FLUOROMETRIC ASSAY OF NEURAMINIDASE WITH A SODIUM (4-METHYLUMBELLIFERYL-ALPHA-D-N-ACETYLNEURAMINATE) SUBSTRATE

This report describes the preparation of a sodium (4-methylumbelliferyl-α-d-N-acetylneuraminate) substrate and its use in a sensitive fluorometric assay of neuraminidase (EC 3.2.1.18) from Vibrio cholerae, cultured fibroblasts, and human leucocytes. V. cholerae neuraminidase showed maximum activity at pH 4.6 and an apparent Km of 1.5 mm and was activated by CaCl2 and inhibited by ethylenediaminetetraacetate, NaCl, and N-acetylneuraminic acid. The inhibition by N-acetylneuraminic acid was competitive (Ki = 6.1 mm). Cultured fibroblast and leucocyte neuraminidases showed maximum activity between pH 4.2 and 4.4 and apparent Km values of 0.13 and 0.22 mm, respectively. Neuraminidase activity was considerably reduced in cultured fibroblasts of patients with mucolipidosis types I, II, and III. © 1979.