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

    Normal   0               false   false   false      EN-US   X-NONE   X-NONE                                                     MicrosoftInternetExplorer4

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].

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].

Catalytic Residues

Exploiting the transglycosylation capabilities of Endo-M from M. hiemalis, three residues were identified by site directed mutagenesis to be central to the catalytic reaction: N175, E177, and Y217 [10]. Mutation of the tyrosine to phenylalanine diminished hydrolytic capability but enhanced transglycosylation. The role of N175 was demonstrated to be fundamental for hydrolysis as substitution with alanine ablated hydrolysis; however, transglycosylation could be performed using oxazoline substrates. Interactions between homologous asparagines residues in Endo-A (N171) and Endo-D (N335) were confirmed by structural studies, which observed each in contact with the 2-acetamido group in contact with NAG-thiazoline inhibitors [5, 11]. E177 operates as the catalytic acid and donates a protein to the glycosidic oxygen [10], a role first suggested following the mutagenesis of E174 in Endo-H from Streptomyces plicatus [12].

Family Firsts

First stereochemistry determination: ¹H NMR spectroscopy was used on the products of 3-fluoro-4-nitrophenyl 2-acetamido-2-deoxy-beta-D-glucopyranoside cleavage by Endo-D from S. pneumoniae TIGR4 (SpGH85) [5].

First catalytic nucleophile identification: the 2-acetamido group acting as a nucleophile was suggested by [13] following transglycosylation of a disaccharide oxazoline substrate.

First general acid/base residue identification: catalytic acid was identified by the site-directed mutagenesis of E174 in Endo-H [12]. The “catalytic base” that deprotonates the 2-acetamido group was identified by the site-directed mutagenesis of N175 in Endo-M [10].

First 3-D structure: S. pneumoniae R6 Endo-D PDB ID: 3GBD (release date: 2009-03-17). Unpublished.

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, Macauley MS, Vocadlo DJ, and Boraston AB. (2009). Streptococcus pneumoniae endohexosaminidase D, structural and mechanistic insight into substrate-assisted catalysis in family 85 glycoside hydrolases. J Biol Chem. 2009;284(17):11676-89. DOI:10.1074/jbc.M809663200 |
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 |
10. Umekawa M, Huang W, Li B, Fujita K, Ashida H, Wang LX, and Yamamoto K. (2008). Mutants of Mucor hiemalis endo-beta-N-acetylglucosaminidase show enhanced transglycosylation and glycosynthase-like activities. J Biol Chem. 2008;283(8):4469-79. DOI:10.1074/jbc.M707137200 |
11. Yin J, Li L, Shaw N, Li Y, Song JK, Zhang W, Xia C, Zhang R, Joachimiak A, Zhang HC, Wang LX, Liu ZJ, and Wang P. (2009). Structural basis and catalytic mechanism for the dual functional endo-beta-N-acetylglucosaminidase A. PLoS One. 2009;4(3):e4658. DOI:10.1371/journal.pone.0004658 |
12. Schmidt BF, Ashizawa E, Jarnagin AS, Lynn S, Noto G, Woodhouse L, Estell DA, and Lad P. (1994). Identification of two aspartates and a glutamate essential for the activity of endo-beta-N-acetylglucosaminidase H from Streptomyces plicatus. Arch Biochem Biophys. 1994;311(2):350-3. DOI:10.1006/abbi.1994.1247 |
13. Fujita M, Shoda S, Haneda K, Inazu T, Takegawa K, and Yamamoto K. (2001). A novel disaccharide substrate having 1,2-oxazoline moiety for detection of transglycosylating activity of endoglycosidases. Biochim Biophys Acta. 2001;1528(1):9-14. DOI:10.1016/s0304-4165(01)00164-7 |
14. Ling Z, Suits MD, Bingham RJ, Bruce NC, Davies GJ, Fairbanks AJ, Moir JW, and Taylor EJ. (2009). The X-ray crystal structure of an Arthrobacter protophormiae endo-beta-N-acetylglucosaminidase reveals a (beta/alpha)(8) catalytic domain, two ancillary domains and active site residues key for transglycosylation activity. J Mol Biol. 2009;389(1):1-9. DOI:10.1016/j.jmb.2009.03.050 |

[[Category:Glycoside Hydrolase Families|GH85]]