Anisylazoformylarginine: A superior assay substrate for carboxypeptidase B type enzymes

Anisylazoformylarginine (CH3OC6H4–N=N–CO–Arg–OH) is rapidly hydrolyzed at the acyl-arginine linkage by the zinc-enzyme porcine carboxypeptidase B. The catalytic reaction is readily monitored spectrophotometrically by disappearance of the intense absorption (349 nm, 19,100) of the azo chromophore, which chemically fragments after substrate cleavage.