Identification and in Vitro Reconstitution of Lysosomal Neuraminidase from Human Placenta

• Published in: The Journal of biological chemistry Vol. 264; no. 2; pp. 1317 - 1322
• Main Authors: van der Horst, G T J, Galjart, N J, d'Azzo, A, Galjaard, H, Verheijen, F W
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 15-01-1989; American Society for Biochemistry and Molecular Biology
• Subjects: Analytical, structural and metabolic biochemistry; beta-Galactosidase - metabolism; Biological and medical sciences; Chromatography, Affinity; Enzyme Stability; Enzymes and enzyme inhibitors; Female; Fundamental and applied biological sciences. Psychology; Humans; Hydrolases; Immunoblotting; Kinetics; lysosomes; Lysosomes - enzymology; man; Molecular Weight; Neuraminidase - isolation & purification; Neuraminidase - metabolism; placenta; Placenta - enzymology; Pregnancy; Human; Placenta; Purification; Antibody; Gel electrophoresis; Enzyme; Lysosome; Neuraminidase; Immunoblotting assay
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(19)85088-3

Lysosomal neuraminidase from human placenta has been obtained in its active form by association of an inactive neuraminidase polypeptide with β-galactosidase and the protective protein. Using a specific antiserum, we have now identified a 66-kDa protein as the inactive neuraminidase polypeptide. It is specifically recognized on immunoblots only in its nonreduced state, and it coprecipitates with neuraminidase activity. The 66-kDa polypeptide is substantially glycosylated (38-kDa protein core with 7–14 N-linked oligosaccharide chains), a feature characteristic of lysosomal integral membrane proteins. Specific removal of the 66-kDa neuraminidase polypeptide from glycoprotein preparations prevents the generation of neuraminidase activity. Removal of β-galactosidase or destruction of the protective protein also hinders the formation of active neuraminidase. Reconstitution of neuraminidase activity is observed after mixing glycoprotein preparations, depleted in different components of the β-galactosidase-neuraminidase-protective protein complex, indicating that all three components of the complex are required for neuramindase activity. Association of the neuraminidase polypeptide and the protective protein generates unstable neuraminidase activity, whereas association with β-galactosidase is required for stability.