Glycoside Hydrolase Family 92

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• Author: ^^^Harry Gilbert^^^
• Responsible Curator: ^^^Harry Gilbert^^^

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Glycoside Hydrolase Family GHnn
Clan	GH-x
Mechanism	retaining/inverting
Active site residues	known/not known
CAZy DB link
http://www.cazy.org/fam/GHnn.html

Substrate specificities

GH92 enzymes are exo-acting alpha-mannosidases. The first reported enzyme activity from this family was an alpha1,2-mannosidase from Microbacterium sp. M-90. [1] Recently the characterization of 22 GH92 enzymes from Bacteroides thetaiotaomicron confirmed an exo-mode of action but alpha1,2-mannosidase, alpha1,3-mannosidase, alpha1,4-mannosidase and alpha1,6-mannosidase activities were detected [2] [3, 4, 5].

Kinetics and Mechanism

1H-NMR studies on three GH92s that displayed alpha1,2-, alpha1,3- and alpha1,4-mannosidase activities all generated beta-mannose indicating that these enzymes catalyse glycosidic bond hydrolysis through a single displacement mechanism leading to inversion of anomeric configuration [3, 4, 5].

Catalytic Residues

Content is to be added here. Based on 3D structural data on the alpha1,2-mannosidase Bt3990 Glu533 is the predicted catalytic acid. This view is supported by a mutant of this residue, which is essentially inactive, and its conservation throughout the GH92 family.

Three-dimensional structures

Content is to be added here.

Family Firsts

First sterochemistry determination

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

First catalytic nucleophile identification

Cite some reference here, with a short (1-2 sentence) explanation [7].

First general acid/base residue identification

Cite some reference here, with a short (1-2 sentence) explanation [8].

First 3-D structure

Cite some reference here, with a short (1-2 sentence) explanation [9].

References

6. 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 |

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

8. 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 |
9. Robert V. Stick and Spencer J. Williams. (2009) Carbohydrates. Elsevier Science.