sialidase-1; acetylneuraminyl hydrolase; G9 sialidase; lysosomal sialidase; N-acetyl-alpha-neuraminidase 1 (NEU1, NANH)

Function

• catalyzes removal of sialic acid (N-acetylneuramic acid) moities from glycoproteins & glycolipids
• activity dependent on its presence in the multienzyme complex
• appears to have a preference for alpha 2-3 & alpha 2-6 sialyl linkage
• hydrolysis of alpha-(2->3)-, alpha-(2->6)-, alpha-(2->8)- glycosidic linkages of terminal sialic acid residues in oligosaccharides, glycoproteins, glycolipids, colominic acid & synthetic substrates
• phosphorylation of Tyr within the internalization signal results in inhibition of sialidase internalization & persistence on the plasma membrane
• interacts with other proteins in a multienzyme complex
  • cathepsin A (protective protein)
  • beta-galactosidase
  • N-acetylgalactosamine-6-sulfate sulfatase

Kinetic parameters:

• pH dependence: optimum pH is 4.6

Structure

• N-glycosylated
• a C-terminal internalization signal (YGTL) appears to allow targeting of plasma membrane proteins to endosomes
• belongs to the glycosyl hydrolase 33 family
• contains 4 BNR repeats

Compartment

• lysosome membrane, lumenal side; lysosome lumen
• plasma membrane, cytoplasmic vesicle

Expression

• expressed in pancreas > skeletal muscle, kidney, placenta, heart, lung & liver
• weakly expressed in brain

Pathology

• defects in NEU1 are the cause of sialidosis

More general terms

• sialidase
• glycoprotein
• phosphoprotein

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=4758
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:4758
• OMIM: https://mirror.omim.org/entry/256550
• OMIM: https://mirror.omim.org/entry/608272
• UniProt: http://www.uniprot.org/uniprot/Q99519.html