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Glycoside Hydrolase Family 114
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|Glycoside Hydrolase Family GH114|
|Active site residues||not known|
|CAZy DB link|
Only a single enzyme of glycoside hydrolase family 114 has been characterized; an endo-α-1,4-polygalactosaminidase from Pseudomonas sp. 881 . This enzyme hydrolyzes α-1,4-polygalactosamine to oligosaccharides in an endo-acting manner. α-1,4-Polygalactosamine, also known as galactosaminoglycan, is a polymer consisting of α-1,4-linked galactosamine residues, which is only partially N-acetylated, and may also contain N-formyl residues. The polysaccharide is biosynthesized by fungi including Aspergillus parasiticus  and Paecilomyces sp. I-1 . An endogalactosaminidase has been purified from Streptomyces griseus; the sequence of this protein is unknown .
Kinetics and Mechanism
The endo-α-1,4-polygalactosaminidase from Pseudomonas sp. 881 possesses activity on deacetylated α-1,4-polygalactosamine, but has no activity on fully N-acetylated α-1,4-polygalactosamine . Tetraose and longer galactosamine oligosaccharides are hydrolyzed to galactosaminobiose and galactosaminotriose as the final products . Based on the dependence of rate on the chain length of the substrate, it was proposed that the enzyme has 8 subsites . The enzyme is inhibited by metal ions including Hg2+, Fe2+ and Sn2+ . Digest of galactosaminotetraose resulted in the transient formation of galactosaminohexaose through a transglycosylation reaction . This supports the assignment of a retaining mechanism to this enzyme and family, and is consistent with the enzyme utilizing a classical Koshland double-displacement mechanism.
No 3-D structure has been reported for any member of this family.
- First stereochemistry determination
- A retaining mechanism may be inferred from report of transglycosylation activity .
- First catalytic nucleophile identification
- Not known.
- First general acid/base residue identification
- Not known.
- First 3-D structure
- None reported.
- Tamura, J.-I., Hasegawa, K., Kadowaki, K., Igarashi, Y., Kodama, T. Molecular Cloning and Sequence Analysis of the Gene Encoding an Endo a-l,4 Polygalactosaminidase of Pseudomonas sp. 881. J. Fermentation Bioengineer., 1995, 80, 305. DOI: 10.1016/0922-338X(95)94196-X.
- DISTLER JJ and ROSEMAN S. Galactosamine polymers produced by Aspergillus parasiticus. J Biol Chem. 1960 Sep;235:2538-41.
- Takagi, H., Kadowaki, K. Purification and Chemical Properties of a Flocculant Produced by Paecilomyces. Agric. Biol. Chem. 1985, 49, 3159-3164. DOI: 10.1080/00021369.1985.10867250
- Reissig JL, Lai WH, and Glasgow JE. An endogalactosaminidase from Streptomyces griseus. Can J Biochem. 1975 Dec;53(12):1237-49.
- Tamura, J.-I., Takagi, H., Kadowaki, K. Purification and Some Properties of the Endo α-1,4 Polygalactosaminidase from Pseudomonas sp., Agric. Biol. Chem. 1988, 52, 2475-2484. DOI: 10.1080/00021369.1988.10869068.
- Tamura J, Abe T, Hasegawa K, and Kadowaki K. The Mode of Action of Endo α-1,4 Polygalactosaminidase from Pseudomonas sp. 881 on Galactosaminooligosaccharides. Biosci Biotechnol Biochem. 1992 Jan;56(3):380-3. DOI:10.1271/bbb.56.380 |