[Structure of the active center of subtilisin 72]

The inhibition by N-benzoyl-L-arginine of subtilisin-catalyzed hydrolysis of various substrates was investigated. Study of combined hydrolysis of these substrates revealed the existence of two productive binding sites in the subtilisin 72 molecule. The type of substrate adsorption depends on the nature of the acyl moiety of the molecule and on the nature of the split-off group. The N-acetyl-L-tyrosine ethyl ester and N-benzoyl-L-citrulline methyl ester are bound at the same adsorption site (A), while N-cinnamoyl imidazole and N-acetyl-L-valine methyl ester are found at another adsorption site (B); N-benzoyl-L-alanine methyl ester can be adsorbed both at site A and at site B. However, substitution of the split-off group in the substrates previously adsorbed at site B by the p-nitrophenyl group causes their transfer to site A.