Neuraminidase in juvenile calf thymus: determination and characterization by a continuous fluorometric assay procedure.

A continuous fluorometric neuraminidase assay has been developed. Within the pH range optimal for neuraminidases (from 3 to 6) the fluorescence intensity of 4-methylumbelliferone exceeds that of the glycoside 4-methylumbelliferyl-alpha-D-N-acetylneuraminic acid about 50 times (at lambda Ex = 335 nm and lambda Em = 445 nm), allowing the precise, simple and time-saving continuous fluorometric registration of enzymatically released 4-methylumbelliferone. In juvenile calf thymus a neuraminidase consisting of two components differing in pH optima and resistence to freezing and to detergents could be found. A beta-galactosidase activity in juvenile calf thymus could be proved by the same assay procedure using the synthetic substrate 4-methylumbelliferyl-beta-D-galactopyranoside.