Tryptophan(Trp) residues in inulinase were modified by chemical reagent N-bromossuccinimide(NBS).The results of Spande′s method indicate that there were seventeen Trp residues in inulinase and five of them were located on the surface of the enzyme.Three of these Trp residues were none-essential residues which showed the fastest rate by Zhou′s plot.Two relative faster reacting residues were both essential for the activity of the enzyme.The other twelve were the slowest or none-reactive residues for the reaction.The study on fluorescence quenching of inulinase shows that KI could not quench all of the fluorescence from Trp residues in inulinase which indicate that there are two kinds of Trp residues in inulinase acrylamide(Acr),a polarized quencher without electronic charge could quench almost all of the fluorescence from Trp residues in inuoinase while there are still seventy percernt of the activity of the enzyme left.The collisional quenching constants(K_D) of inulinase at different concentrations of Acr were calculated in terms of Stern-Volmer equation.
