Promega Taq, Summary

[Patricia Foster]

Dear Netter,
     My thanks to the many of you who replied on the Net and in Email to my 
query about Promega's Taq.  In summary, let it be said that there is far from a 
consensus about this enzyme.  There are those who swear by it and those who 
have sworn off it.  Instead of giving specific responses, I think I can sort 
the comments into three classes of problems.

1.  Template-primer and preparation specificity.  Of the two enzymes that 
have been discussed (Taq and the Vent family), it appears that even for 
the same user one may work better for a particular application (see John 
Nash's post). So, a wise researcher may wish to keep a couple of enzymes 
around so if one suddenly fails, the other may give results.

2.  Buffer problems.  Promega supplies Taq in two different storage buffers.  
A has NaCl and Triton, B has KCl and Nonidet/Tween.  I have had one strong 
vote for B (Jack Kramer), but it also appears that the buffers may not be 
the same for each lot.  Any more information on this (I need to know -- see 
below)?  As for reaction buffers, the case is mixed -- some people (eg. 
C. Silvia) swear by Promega's (contains Triton and is pH 9.0) and some 
(Jack Kramer) by Cetus' (no detergent and pH 8.3).  So is it possible that 
different opinions about the rxn buffer reflect one person's using storage 
buffer A and the other B?  See the post from Duncan Clark for a home-made 
recipe.

3.  Batch to batch variation.  I have had reports of this about Taq from 
Promega, GIBCO/BRL and BioCan, but not (so far) from Boehringer or Cetus.  
However, I also got a response from the Promega rep (yes, they are 
listening!) and he assures me that Promega stands behind its enzyme as a 
polymerase no matter what the customer chooses to use it for.  It might be 
wise before buying a large amount to check a particular lot and see if you 
can get Promega to sell you more of the same one.

4.  What doesn't seem to be a problem is buying enzyme through Fisher.  
Promega assures me that the enzyme comes directly from them, and there 
doesn't appear to be any consistent relationship between a bad batch and 
buying through Fisher.

     Lastly, as to my particular problem with Promega's Taq, I am working 
with the rep to get it sorted out.  Just in case I am not the only totally 
ignorant purchaser -- BE WARNED -- Promega also sells a sequencing grade Taq, 
which is what I accidentally bought.  I simply didn't know that there was 
more than one enzyme in the catalogue.  Anyway, Promega is sending me a trial 
vial to determine if I can get the non-sequencing grade to work for me.  
But, ah, I have to specify storage buffer A or B!  Help!

Again, many thanks
pat 

Patricia L. Foster
Boston University School of Medicine
Boston, MA USA
pfoster at bu.edu