Driving Carboxypeptidases backwards

[Lauge Schaffer]

Jennifer L. Potter wrote:

> I am thinking about adding a C-terminal tyrosine onto my protein of
> interest.  To bypass all of the molecular biology, it was suggested
> that I simply drive a carboxypeptidase (probably either A or Y) reaction
> backwards to ADD a tyr instead of cleave the C-terminal residue (a Ser).

Enzymatic coupling has been used extensively for trypsin.
In this case you drive the reaction by running it in about 70% organic 
solvent (e.g. DMF/DMSO/1,4-Butanediol) which shifts the equilibrium 
towards synthesis.
I don't know whether CpA or CpY works the same way (how about a little 
trip to the library?)

Lauge