Activation of human lysosomal sialidase.

An acid sialidase [EC 3.2.1.18], partially purified from human placenta by Con A-Sepharose adsorption and p-aminophenyl thio-beta-D-galactoside-CH-Sepharose (PATG-Sepharose) affinity chromatographies, was activated by incubation at 37 degrees C. This activation showed both time and temperature dependencies, with the most effective activation observed at 37 degrees C in the pH range between 4.3 and 5.2. The influence of various protease inhibitors on its activation was investigated. Among the protease inhibitors tested, amastatin, an inhibitor of aminopeptidase A, significantly inhibited activation. The partially purified enzyme preparation contained aminopeptidase activity, which was inhibited by amastatin. Zinc ions inhibited either the activation of sialidase or the aminopeptidase activity in the enzyme preparation. These results suggest the possibility of participation of aminopeptidase function in the activation process of sialidase.