Glycoside Hydrolase Family 114

• Author: ^^^Spencer Williams^^^
• Responsible Curator: ^^^Spencer Williams^^^

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Glycoside Hydrolase Family GH114
Clan	none
Mechanism	retaining
Active site residues	not known
CAZy DB link
http://www.cazy.org/GH114.html

Substrate specificities

Only a single enzyme of glycoside hydrolase family 114 has been characterized; an endo-α-1,4-polygalactosaminidase from Pseudomonas sp. 881 [1]. 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, and is produced by fungi including Aspergillus parasiticus [2] and Paecilomyces sp. I-1 [3]. An endogalactosaminidase has been purified from Streptomyces griseus; the sequence of this protein is unknown [4].

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 [5]. Tetraose and longer galactosamine oligosaccharides are hydrolyzed to galactosaminobiose and galactosaminotriose as the final products [6]. Based on the dependence of rate on the chain length of the substrate, it was proposed that the enzyme has 8 subsites [6]. The enzyme is inhibited by metal ions including Hg²⁺, Fe²⁺ and Sn²⁺ [5]. Digest of galactosaminotetraose resulted in the transient formation of galactosaminohexaose through a transglycosylation reaction [6]. This supports the assignment of a retaining mechanism to this enzyme and family, and would be consistent with the enzyme utilizing a classical Koshland double-displacement mechanism.

Catalytic Residues

None known.

Three-dimensional structures

No 3-D structure has been reported for any member of this family.

Family Firsts

First stereochemistry determination

A retaining mechanism may be inferred from report of transglycosylation activity [6].

First catalytic nucleophile identification

Not known.

First general acid/base residue identification

Not known.

First 3-D structure

None reported.

References

1. 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. [1].

2. DISTLER JJ and ROSEMAN S. (1960). Galactosamine polymers produced by Aspergillus parasiticus. J Biol Chem. 1960;235:2538-41. | Google Books | Open Library

3. Takagi, H., Kadowaki, K. Purification and Chemical Properties of a Flocculant Produced by Paecilomyces. Agric. Biol. Chem. 1985, 49, 3159-3164. [1]

4. Reissig JL, Lai WH, and Glasgow JE. (1975). An endogalactosaminidase from Streptomyces griseus. Can J Biochem. 1975;53(12):1237-49. DOI:10.1139/o75-169 |

5. 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. [1].

6. Tamura J, Abe T, Hasegawa K, and Kadowaki K. (1992). The Mode of Action of Endo α-1,4 Polygalactosaminidase from Pseudomonas sp. 881 on Galactosaminooligosaccharides. Biosci Biotechnol Biochem. 1992;56(3):380-3. DOI:10.1271/bbb.56.380 |