Optimization of the USP assay for hyaluronidase

Area of Science:

• Biochemistry
• Enzymology
• Pharmacopeia Standards

Background:

• The United States Pharmacopeia (USP) XXII assay for hyaluronidase (EC 3.2.1.35, HAse) indirectly measures enzyme activity by quantifying residual hyaluronic acid (HA) substrate.
• Hyaluronic acid substrates must pass a USP suitability test to be acceptable for this assay.

Purpose of the Study:

• To evaluate the impact of different hyaluronic acid (HA) substrates on the accuracy and reliability of hyaluronidase (HAse) activity assays.
• To identify the optimal HA substrate for hyaluronidase activity determination.

Main Methods:

• Seven different HA samples, varying in origin, supplier, and chondroitin sulphate content, were tested as substrates.
• Hyaluronidase activity was assayed using testicular hyaluronidases from three suppliers, with USP hyaluronidase reference standard as the benchmark.
• Assay performance was evaluated based on substrate purity, suitability, standard curve linearity, and relative standard deviation.

Main Results:

• Significant variations in calculated hyaluronidase activity were observed depending on the HA substrate used.
• One HA sample failed the USP suitability test but was included to show its effect on the analysis.
• Optimal assay performance, characterized by purity, suitability, linearity, and precision, was achieved using HA derived from vitreous humour.

Conclusions:

• The selection of hyaluronic acid substrate is critical and significantly influences the measured activity of hyaluronidase.
• Hyaluronic acid derived from vitreous humour emerges as the preferred substrate for reliable and accurate hyaluronidase activity assays.
• Adherence to substrate suitability criteria is essential for consistent and reproducible pharmacopeial enzyme assays.