Reaction: HEXB cleaves the terminal GalNAc from keratan sulfate
- in pathway: Keratan sulfate degradation
Beta-hexosaminidase (HEX) cleaves the terminal N-acetyl galactosamine (GalNAc) from glucosaminoglycans (GAGs) and any other molecules containing a terminal GalNAc. There are two forms of HEX: HEXA and B. The A form is a trimer of the subunits alpha, beta A and beta B. The B form is a tetramer of 2 beta A and 2 beta B subunits (O'Dowd et al. 1988). Defects in the two subunits cause lysosomal storage diseases marked by the accumulation of GM2 gangliosides in neuronal cells.
Reaction - small molecule participants:
Gal-GlcNAc(S)-Gal [lysosomal lumen]
GalNAc [lysosomal lumen]
H2O [lysosomal lumen]
GlcNAc-Gal-GlcNAc(S)-Gal [lysosomal lumen]
Reactome.org reaction link: R-HSA-9638078
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Reaction input - small molecules:
water
beta-D-GlcpNAc-(1->3)-beta-D-Galp-(1->4)-beta-D-GlcpNAc6S-(1->3)-D-Galp
Reaction output - small molecules:
beta-D-Galp-(1->4)-beta-D-GlcpNAc6S-(1->3)-D-Galp
N-acetyl-D-galactosamine
Reactome.org link: R-HSA-9638078