carboxypeptidase-Y

[Valerie]

	Hi,

I am trying to remove a poly-histidine tag off the C-terminal end of a 
protein.  I have tried Carboxypeptidase A and B, both of which cleave the 
histidyl tag, but not beyond the next residue, a proline.  I am now 
trying to use CBP-Y, but I cannot get any activity, not even on the 
histidines.  Even under denaturing conditions (3M urea or 10% methanol, 
pH 5.5) it doesnt seem to touch the protein.  Does anybody have any 
experience with this enzyme?  Any advice would be greatly appreciated.

	Thanks is advance,

	Valerie.