beta N-acetyl hexosaminidase beta chain (hexosaminidase-B, HEXB)

Function

• responsible for the degradation of GM2 gangliosides, & a variety of other molecules containing terminal N-acetyl hexosamines, in the brain & other tissues
• hydrolysis of terminal non-reducing N-acetyl- D-hexosamine residues in N-acetyl-beta-D-hexosaminides

Structure

• belongs to the glycosyl hydrolase 20 family
• 3 forms of beta-hexosaminidase:
  • hexosaminidase A is a trimer composed of
    • one alpha chain,
    • one beta-A chain
    • one beta-B chain
  • hexosaminidase B is a tetramer of
    • two beta-A
    • two beta-B chains
  • hexosaminidase S is an homodimer of
    • two alpha chains
• two beta chains are derived from the cleavage of a precursor chain
• some minor isozymes contain less processed forms of the alpha or beta chains
• N-linked glycans at Asn-142 & Asn-190 consist of Man(3)- GlcNAc(2) & Man(5 to 7)-GlcNAc(2), respectively

Compartment

lysosome

Pathology

• defects in HEXB are the cause of Sandhoff disease

Laboratory

• beta-N-acetylhexosaminidase B in serum
• HEXB gene mutation

More general terms

• glycoprotein
• protein subunit

Additional terms

• Sandhoff disease

Component of

• beta N-acetylhexosaminidase

Database

• UniProt: http://www.uniprot.org/uniprot/P07686.html
• OMIM: https://mirror.omim.org/entry/268800
• OMIM: https://mirror.omim.org/entry/606873