Glycoside Hydrolase Family 46

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• Author: ^^^Ryszard Brzezinski^^^
• Responsible Curator: ^^^Ryszard Brzezinski^^^

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Glycoside Hydrolase Family GHnn
Clan	GH-I
Mechanism	inverting
Active site residues	known
CAZy DB link
http://www.cazy.org/fam/GH46.html

Substrate specificities

Glycoside hydrolases of family 46 are essentially endo-beta-1,4-chitosanases (EC 3.2.1.132)that hydrolyze various links in chitosan, a polymer of beta-1,4-linked D-glucosamine (GlcN) units with a variable content (mostly 0 - 35%) of N-acetyl-D-glucosamine (GlcNAc)[1], [2]. Among the four types of links occurring between these two kinds of subunits, all the enzymes examined for their cleavage specificity recognized productively the GlcN-GlcN links. Furthermore, the chitosanase from Bacillus circulans MH-KI recognizes also GlcN-GlcNAc links, while the chitosanase from Streptomyces sp. N174 recognizes the GlcNAc-GlcN links.

Kinetics and Mechanism

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Catalytic Residues

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Three-dimensional structures

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Family Firsts

First sterochemistry determination

Cite some reference here, with a short (1-2 sentence) explanation [3].

First catalytic nucleophile identification

Cite some reference here, with a short (1-2 sentence) explanation [4].

First general acid/base residue identification

Cite some reference here, with a short (1-2 sentence) explanation [5].

First 3-D structure

Cite some reference here, with a short (1-2 sentence) explanation [6].

References

3. Comfort DA, Bobrov KS, Ivanen DR, Shabalin KA, Harris JM, Kulminskaya AA, Brumer H, and Kelly RM. (2007). Biochemical analysis of Thermotoga maritima GH36 alpha-galactosidase (TmGalA) confirms the mechanistic commonality of clan GH-D glycoside hydrolases. Biochemistry. 2007;46(11):3319-30. DOI:10.1021/bi061521n |

4. Sinnott, M.L. (1990) Catalytic mechanisms of enzymic glycosyl transfer. Chem. Rev. 90, 1171-1202. DOI: 10.1021/cr00105a006

5. He S and Withers SG. (1997). Assignment of sweet almond beta-glucosidase as a family 1 glycosidase and identification of its active site nucleophile. J Biol Chem. 1997;272(40):24864-7. DOI:10.1074/jbc.272.40.24864 |