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Articles

Ficin-Catalyzed Reactions. Hydrolysis of -N-Benzoyl-L-Arginine Ethyl Ester and -N-Benzoyl-L-Argininamide ^1,2

^a Department of Food Science and Technology, University of California, Davis, California 95616

The effect of pH on the hydrolysis of -N-benzoyl-L-arginine ethyl ester (BAEE) and -N-benzoyl-L-argininamide (BAA) by a proteolytic enzyme component purified from Ficus carica var. Kadota latex has been studied in detail over the pH range of 3 to 9.5. k_cat (lim) values for the hydrolysis of BAEE and BAA were essentially identical (5.20 and 5.01 sec^–1, respectively at 30°). k_cat values for hydrolysis of BAEE and BAA were dependent on prototropic groups with apparent pK values of 4.24 and 8.53 and 4.10 and 8.59, respectively. k_cat (lim) values for tht hydrolysis of BAEE and BAA were essentially identical (5.20 and groups of pK 4.33 and 8.60 and 4.55 and 8.51, respectively. Thus the pH optimum is 6.5 for both substrates. K_m (app) values for BAEE and BAA were 3.32 x 10^–2M and 6.03 x 10^–2M respectively over the pH range of 3.9 to 8.0. These data are interpreted in terms of the involvement of a carboxyl and a sulfhydryl group in the active center of the enzyme. The data do not support the concept that deacylation of the acyl-enzyme is completely the rate controlling step in the hydrolyses. Rather, it appears that the magnitude of k₂ and k₃ are not greatly different.

⁴ Author to whom reprint requests should be sent.

¹ This work was supported in part by Grant No. GM-05216 from the National Institutes of Health.

² Taken from a thesis presented to the Graduate Division, University of California, Davis, by D. E. Kramer in partial fulfillment of the requirement for the Ph.D. degree 1967.