Sialidase 1（NEU1) is a lysosomal enzyme which cleaves terminal sialic acid residues from substrates such as glycoproteins and glycolipids. In the lysosome， the NEU1 enzyme is part of a heterotrimeric complex in cooperation with beta-galactosidase and cathepsin A. NEU1 gene mutations may lead to sialidosis， a lysosomal storage disease that can be the type 1（cherry red -myoclonus syndrome or normosomatic type)， which is late-onset， or the type 2（the dysmorphic type)， which takes place at an earlier age with increased acuteness.
