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Glycoside Hydrolase Family 93
- Author: Annabelle Varrot
- Responsible Curator: Annabelle Varrot
| Glycoside Hydrolase Family GH93 | |
| Clan | GH-E |
| Mechanism | retaining |
| Active site residues | known |
| CAZy DB link | |
| http://www.cazy.org/fam/GH93.html | |
Substrate specificities
The characterized member of family 93 are known to hydrolyse α-1,5-L-arabinan. EC:3.2.1-
Kinetics and Mechanism
GH93 enzymes are exoenzymes which only release arabinobiose from the non-reducing end. Net retention of the configuration of the anomeric carbon is proposed from the products of the transglycosylation activity of the protein Abnx from Penicillium chrysogenum. It was recently supported in the crystal structure of the Arb93A enzyme from Fusarium graminearum in complex with arabinobiose.
Catalytic Residues
From the crystal structure of Arb93A, Glu170 and Glu242 are proposed to act as nucleophile and acid/base respectively. Mutagenesis experiment support their role in catalysis and they are strictly conserved between the family members.
Three-dimensional structures
The recent crystal structure of Arb93A reveals a six-bladed beta-propeller fold characteristic of sialidases of clan GHE. The catalytic machinery is however very different from that of sialidases.