FLUORESCENCE STUDIES ON THE INTERACTION OF DANSYL-L-ARGININE WITH TRYPSIN AND TRYPSINOGEN

The enhancement of fluorescence intensity of the dansyl group due to the formation of [bovine pancreatic] trypsin- or trypsinogen-dansyl-L-arginine complex was measured. Dansyl-L-arginine (L-DA) is a product in the trypsin-catalyzed hydrolysis of dansyl-L-arginine methylester. Trypsinogen had only 1 binding site for L-DA with the dissociation constant of 6.9 .times. 10-3 M, which is identical with the Km for the trypsin-catalyzed hydrolysis of dansyl-L-arginine amide. This finding and the results of X-ray diffraction studies suggest that this binding site is located in the active site of the enzyme. The active enzyme, trypsin, had at least 2 binding sites for L-DA. One is located in the active site. The Kd for L-DA bound to this site is 6.7 .times. 10-3 M. The other site is probably located in the allosteric site of trypsin. The Kd for L-DA bound to this site is 4.8 .times. 10-4 M.