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Glycoside Hydrolase Family 75
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|Glycoside Hydrolase Family GH75|
|Active site residues||Inferred|
|CAZy DB link|
Glycoside hydrolases of family 75 include both eukaryotic (essentially fungal) and prokaryotic proteins. They have so far been characterized only from filamentous fungi. They are beta-1,4-chitosanases with endo-splitting activity [1, 2]. The analysis of the final product of hydrolysis of partially N-deacetylated chitosan by the GH75 chitosanase from Aspergillus fumigatus suggests that this enzyme cleaves preferentially GlcN-GlcN and GlcNAc-GlcN links in the polysaccharide chain .
Kinetics and Mechanism
Family GH46 enzymes are classified as inverting enzymes. This has been shown by 1H NMR for the enzyme from Aspergillus fumigatus using chitosan as substrate .
A site-directed mutagenesis study performed on the enzyme from Fusarium solani (expressed as a recombinant protein in Saccharomyces cerevisiae) showed that Asp175 and Glu188 are essential for catalysis . This was confirmed by a study on the chitosanase from Aspergillus fumigatus (expressed as a recombinant protein in Escherichia coli) showing that the corresponding residues Asp160 and Glu169 are essential for catalysis . Both residues are strictly conserved among eukaryotic and prokaryotic GH75 family members.
No three-dimensional structure has been solved for this family.
- First primary structure determination
- Chitosanase from Fusarium solani f. sp. phaseoli .
- First stereochemistry determination
- Chitosanase from Aspergillus fumigatus .
- First catalytic nucleophile identification
- Not yet identified.
- First general acid/base residue identification
- Not yet identified.
- First 3-D structure
- Not yet determined.
- Shimosaka M, Nogawa M, Ohno Y, and Okazaki M. Chitosanase from the pathogenic fungus, Fusarium solani f.sp. phaseoli - purification and some properties. Biosci. Biotech. Biochem. 1993 57, 231-235.
- Cheng CY and Li YK. An Aspergillus chitosanase with potential for large-scale preparation of chitosan oligosaccharides. Biotechnol Appl Biochem. 2000 Dec;32 ( Pt 3):197-203.
- Cheng CY, Chang CH, Wu YJ, and Li YK. Exploration of glycosyl hydrolase family 75, a chitosanase from Aspergillus fumigatus. J Biol Chem. 2006 Feb 10;281(6):3137-44. DOI:10.1074/jbc.M512506200 |
- Shimosaka M, Sato K, Nishiwaki N, Miyazawa T, and Okazaki M. Analysis of essential carboxylic amino acid residues for catalytic activity of fungal chitosanases by site-directed mutagenesis. J Biosci Bioeng. 2005 Nov;100(5):545-50. DOI:10.1263/jbb.100.545 |
- Shimosaka M, Kumehara M, Zhang X-Y, Nogawa M, and Okazaki M. Cloning and characterization of a chitosanase gene from the plant pathogenic fungus Fusarium solani. J. Ferment. Bioeng. 1996 82, 426-431.