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Glycoside Hydrolase Family 93
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|Glycoside Hydrolase Family GH93|
|Active site residues||known|
|CAZy DB link|
Kinetics and Mechanism
GH93 enzymes are exo-acting enzymes that only release arabinobiose from the non-reducing end of α-1,5-L-arabinan. These enzymes are proposed to be retaining enzymes based on the 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 . This proposal obtained support from the crystal structures of the Arb93A enzyme from Fusarium graminearum and Abnx both in complex with arabinobiose [2, 4]. α-L-Arabinofuranosylated pyrrolidines were shown to be good inhibitors of Arb93A. The Arb93A complex structure with a deoxyiminosugar equivalent of arabinobiose revealed a 4TN twist conformation expected for the Michaelis complex, as seen for several retaining GH51 α-L-arabinofuranosidases. 
From the crystal structure of Arb93A, Glu170 and Glu242 are proposed to act as catalytic nucleophile and general acid/base respectively. Mutagenesis experiment support their role in catalysis and they are strictly conserved among the family members.  Recent structures and mutagenesis studies for the arabinanase Abnx from Penicillium chrysogenum 31B strengthened this assignment. Mutations to alanine or glutamine of their equivalent Glu174 and Glu246 lead to inactive enzyme. 
First sterochemistry determination
This was determined with the Penicillium chrysogenum Abxn enzyme using 1H-NMR to identify the transglycosylation products 
First 3-D structure Determined for Fusarium graminearum Arb93A by Carapito and co-workers 
- Sakamoto T and Thibault JF. (2001) Exo-arabinanase of Penicillium chrysogenum able to release arabinobiose from alpha-1,5-L-arabinan. Appl Environ Microbiol. 67, 3319-21. DOI:10.1128/AEM.67.7.3319-3321.2001 |
- Carapito R, Imberty A, Jeltsch JM, Byrns SC, Tam PH, Lowary TL, Varrot A, and Phalip V. (2009) Molecular basis of arabinobio-hydrolase activity in phytopathogenic fungi: crystal structure and catalytic mechanism of Fusarium graminearum GH93 exo-alpha-L-arabinanase. J Biol Chem. 284, 12285-96. DOI:10.1074/jbc.M900439200 |
- Sakamoto T, Fujita T, and Kawasaki H. (2004) Transglycosylation catalyzed by a Penicillium chrysogenum exo-1,5-alpha-L-arabinanase. Biochim Biophys Acta. 1674, 85-90. DOI:10.1016/j.bbagen.2004.06.001 |
- Sogabe Y, Kitatani T, Yamaguchi A, Kinoshita T, Adachi H, Takano K, Inoue T, Mori Y, Matsumura H, Sakamoto T, and Tada T. (2011) High-resolution structure of exo-arabinanase from Penicillium chrysogenum. Acta Crystallogr D Biol Crystallogr. 67, 415-22. DOI:10.1107/S0907444911006299 |
- Goddard-Borger ED, Carapito R, Jeltsch JM, Phalip V, Stick RV, Varrot A. α-L-Arabinofuranosylated pyrrolidines as arabinanase inhibitors. Chem Commun 2011 Sep 14;47(34):9684-9686.
- Gaskell A, Crennell S, and Taylor G. (1995) The three domains of a bacterial sialidase: a beta-propeller, an immunoglobulin module and a galactose-binding jelly-roll. Structure. 3, 1197-205.