Hexosaminidases
| Hexosaminidases | ||
|---|---|---|
| Identifier | ||
| Gene name (s) | HEXA , HEXB , MGEA5 , HEXDC | |
| Enzyme classification | ||
| EC, category | 3.2.1.52 , glycosidase | |
| Response type | Hydrolysis of the terminal O-glycosidic bond in N-acetylglucosides and -galactosides | |
| Substrate | R-GlcNAc-OR '+ H 2 O | |
| Products | R-GlcNAc + R'-OH | |
| Occurrence | ||
| Parent taxon | Eukaryotes , bacteria | |
Hexosaminidases are enzymes that split off terminal residues of N-acetylglucosides by hydrolysis and break them down step by step. This reaction is part of the breakdown of glycosaminoglycans and glycosphingolipids in animals and of chitin in plants and bacteria . Five proteins with hexosaminidase activity are known to exist in humans, which occur in several isoforms and assemble to form enzyme complexes . Mutations in the HEXA - gene are the cause of Tay-Sachs disease and mutations at HEXB gene are for Sandhoff disease responsible.
The five hexosaminidases are named hexosaminidases A through D and S. Hexosaminidase A, B and S are protein complexes and are both formed from products of the two genes HEXA (subunit α) and HEXB (subunit βA and βB). The A enzyme is a trimer α-βA-βB, the B enzyme is a tetramer βA-βA-βB-βB, and the S enzyme is a dimer α-α. Finally, hexosaminidase C is the monomer of the MGEA5 gene product and D is the dimer of the HEXDC gene product.
Hexosaminidases form family 20 in the Henrissat classification of glycosidases.