Neuraminidases or sialidases are exoglycosidases that catalyze the cleavage of a-glycosidically linked terminal N-acetyl neuraminic acid from sialylated glycoconjugates. They are widely spread in nature, occurring in viruses, bacteria, fungi, protozoa, birds and mammals. Together, the neuraminidases form a family of hydrolases that share a conserved active site and similar sequence motifs. Three types of neuraminidase are found in mammals and are defined as lysosomal, plasma membrane and cytosolic on the basis of their biochemical properties and subcellular distribution. Lysosomal N-acetyl-a-neuraminidase (NEU1) has significant primary structure characteristics of other mammalian and microbial sialidases with similar substrate specificity. However, unlike other members of this family, lysosomal neuraminidase requires the carboxypeptidase protective protein/cathepsin A (PPCA) for intracellular transport and lysosomal activation. The enzyme is only catalytically active when it is bound to PPCA and is a component of a high molecular weight, multi-protein complex containing PPCA, ß-galactosidase and N-acetylgalactosamine-6-sulfate sulfatase. The autosomal recessive genetic deficiency of NEU1 is associated with sialidosis, a neurodegenerative lysosomal storage disorder.
This whole rabbit serum was prepared by repeated immunizations with a bacterially expressed and purified fusion protein excluding the signal peptide (first 45 amino acids) and the first 6 N-terminal amino acids of the processed form of human lysosomal neuraminidase.