Enzymes used in PCRSeveral types of thermostable DNA polymerases are available for use in PCR, providing a choice of enzymatic properties, see table DNA polymerases used in PCR.
Taq DNA polymerase
Taq DNA polymerase, isolated from the eubacterium Thermus aquaticus, is the most commonly used enzyme for standard end-point PCR. The robustness of this enzyme allows its use in many different PCR assays. However, as this enzyme is active at room temperature, it is necessary to perform reaction setup on ice to avoid nonspecific amplification.
A number of modifications of the original “PCR polymerase” — Taq DNA polymerase — are now available for different downstream application needs, such as hot-start, single-cell, high-fidelity, or multiplex PCR. With an average error rate of 1 in 10,000 nucleotides, Taq DNA polymerase and its variants are less accurate than thermostable enzymes of DNA polymerase family B. However, due to its versatility, Taq DNA polymerase is still the enzyme of choice for most routine applications and when used with a stringent hot-start, is suitable for several challenging PCR applications.
DNA polymerases used in PCR
|Enzyme properties||DNA polymerase
|Available enzymes||Taq DNA polymerase||Proofreading enzymes
|5'–3' exonuclease activity||+||–|
|3'–5' exonuclease activity||–||+
(per bp/per cycle)
|1 in 103 / 104||1 in 105 / 106
|PCR applications||Standard, hot-start,
|High fidelity, cloning,