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Glycoside Hydrolase Family 38
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| Glycoside Hydrolase Family GH38 | |
| Clan | GH-x |
| Mechanism | retaining |
| Active site residues | known |
| CAZy DB link | |
| http://www.cazy.org/fam/GH38.html | |
Substrate specificities
GH38 enzymes are Class II α-mannosidases. They range in breadth of specificity from the Golgi α-mannosidase (2A1), which has a dual specificity for α1,6 and α1,3-linked mannoses, to the lysosomal mannosidases, which have either broad (2B1 cleaves α1,2, α1,3 and α1,6 linkages) or narrow specificities (2B2 is specific for α1,6). GH38 active sites can be quite long and open, and some are sensitive to the polysaccharide substrate structure. For example, Golgi α-mannosidase II requires the presence of a GlcNAc residue some five residues away from the cleavage site, while lysosomal mannosidases do not have that requirement.
Kinetics and Mechanism
GH38 enzymes operate by the conventional Koshland double-displacement retaining mechanism. There have been GH38 mannosidases identified in a number of different localizations, classed into subfamilies with different substrate specificities and biochemical properties, and , presumably, different physiological roles. The Golgi enzyme is identified as 2A1 (Class 2, A for Golgi, enzyme 1). Lysosomal GH38 mannosidases are indicated by 'B' (2B1, 2B2) and those likely existing in the cytoplasm by 'C'.
Catalytic Residues
Three-dimensional structures
Family Firsts
- First sterochemistry determination
- Cite some reference here, with a short explanation [1].
- First catalytic nucleophile identification
- First general acid/base residue identification
- First 3-D structure
References
- 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 |
[[Category:Glycoside Hydrolase Families]]