Taq polymerase - what exonuclease activities?

Wayne J Becktel wbecktel at magnus.acs.ohio-state.edu
Sat Feb 19 09:25:31 EST 1994

In article <1994Feb18.172239.21177 at alw.nih.gov>,
Jim Owens  <jow at helix.nih.gov> wrote:
>In article <CLAF5n.Is6 at massey.ac.nz> P. Hirst, PHirst at massey.ac.nz writes:
>>I'm trying find out exactly what exonuclease activities Taq polymerase
>>has, and which polymerase it is/ or which it's derived from.  The
>>literature I've found so far is far from precise in its description, so
>>any information anyone has would be greatly appreciated.
>According to David Gelfand in Chapter 2 of PCR Technologies: Principles
>and Applications for DNA Amplification, Henry A. Erlich (ed), Stockton
>Press, 1989:
>"Purified 94 kDa Taq DNA polymerase does not contain an inherent 3'-5'
>exonuclease activity...  It is not known if T. aquaticuys contain a
>separate 3'-5' exonuclease activity which may be associated with the
>polymerase in vivo....  Taq DNA polymerase has a DNA synthesis-dependent,
>strand replacement, 5'-3' exonuclease activity.  (more details omitted)"
>Hope this helps,
>Jim Owens

     Taq polymerase has no exonuclease activity.  T7 DNA polymerase does in the
native form but not in the commercial form (Sequenase).  Exo- mutants have also 
been engineered by Patel and Johnson.  Vent polymerase has both polymerase and 
exonuclease activity, and is thermally stable. The advantages of Vent include 
the thermal stability and processivity.

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