Sialidases 1-4 (NEU1-4, neuraminidases, receptor-destroying enzymes, RDEs) hydrolyse sialic acids (N-acetylneuraminic acid, Neu5Ac) to produce asialo compounds, a step in the degradation process of glycoproteins and gangliosides and are expressed in a variety of cellular locations. NEU4 is an extrinsic membrane protein associated with lysosomes, mitochondria and endoplasmic reticulum. It has broad sialidase activity against glycoconjugates with alpha2,3-, alpha2,6- or alpha2,8-linkages (Bigi et al. 2010, Monti et al. 2004, Seyrantepe et al. 2004). NEU1 (lysosomal sialidase) hydrolyses Neu5Ac from glycoconjugates with alpha2,3-, alpha2,6- or alpha2,8-linked terminal sialated residues in the lysosomal lumen. NEU1 is active in a multienzyme complex comprising cathepsin A protective protein (CTSA) and beta-galactosidase (Bonten et al. 1996, Rudenko et al. 1995). Defects in NEU1 cause Sialidosis (MIM:256550), a lysosomal storage disorder manifesting as type I (late-onset) or type II (earlier-onset) (Bonten et al. 1996). CTSA is thought to exert a protective function necessary for stability and activity of these enzymes (Galjart et al. 1988). Defects in CTSA are the cause of galactosialidosis (GSL; MIM:256540) (Zhou et al. 1991).
Tettamanti, G, Morosi, L, Pozzi, C, Forcella, M, Venerando, B, Monti, E, Fusi, P, Bigi, A
Zanchetti, G, Preti, A, Bassi, MT, Civini, S, Riboni, M, Tettamanti, G, Borsani, G, Monti, E, Venerando, B, Papini, N, Ballabio, A, Bresciani, R, Croci, GL
Landry, K, Hassan, JA, Trudel, S, Pshezhetsky, AV, Seyrantepe, V, Morales, CR
Hol, WG, Rudenko, G, d'Azzo, A, Bonten, E
van der Spoel, A, Grosveld, G, d'Azzo, A, Fornerod, M, Bonten, E
Zhou, XY, Gillemans, N, Willemsen, R, d'Azzo, A, Galjart, NJ, Galjaard, H
Verheijen, FW, Harris, A, van der Horst, GT, Gillemans, N, d'Azzo, A, Galjart, NJ, Galjaard, H
exo-alpha-sialidase activity of NEU4:GLB1:CTSA dimer [lysosomal lumen]
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