Modification of arginine residues in subtilisins Novo and Carlsberg. Effect on the protein structure and enzymatic activity.

The modification of arginine 186 and arginine 247 in subtilisin Novo as well as the four guanidino groups in subtilisin Carlsberg decreased the catalytic activity. The inactivation proceeded by 60-70% toward casein and by 80% toward p-nitrophenyl acetate during 4 h of incubation with glyoxal. No decrease in the lysyl content was found. The modification had little effect on the fluorescence and circular dichroism properties of the two subtilisins. It was deduced that the inactivation of subtilisins was due to changes in the catalytically active conformation of the active sites, induced by the modification of the arginyl residues. The role of guanidino groups in structure and function of the subtilisins Novo, Carlsberg, DY and mesentericopeptidase is quite similar.