Quantitation of hyaluronidases by the Morgan–Elson reaction: comparison of the enzyme activities in the plasma of tumor patients and healthy volunteers

The Morgan–Elson reaction, a method for the determination of hyaluronidase activity, was optimized for the quantitation of the enzyme in biological material. Based on HPLC and spectrometric (UV-Vis, LC-MS) studies, the structure of the red-colored product (mesomeric forms of N3-protonated 3-acetylimino-2-(4-dimethylaminophenyl)methylidene-5-(1,2-dihydroxyethyl)furane) formed by condensation of chromogen III with p-dimethylaminobenzaldehyde is proposed. Activities corresponding to ≥0.1 IU of endogenous and therapeutically administered hyaluronidase can be detected in 50 μl samples. Application of the method for the determination of the enzyme in plasma of tumor patients revealed no difference in activity levels, interindividual variability and pH profile compared to healthy volunteers.