Hyaluronidase and Hyaluronic Acid

Composed of alternating residues of ß-D-(1-3) glucuronic acid and ß-D-(1-4)-N-Acetylglucosamine
The mammalian hyaluronidases (EC# cleave hyaluronic acid and similar glycosaminoglycans by hydrolysis. The enzyme from Streptomyces (EC# is a lyase that catalyzes cleavage by an elimination reaction yielding a 4-deoxy-4,5-unsaturated oligosaccharides. It’s specificity towards chondroitins and other glycosaminoglycans is unclear.
Hyaluronidase Assays
Prior to 2008 Sigma-Aldrich utilized the Hyaluronidase assay procedure described in the USP (United States Pharmacopoeia XXIII-National Formulary XVIII Combined Edition). The unit activity was defined using a USP standardized hyaluronidase enzyme. This unit was defined as: One unit is based on the change in absorbance at 600 nm (change in turbidity) of a USP reference standard hyaluronidase which is assayed concurrently with each lot of this product.

The USP no longer offers a standardized hyaluronidase enzyme. Sigma-Aldrich has modified the assay method and unit definition to accommodate this unavoidable change. The new unit definition is: One unit will cause a change in A600nm of 0.330 per minute at pH 5.7 at 37 ºC (45 minute assay).

The change in absorbance value of 0.330 in the new unit definition was chosen in order to most closely match the results found using the USP hyaluronidase standard defined activity. As a result, the discontinued USP-based unit definition and the new unit Sigma-Aldrich unit definition will give a conversion factor of approximately 1:1 (One old unit will equal approximately one new unit).