| Symbol: | Glyco_hydro_20 |
| Glycosyl hydrolase family 20, catalytic domain | |
| Pfam: | PF00728 |
| Pfam Clan: | CL0058 |
| Interpro: | IPR015883 |
| Scop: | 1qba |
| Cazy: | GH20 |
| Cdd: | cd02742 |
| Symbol: | Glyco_hydro_20b |
| Glycosyl hydrolase family 20, domain 2 | |
| Pfam: | PF02838 |
| Interpro: | IPR015882 |
| Scop: | 1qba |
| Cazy: | GH20 |
In molecular biology, glycoside hydrolase family 20 is a family of glycoside hydrolases.
Glycoside hydrolases are a widespread group of enzymes that hydrolyse the glycosidic bond between two or more carbohydrates, or between a carbohydrate and a non-carbohydrate moiety. A classification system for glycoside hydrolases, based on sequence similarity, has led to the definition of >100 different families.[1] [2] [3] This classification is available on the CAZy web site,[4] [5] and also discussed at CAZypedia, an online encyclopedia of carbohydrate active enzymes.[6] [7]
Glycoside hydrolase family 20 CAZY GH_20 comprises enzymes with several known activities; beta-hexosaminidase ; lacto-N-biosidase . Carbonyl oxygen of the C-2 acetamido group of the substrate acts as the catalytic nucleophile/base in this family of enzymes.
In the brain and other tissues, beta-hexosaminidase A degrades GM2 gangliosides; specifically, the enzyme hydrolyses terminal non-reducing N-acetyl-D-hexosamine residues in N-acetyl-beta-D-hexosaminides. There are 3 forms of beta-hexosaminidase: hexosaminidase A is a trimer, with one alpha, one beta-A and one beta-B chain; hexosaminidase B is a tetramer of two beta-A and two beta-B chains; and hexosaminidase S is a homodimer of alpha chains. The two beta chains are derived from the cleavage of a precursor. Mutations in the beta-chain lead to Sandhoff disease, a lysosomal storage disorder characterised by accumulation of GM2 ganglioside.[8]