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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:
a) hexosaminidase A is a trimer composed of
- one alpha chain,
- one beta-A chain
- one beta-B chain
b) hexosaminidase B is a tetramer of
- two beta-A
- two beta-B chains
c) 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
Related
beta-N-acetylhexosaminidase B in fibroblasts
beta-N-acetylhexosaminidase B in leukocytes
beta-N-acetylhexosaminidase B measurement
Sandhoff disease
General
glycoprotein
protein subunit
Properties
SIZE: entity length = 556 aa
MW = 63 kD
COMPARTMENT: lysosome
MOTIF: signal sequence {1-42}
cysteine residue {C91}
MODIFICATION: cysteine residue {C137}
cysteine residue {C137}
MODIFICATION: cysteine residue {C91}
N-glycosylation site {N142}
N-glycosylation site {N190}
cysteine residue {C309}
MODIFICATION: cysteine residue {C360}
N-glycosylation site {N327}
glutamate residue {E355}
cysteine residue {C360}
MODIFICATION: cysteine residue {C309}
cysteine residue {C534}
MODIFICATION: cysteine residue {C551}
cysteine residue {C551}
MODIFICATION: cysteine residue {C534}
Database Correlations
OMIM correlations
MORBIDMAP 606873
UniProt P07686
ENZYME 3.2.1.52
References
- UniProt :accession P07686
- HEXBdb; HEXB mutation database
http://www.hexdb.mcgill.ca/?Topic=HEXBdb
- Name=GeneReviews
https://www.genecards.org/cgi-bin/carddisp.pl?gene=HEXB
Component-of
beta N-acetylhexosaminidase