even enhanced, the activity on aryl-glucosides. In particular, the kcat of the His 150Ala mutant was 5-fold activated on 2-nitrophenyl-glucoside and the its pH dependence was similar to that of the wild type. These data suggest that in the His 150 residue is not involved in catalysis, but in substrate recognition, perhaps discriminating on the nature of C4 of the sugar moiety. This is the first evidence that this residue plays such a role in glycosyl hydrolase family 1.
1. Aguilar, C., Sanderson, I., Moracci, M., Ciaramella, M., Nucci, R., Rossi, M., and Pearl, L.H. (1997) J. Mol. Biol. 271, 789-802.
2. Moracci, M., Capalbo, L., Ciaramella, M., and Rossi, M. (1996) Protein Eng., 9, 1191-1195.
