 3'-5' proofreading activity. This proofreading activity makes the DNA synthesis relatively error free and accurate. Although Taq polymerase is used more often in the polymerase chain reaction but all these three polymerases have error rates significantly lower than the Taq DNA polymerase.

When greater fidelity is required, other thermostable enzymes may have a significant advantage over Taq DNA polymerase.

1. Pfu DNA polymerase is an enzyme found in the hyperthermophilic archaeon Pyrococcus furiosus. Due to its hyper thermotolerance, it is used in place of Taq, to polymerase DNA at a higher temperature and also to obtain high fidelity PCR products. Fidelity in Pfu is due to the proofreading activity of the enzyme in the 3’- 5’ direction, unlike Taq polymerase. The error rate of Pfu is 10 fold lower than that of Taq.
2. Vent DNA polymerase: This is isolated from the thermostable archean Thermococcus litoralis. This enzyme has exonuclease or proofreading activity, hence the fidelity of the PCR product increases.
3. Pwo DNA polymerase is a thermostable DNA polymerase used for PCR. Isolated from the thermophilic archaeon Pyrococcus woesei, it is used much less than that of Taq and Pfu DNA polymerases. It also possess proofreading property.