Tryptophan residues in Hyaluronidase(HAase) were modified by N-bromosuccinimide(NBS). The results indicated that there were eleven tryptophan residues in HAase and one of them was exposed, which was proved to be essential for the activity of the enzyme. The study on fluorescence quenching of HAase showed that KI could not quench all of the fluorescence from Trp residues in HAase . Acrylamide(Acr), a polarized quencher without electronic charge, could quench almost all of the fluorescence from Trp residues in HAase . The collisional quenching constants(K-D) of HAase at different concentrations of Acr were calculated in terms of Stern-Volmer equation. The results implied that some of Trp residues were buried in the interior of HAase, and the Trp residue on the surface of HAase was not located in the hydrophobic pocket.
