HEXB
HEXB is the beta subunit of the lysosomal enzyme beta-hexosaminidase, a glycosyl hydrolase that removes terminal N-acetyl-D-hexosamine residues from glycoconjugates. It was previously named hexosaminidase B (beta polypeptide), and mutations in the HEXB gene cause Sandhoff disease. Browse Assay Genie's current range of HEXB research reagents below, or read on for the biology behind the target.
HEXB (hexosaminidase subunit beta) encodes the beta subunit of beta-hexosaminidase. The enzyme hydrolyses the non-reducing end N-acetyl-D-hexosamine and/or sulfated N-acetyl-D-hexosamine of glycoconjugates, including the oligosaccharide moieties of proteins and neutral glycolipids, and those of certain mucopolysaccharides. Beta-hexosaminidase is built from two subunits, alpha and beta, which are encoded by separate genes. The isozyme B, which contains the beta subunit, does not hydrolyse every one of these substrates but acts efficiently on neutral oligosaccharides. Only the isozyme A is responsible for degrading GM2 gangliosides in the presence of the cofactor GM2 activator protein (GM2A).
The HEXB protein is found in the lysosome and, in oocytes, in cortical granules, and it belongs to the glycosyl hydrolase 20 family, as does the alpha subunit. During fertilisation it contributes, at least in part, to the zona block to polyspermy. Present in the cortical granules of non-activated oocytes, it is exocytosed during the cortical reaction after oocyte activation and inactivates the sperm galactosyltransferase-binding site, which blocks sperm binding to the zona pellucida.
Mutations in the alpha or beta subunit genes lead to accumulation of GM2 ganglioside in neurons and to neurodegenerative disorders termed the GM2 gangliosidoses. Mutations in the HEXB gene specifically cause Sandhoff disease (GM2-gangliosidosis type II). Alternatively spliced transcript variants encoding different isoforms have been reported. The mouse and rat orthologs are both named Hexb.
HEXB mutations cause Sandhoff disease, making the protein central to studies of GM2 gangliosidosis and neuronal ganglioside accumulation.
Beta-hexosaminidase degrades GM2 ganglioside with GM2 activator protein and removes terminal N-acetyl hexosamines from other glycoconjugates.
Loss of beta-hexosaminidase function leads to GM2 ganglioside build-up in neurons, a feature of the neurodegenerative GM2 gangliosidoses.
HEXB is released from oocyte cortical granules and contributes to the zona block to polyspermy by inactivating the sperm galactosyltransferase-binding site.
HEXB encodes the beta subunit of lysosomal beta-hexosaminidase, which hydrolyses terminal N-acetyl-D-hexosamine residues from glycoconjugates. Together with the alpha subunit and GM2 activator protein it supports degradation of GM2 ganglioside. It also contributes to the block to polyspermy during fertilisation.
Beta-hexosaminidase is composed of alpha and beta subunits encoded by separate genes, both in glycosyl hydrolase family 20. Isozyme B efficiently hydrolyses neutral oligosaccharides, but only isozyme A degrades GM2 gangliosides in the presence of GM2A. HEXB was formerly called hexosaminidase B (beta polypeptide).
Mutations in the HEXB gene cause Sandhoff disease (GM2-gangliosidosis type II), with GM2 ganglioside accumulating in neurons. Orthologs exist in mouse and rat, both named Hexb. Check the datasheet of any product for its validated reactivity.
Other hexosaminidase subunits, GM2 ganglioside pathway partners and lysosomal enzymes with products at Assay Genie.
Gene and protein annotations from HGNC, NCBI Gene and UniProt P07686; product specifications from Assay Genie datasheets.