Pfu DNA polymerase
Pfu DNA polymerase is an enzyme found in the hyperthermophilic archaeon Pyrococcus furiosus, where it functions to copy the organism's DNA during cell division. In the laboratory setting, Pfu is used to amplify DNA in the polymerase chain reaction (PCR), where the enzyme serves the central function of copying a new strand of DNA during each extension step.
Proofreading ability of Pfu polymerase
Pfu DNA polymerase has superior thermostability and proofreading properties compared to Taq DNA polymerase. Unlike Taq DNA polymerase, Pfu DNA polymerase possesses 3' to 5' exonuclease proofreading activity, meaning that as the DNA is assembled from the 5' end to 3' end, the exonuclease activity immediately removes nucleotides misincorporated at the 3' end of the growing DNA strand. Consequently, Pfu DNA polymerase-generated PCR fragments will have fewer errors than Taq-generated PCR inserts.
Commercially available Pfu typically results in an error rate of 1 in 1.3 million base pairs and can yield 2.6% mutated products when amplifying 1 kb fragments using PCR. However, Pfu is slower and typically requires 1–2 minutes per cycle to amplify 1kb of DNA at 72 °C. Using Pfu DNA polymerase in PCR reactions also results in blunt-ended PCR products.
Pfu DNA polymerase is hence superior to Taq DNA polymerase for techniques that require high-fidelity DNA synthesis, but can also be used in conjunction with Taq polymerase to obtain the fidelity of Pfu with the speed of Taq polymerase activity..
Scientists associated with the biotech company Stratagene, based in La Jolla, California, discovered the superiority of Pfu over Taq in 1991. They published their work as Lundberg et al., "A High Fidelity Thermostable DNA Polymerase Isolated from Pyrococcus Furiosus," Strategies 4:34-35 (1991) and Gene in December of that year (Gene. 1991 Dec 12;108(1):1-6). U.S. Patent 5,489,523 was granted over exonuclease-deficient Pfu in February 1996 while U.S. and (1991)Patent 5,545,552 over Pfu itself was granted in August 1996.