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Difference between revisions of "Glycoside Hydrolase Family 135"
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== Substrate specificities == | == Substrate specificities == | ||
A single report has disclosed fungal [[glycoside hydrolases]] with the ability to degrade a fungal heteropolysaccharide galactosaminogalactan (GAG) <cite>Bamford2015</cite>. GAG is produced by ''Aspergillus fumigatus'' as an exopolysaccharide, which is α-1,4-linked galactose, ''N''-acetylgalactosamine, and galactosamine residues, and which is found in both a secreted form and bound to the cell wall of hyphae. The recombinant protein | A single report has disclosed fungal [[glycoside hydrolases]] with the ability to degrade a fungal heteropolysaccharide galactosaminogalactan (GAG) <cite>Bamford2015</cite>. GAG is produced by ''Aspergillus fumigatus'' as an exopolysaccharide, which is α-1,4-linked galactose, ''N''-acetylgalactosamine, and galactosamine residues, and which is found in both a secreted form and bound to the cell wall of hyphae. The recombinant protein | ||
| − | purified and cell wall-associated GAG. While it is unclear precisely where within the GAG chain the enzyme acts, and thus whether it should be considered an α-galactosidase, α-galactosaminase or an α-galactosaminidase, and 3-D complex of the protein with ''N''-acetylgalactosamine (see below) is suggestive that the enzyme possesses α-galactosaminidase activity. | + | purified and cell wall-associated GAG. While it is unclear precisely where within the GAG chain the enzyme acts, and thus whether it should be considered an α-galactosidase, α-galactosaminase (i.e. cleaving an α-galactosamine linkage) or an ''N''-acetyl-α-galactosaminidase, and 3-D complex of the protein with ''N''-acetylgalactosamine (see below) is suggestive that the enzyme possesses α-galactosaminidase activity. |
== Kinetics and Mechanism == | == Kinetics and Mechanism == | ||
| − | + | Very little is known about the kinetics or mechanism of this enzyme, owing to the lack of homogeneous, well-defined substrates. No activty was detected using a range of simple 4-nitrophenyl glycosides <cite>Bamford2015</cite>. Instead, the cleavage GAG by Sph3 could be monitored by release of reducing ends. | |
== Catalytic Residues == | == Catalytic Residues == | ||
| − | + | Structural and sequence alignments identified three conserved acidic amino acid residues, Asp166, Glu167, and Glu222, which were located within the putative active site groove. | |
== Three-dimensional structures == | == Three-dimensional structures == | ||
| − | Three-dimensional structures are available for one GH family 135 member, ''Aspergillus clavatus'' Sph3 <cite>Bamford2015</cite>. This protein has a classical (β/α)<sub>8</sub> TIM barrel fold.with | + | Three-dimensional structures are available for one GH family 135 member, ''Aspergillus clavatus'' Sph3 <cite>Bamford2015</cite>. This protein has a classical (β/α)<sub>8</sub> TIM barrel fold. THis foad was described as sharing similarities with enzymes belonging to families [[GH18]], [[GH27]], and [[GH84]]. |
| − | |||
| − | |||
== Family Firsts == | == Family Firsts == | ||
Revision as of 22:01, 29 October 2016
This page is currently under construction. This means that the Responsible Curator has deemed that the page's content is not quite up to CAZypedia's standards for full public consumption. All information should be considered to be under revision and may be subject to major changes.
- Author: ^^^Spencer Williams^^^
- Responsible Curator: ^^^Spencer Williams^^^
| Glycoside Hydrolase Family GH135 | |
| Clan | none |
| Mechanism | unknown |
| Active site residues | known/not known |
| CAZy DB link | |
| http://www.cazy.org/GH135.html | |
Substrate specificities
A single report has disclosed fungal glycoside hydrolases with the ability to degrade a fungal heteropolysaccharide galactosaminogalactan (GAG) [1]. GAG is produced by Aspergillus fumigatus as an exopolysaccharide, which is α-1,4-linked galactose, N-acetylgalactosamine, and galactosamine residues, and which is found in both a secreted form and bound to the cell wall of hyphae. The recombinant protein purified and cell wall-associated GAG. While it is unclear precisely where within the GAG chain the enzyme acts, and thus whether it should be considered an α-galactosidase, α-galactosaminase (i.e. cleaving an α-galactosamine linkage) or an N-acetyl-α-galactosaminidase, and 3-D complex of the protein with N-acetylgalactosamine (see below) is suggestive that the enzyme possesses α-galactosaminidase activity.
Kinetics and Mechanism
Very little is known about the kinetics or mechanism of this enzyme, owing to the lack of homogeneous, well-defined substrates. No activty was detected using a range of simple 4-nitrophenyl glycosides [1]. Instead, the cleavage GAG by Sph3 could be monitored by release of reducing ends.
Catalytic Residues
Structural and sequence alignments identified three conserved acidic amino acid residues, Asp166, Glu167, and Glu222, which were located within the putative active site groove.
Three-dimensional structures
Three-dimensional structures are available for one GH family 135 member, Aspergillus clavatus Sph3 [1]. This protein has a classical (β/α)8 TIM barrel fold. THis foad was described as sharing similarities with enzymes belonging to families GH18, GH27, and GH84.
Family Firsts
- First stereochemistry determination
- Unknown.
- First catalytic nucleophile identification
- Unknown.
- First general acid/base residue identification
- Unknown.
- First 3-D structure
- Sph3 from Aspergillus clavatus [1].
References
- Bamford NC, Snarr BD, Gravelat FN, Little DJ, Lee MJ, Zacharias CA, Chabot JC, Geller AM, Baptista SD, Baker P, Robinson H, Howell PL, and Sheppard DC. (2015). Sph3 Is a Glycoside Hydrolase Required for the Biosynthesis of Galactosaminogalactan in Aspergillus fumigatus. J Biol Chem. 2015;290(46):27438-50. DOI:10.1074/jbc.M115.679050 |