| Symbol: | Melibiase |
| Melibiase | |
| Pfam: | PF02065 |
| Pfam Clan: | CL0058 |
| Interpro: | IPR000111 |
| Scop: | 1ktc |
| Cazy: | GH36 |
| Symbol: | Raffinose_syn |
| Raffinose_syn | |
| Pfam: | PF05691 |
| Pfam Clan: | CL0058 |
| Interpro: | IPR008811 |
| Cazy: | GH36 |
In molecular biology, glycoside hydrolase family 36 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 36 together with family 31 and family 27 alpha-galactosidases form the glycosyl hydrolase clan GH-D, a superfamily of alpha-galactosidases, alpha-N-acetylgalactosaminidases, and isomaltodextranases which are likely to share a common catalytic mechanism and structural topology.
Alpha-galactosidase (melibiase)[8] catalyzes the hydrolysis of melibiose into galactose and glucose. In man, the deficiency of this enzyme is the cause of Fabry's disease (X-linked sphingolipidosis). Alpha-galactosidase is present in a variety of organisms. There is a considerable degree of similarity in the sequence of alpha-galactosidase from various eukaryotic species. Escherichia coli alpha-galactosidase (gene melA), which requires NAD and magnesium as cofactors, is not structurally related to the eukaryotic enzymes; by contrast, an Escherichia coli plasmid encoded alpha-galactosidase (gene rafA)[9] contains a region of about 50 amino acids which is similar to a domain of the eukaryotic alpha-galactosidases. Alpha-N-acetylgalactosaminidase [10] catalyzes the hydrolysis of terminal non-reducing N-acetyl-D-galactosamine residues in N-acetyl-alpha-D- galactosaminides. In man, the deficiency of this enzyme is the cause of Schindler and Kanzaki diseases. The sequence of this enzyme is highly related to that of the eukaryotic alpha-galactosidases.
This family also includes raffinose synthase proteins, also known as seed inhibition (Sip1) proteins. Raffinose (O-alpha- D-galactopyranosyl- (1-->6)- O-alpha- D-glucopyranosyl-(1<-->2)- O-beta- D-fructofuranoside) is a widespread oligosaccharide in plant seeds and other tissues. Raffinose synthase is the key enzyme that channels sucrose into the raffinose oligosaccharide pathway.[11]
Glycoside hydrolase family 36 also includes enzymes with α-N-acetylgalactosaminidase and stachyose synthase activities.
Glycoside hydrolase family 36 can be subdivided into 11 families, GH36A to GH36K.[12]