function of DTT

John Richard Seavitt jrseavit at artsci.wustl.edu
Sun Apr 13 12:05:20 EST 1997


On Sat, 12 Apr 1997, Jerry Kropp wrote:

> In article <334EC203.76A3 at med.kuleuven.ac.be>, Peggy De Clercq
> <peggy.declercq at med.kuleuven.ac.be> wrote:
> > Hi,
> > Could anybody tell me the function of DTT (dithiotreitol) in the solution 
> > of several enzymes?
> > Thanks
> > Peggy De Clercq

> Peggy,
> I was taught it helped protect disulfide bonds, thus preserving secondary
> (and tertiary?) structure of the enz. If that's wrong please correct me,
> netters.
> Jerry

Recall that the cytoplasm is a reducing environment (compared to
extracellular compartments), and as a result one would expect generally no 
disulfide bonds in cytoplasmic proteins (though there is evidence for 
their presence in a few apparent exceptions).  Your reasoning is correct
otherwise; reducing agents such as DTT or DTE are added to a number of
enzymatic reactions with the idea that their presence results in a
more-'native' environment (and hopefully, higher and more specific
activity).  Examples include a large number of restriction enzymes,
in-vitro kinase reactions, B-galactose assays, and so forth.  This appears
(to me) to have been determined largely empirically; there are certainly
enzymes of cytoplasmic origin that do not require reducing environments,
and little data demonstrating directly that the presence of a reducing
agent alone correlates with both a change in structure AND enzymatic
activity for most of the enzymes I just mentioned (though this is an area
I'm not at all well-read in).

John Seavitt




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