β-Galactosidase-Neuraminidase Deficiency: Restoration of β-Galactosidase Activity by Protease Inhibitors

β-Galactosidase was partially restored by protease inhibitors, leupeptin, chymo-statin and E-64 in cultured fibroblasts from three patients with β-galactosidase-neuraminidase deficiency. Pepstatin did not activate this enzyme. Neuraminidase was not affected by any of these compounds in the culture medium. It was concluded that the activating effect was produced by a specific inhibition of thiol proteases.