PROSITE documentation PDOC00507

Glycosyl hydrolases family 17 signature

It has been shown [1,2] that the following glycosyl hydrolases can be classified into a single family on the basis of sequence similarities:

• Glucan endo-1,3-β-D-glucosidases (EC 3.2.1.39) (endo-(1->3)-β- glucanase) from various plants. This enzyme may be involved in the defense of plants against pathogens through its ability to degrade fungal cell wall polysaccharides.
• Glucan 1,3-β-glucosidase (EC 3.2.1.58) (exo-(1->3)-β-glucanase) from yeast (gene BGL2). This enzyme may play a role in cell expansion during growth, in cell-cell fusion during mating, and in spore release during sporulation.
• Lichenases (EC 3.2.1.73) (endo-(1->3,1->4)-β-glucanase) from various plants.

The best conserved region in the sequence of these enzymes is located in their central section. This region contains a conserved tryptophan residue which could be involved in the interaction with the glucan substrates [2] and it also contains a conserved glutamate which has been shown [3] to act as the nucleophile in the catalytic mechanism. We have used this region as a signature pattern.