Unit Definition: Enzyme activity is determined by a change in optical density in a solution of hyaluronic acid. Activity is compared to a hyaluronidase International Standard and is expressed as an International Unit (U).

Hyaluronidase purified from Streptomyes hyalurolyticus is distinct from the known hyaluronidase in its substrate specificity and mechanism of action. This enzyme is quite specific for hyaluronic acid. Various types of chondroitin sulphate (A,B,C,D,E), chondroitin, heparin, keratan sulphate and chitin are not attacked by this enzyme.

Optimum pH: 6,0; Recommended reaction temperature: 60 °C; Inhibitors: Mn²⁺, Hg²⁺, Potassium ferricyanide.