FAMILY-A-CELLULASES - 2 ESSENTIAL TRYPTOPHAN RESIDUES IN ENDOGLUCANASE-III FROM TRICHODERMA-REESEI

Three tryptophan residues are readily oxidised by N-bromosuccinimide in endoglucanase III from Trichorderma reesei. Evidence was obtained that the residue first modified is situated in the cellulose-binding domain and the second in the enzyme's catalytic site. The latter influences the binding and hydrolysis of soluble substrates. The modification of a third residue does not further affect the catalytic properties. The present results complement published data concerning other identified catalytic residues, and help to clarify the active site structure of family A cellulases.