Novagen has introduced a fast and accurate recombinant form of DNA polymerase from the thermophile
Thermococcus kodakaraensis. KOD HiFi DNA polymerase has a 3’ to 5’ exonuclease dependent proofreading activity that results in fewer errors during amplification. It is reported to amplify targets with a "superior accuracy" than other high-fidelity DNA polymerases and have an elongation rate 2X higher than regular Taq (and 5X higher than high-fidelity DNA polymerases). In addition, it has a processivity that is 10-15 times higher than other high-fidelity DNA polymerases.
The polymerase comes in 3 different varieties. KOD HiFi is able to amplify targets up to 6kb. KOD HiFi Hotstart comes premixed with 2 monoclonal antibodies against the polymerase and 3’ to 5’ exonuclease activity. It is able to amplify longer targets than regular KOD HiFi (up to 21kb with plasmid DNA template), in addition to having the advantage of room temperature set up and fewer mis-priming problems. KOD XL DNA polymerase is a mixture of KOD HiFi and a mutant form deficient in 3’ to 5’ exonuclease activity that is designed to amplify longer (up to 30kb) and more complex GC rich targets.
The best thing about KOD DNA polymerase is the fast rate of elongation. It is very fast compared to some of the other high-fidelity DNA polymerases that I have used. For instance, to amplify a 6kb target from plasmid DNA using KOD HiFi the elongation time is just 1 minute in total (NOT per kilobase!), so PCR reaction times can be reduced by several hours in some cases. I have used both the KOD HiFi and KOD XL polymerases with good results from both. For smaller templates from plasmid DNA I have used KOD HiFi, but for longer (6kb) and more temperamental targets I have used KOD XL with success. In addition, I have not yet had any nasty surprises when the generated PCR products have been sequenced.
I couldn’t find much to say about KOD DNA polymerase that was bad, since it has worked so well for me. However, because each version is optimized for slightly different applications you could find yourself buying all 3 versions where in the past, with less choice, you would have made do with just one.
Fiona Wardle, Ph.D.
Postdoctoral Associate
Whitehead Institute
Cambridge, MA