First isolated from the bacterial thermophile Thermus aquaticus, the Taq polymerase has become the staple enzyme in molecular biology. Commercial producers have sinced cloned and expressed the enzyme in E. coli. Recombinant Taq is a 94-kDa enzyme with an optimal 5’-3’ polymerase activity between 75-80 °C in the presence of a magnesium cofactor. At 72 °C it can replicate a DNA strand of 1000 base pairs in less than 10 seconds. Taq lacks 3’-5’ exonuclease activity and is prone to errors at a rate around 1 per 3,700 bases. Aside from PCR, Taq is also widely used in TA cloning due to its ability to leave 3’ overhangs. Some commercial modifications to consider include: “High Fidelity” with the recombinant addition of a 3’-5’ proofreading activity, and a “Hot Start” feature to reduce non-specific amplification.
Because each supplier lists quantities as either “units” or “reactions” getting a standardized price that can be used to compare across companies is difficult. Add to that the fact that many companies offer high volume discounts and the fact that high fidelity taq polymerases tend to be more expensive than standard taq and the concept of getting comparable pricing becomes even more daunting. But with those caveats in mind the average price for standard taq polymerases without volume discounts is $0.57 per reaction or $0.32 per unit.