Solubilization and affinity chromatography of a sialidase from human liver

A sialidase, acting on gangliosides and mucus glycoproteins (pH optimum 4.0-4.5) was solubilized by 1% Triton X-100 and short ultrasonication from a crude mitochondrial-lysosomal fraction isolated from human liver. The enzyme was enriched over 1000-fold with the aid of affinity chromatography on equine submandibular gland mucin bound to Sepharose and 20mM Tris/HCl buffer, pH 7.5, as eluent. The sialidase exhibited a molecular mass of about 200 000 Da on Sephadex G-200. On analytical gel electrophoresis, an enzymically active protein band of about 70 000 Da was observed. A sialidase acting on sialyllactose remained in the membrane fraction and could not be solubilized.