Glycoside Hydrolase Family 85

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• Author: ^^^Wade Abbott^^^
• Responsible Curator: ^^^Al Boraston^^^

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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

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Substrate specificities

GH85 enzymes, commonly referred to as Endo-beta-N-acetylglucosaminidases (ENGse) cleave the chitobiose core (GlcNAc-beta-1,4-GlcNac) of N-linked glycans. Examples of ENGases have been shown to be active on high-mannose type N-glycans (Endo-H, Endo-A, Endo-Fsp, Endo-F1, and Endo-E), bi- and tri-antennary complex type N-glycans (Endo-F2 and Endo-F3), and both substrates (Endo-M). Although specificity appears to be primarily determined by the oligosaccharide glycone[1], there is evidence that structural features within the carbohydrate-protein aglycone region (GlcNAc-Asn) may also play a role in substrate recognition. GH85s are broadly distributed in nature having been described in bacteria [2, 3, 4, 5], fungi [6], plants [7] and animals [8]. In several cases, including Endo-A from Arthrobacter protophormiae (ApGH85) and Endo-M from Mucor hiemalis (MhGH85), ENGases have been shown to catalyze transglycosylation reactions, making them useful candidates in the bioengineering of glycoproteins [1] and biologic pharmaceuticals [9].

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Kinetics and Mechanism

GH85s were originally proposed to utilize a substrate-assisted mechanism resulting in the retention of anomeric configuration on the basis of transglycosylation reactions that deployed oxazoline substrates as donor sugars [10]. Further support was provided by the three-dimensional structure of Endo-A [11] and Endo-D [5]in complex with thiazoline-based inhibitors. NMR spectroscopy was utilized on Endo-D products to demonstrate anomeric retention on cleavage products [5]. GH85s appear to deploy a rare form of substrate-assisted catalysis as a candidate asparagine, operating in an imidic tautomer form, facilitates a “proton shuttle” that results in acid-base catalysis of the glycosidic bond, a role similar to the catalytic aspartates in family 18 and 56 glycoside hydrolases [5].

References

1. Li B, Song H, Hauser S, and Wang LX. (2006). A highly efficient chemoenzymatic approach toward glycoprotein synthesis. Org Lett. 2006;8(14):3081-4. DOI:10.1021/ol061056m |
2. Karamanos Y, Bourgerie S, Barreaud JP, and Julien R. (1995). Are there biological functions for bacterial endo-N-acetyl-beta-D-glucosaminidases?. Res Microbiol. 1995;146(6):437-43. DOI:10.1016/0923-2508(96)80289-0 |
3. Barreaud JP, Bourgerie S, Julien R, Guespin-Michel JF, and Karamanos Y. (1995). An endo-N-acetyl-beta-D-glucosaminidase, acting on the di-N-acetylchitobiosyl part of N-linked glycans, is secreted during sporulation of Myxococcus xanthus. J Bacteriol. 1995;177(4):916-20. DOI:10.1128/jb.177.4.916-920.1995 |
4. Takegawa K, Fujiwara K, Iwahara S, Yamamoto K, and Tochikura T. (1989). Effect of deglycosylation of N-linked sugar chains on glucose oxidase from Aspergillus niger. Biochem Cell Biol. 1989;67(8):460-4. DOI:10.1139/o89-072 |
5. Abbott DW, Ficko-Blean E, van Bueren AL, Rogowski A, Cartmell A, Coutinho PM, Henrissat B, Gilbert HJ, and Boraston AB. (2009). Analysis of the structural and functional diversity of plant cell wall specific family 6 carbohydrate binding modules. Biochemistry. 2009;48(43):10395-404. DOI:10.1021/bi9013424 |
6. Fujita K, Kobayashi K, Iwamatsu A, Takeuchi M, Kumagai H, and Yamamoto K. (2004). Molecular cloning of Mucor hiemalis endo-beta-N-acetylglucosaminidase and some properties of the recombinant enzyme. Arch Biochem Biophys. 2004;432(1):41-9. DOI:10.1016/j.abb.2004.09.013 |
7. Li SC, Asakawa M, Hirabayashi Y, and Li Y. (1981). Isolation of two endo-beta-N-acetylglucosaminidases from fig latex. Biochim Biophys Acta. 1981;660(2):278-83. DOI:10.1016/0005-2744(81)90171-6 |
8. Ito K, Okada Y, Ishida K, and Minamiura N. (1993). Human salivary endo-beta-N-acetylglucosaminidase HS specific for complex type sugar chains of glycoproteins. J Biol Chem. 1993;268(21):16074-81. | Google Books | Open Library
9. Hamilton SR, Davidson RC, Sethuraman N, Nett JH, Jiang Y, Rios S, Bobrowicz P, Stadheim TA, Li H, Choi BK, Hopkins D, Wischnewski H, Roser J, Mitchell T, Strawbridge RR, Hoopes J, Wildt S, and Gerngross TU. (2006). Humanization of yeast to produce complex terminally sialylated glycoproteins. Science. 2006;313(5792):1441-3. DOI:10.1126/science.1130256 |

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[[Category:Glycoside Hydrolase Families|GHnnn]]