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Difference between revisions of "Glycoside Hydrolase Family 93"
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== Kinetics and Mechanism == | == 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'' <cite>3</cite>. This proposal obtained recent support from the crystal structure of the Arb93A enzyme from ''Fusarium graminearum'' in complex with arabinobiose, the degradation product of | + | 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'' <cite>3</cite>. This proposal obtained recent support from the crystal structure of the Arb93A enzyme from ''Fusarium graminearum'' in complex with arabinobiose, the degradation product of methyl α-arabinotetraose. <cite>2</cite> |
== Catalytic Residues == | == Catalytic Residues == | ||
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== Three-dimensional structures == | == Three-dimensional structures == | ||
| − | The crystal structure of Arb93A reveals a six-bladed beta-propeller fold characteristic of sialidases of clan | + | The crystal structure of Arb93A reveals a six-bladed β-propeller fold characteristic of sialidases of [[clan]] GH-E. <cite>2</cite>, <cite>4</cite> The catalytic machinery is however very different from that of sialidases. |
[[Image:Overalla4.jpg|Arb93A]] | [[Image:Overalla4.jpg|Arb93A]] | ||
Revision as of 17:53, 8 June 2011
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| 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 glycoside hydrolases of family GH93 are known to hydrolyse linear α-1,5-L-arabinan. [1], [2], EC:3.2.1-.
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 [3]. This proposal obtained recent support from the crystal structure of the Arb93A enzyme from Fusarium graminearum in complex with arabinobiose, the degradation product of methyl α-arabinotetraose. [2]
Catalytic Residues
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. [2]
Three-dimensional structures
The crystal structure of Arb93A reveals a six-bladed β-propeller fold characteristic of sialidases of clan GH-E. [2], [4] The catalytic machinery is however very different from that of sialidases.
Family Firsts
First sterochemistry determination
This was determined with the Penicillium chrysogenum Abxn enzyme using 1H-NMR to identify the transglycosylation products [3]
First catalytic nucleophile identification This was proposed based on the structure of Fusarium graminearum Arb93A [2]
First general acid/base residue identification This was proposed based on the structure of Fusarium graminearum Arb93A [2]
First 3-D structure Determined for Fusarium graminearum Arb93A by Carapito and co-workers [2]
References
- Sakamoto T and Thibault JF. (2001). Exo-arabinanase of Penicillium chrysogenum able to release arabinobiose from alpha-1,5-L-arabinan. Appl Environ Microbiol. 2001;67(7):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. 2009;284(18):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. 2004;1674(1):85-90. DOI:10.1016/j.bbagen.2004.06.001 |
- 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. 1995;3(11):1197-205. DOI:10.1016/s0969-2126(01)00255-6 |