Chromogenic peptidase substrates

[Louis Hom]

There are fluorogenic peptidase substrates (e.g., Z-Arg-Arg-AMC) and
chromogenic glycosidase substrates (e.g., X-Gal) but I can't seem to find
any chromogenic peptidase substrates.  Anyone know of a source?  I need it
to go from one color to another, not simply producing soluble color from
precipitable color (a la azocasein).  TIA.
-- 
______________________________________________________________________________
Lou Hom >K'93			     
lhom at ocf.berkeley.edu		
http://www.ocf.berkeley.edu/~lhom/