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Syn/anti lateral protonation
This page is currently under construction. This means that the Responsible Curator has deemed that the page's content is not quite up to CAZypedia's standards for full public consumption. All information should be considered to be under revision and may be subject to major changes.
- Author: ^^^Wim Nerinckx^^^
- Responsible Curator: ^^^Spencer Williams^^^
Overview
This page provides a table (and eventually a full lexicon article) on the spatial positioning of the catalytic general acid residue in the active sites of glycoside hydrolases. The table below updates those found in the seminal paper on this concept by Heightman and Vasella [1], and the more recent summary by Nerinckx et al. [2].
Table of syn/anti protonation examples
Note
This table contains only one example per GH-family of a ligand-complexed protein structure where the syn positioning (close to the ring-oxygen of the sugar moiety at subsite -1) or anti positioning (at the opposite side of the ring-oxygen, close to C-2) of the proton donor can be clearly observed; other examples may be available on a family-by-family basis. The reader is thus advised to consult the CAZy database for a current, comprehensive list of CAZyme structures. Where available, the selected examples are Michaelis-type complexes with the ligand spanning the -1/+1 subsites, since these have an intact glycosidic or thioglycosidic bond, or are N-analogs of the substrate (e.g. acarbose). In some examples, the proton donor has been mutated (e.g., to the corresponding amide or to an alanine), and in those cases one may wish to look at a superposition of the given PDB example with the structure of the native enzyme. If a Michaelis-type complex is not yet available, the second and third example choices, respectively, are trapped glycosyl-enzyme intermediates and product complexes with the subsite -1 correctly occupied.
Please also be aware that this is a large table with many data, so some (hopefully few) errors may have sneaked in. Please contact the page Author or Responsible Curator with corrections.
Table
This table can be re-sorted by clicking on the icons in the header (javascript must be turned on in your browser). To reset the page to be sorted by GH family, click the page tab at the very top of the page.
| Family | Clan | Structure fold | Anomeric specificity | Mechanism | Syn/anti protonator | Example PDB ID | Enzyme | Organism | Ligand | General acid | Nucleophile or General base | Reference |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| GH1 | A | (β/α)8 | beta | retaining | anti | 2cer | β-glycosidase S | Sulfolobus solfataricus P2 | phenethyl glucoimidazol | Glu206 | Glu387 | [3] |
| GH2 | A | (β/α)8 | beta | retaining | anti | 2vzu | exo-β-glucosaminidase | Amicolatopsis orientalis | PNP-β-d-glucosamine | Glu469 | Glu541 | [4] |
| GH3 | none | (β/α)8 | beta | retaining | anti | 1iex | exo-1,3-1,4-glucanase | Hordeum vulgare | thiocellobiose | Glu491 | Asp285 | [5] |
| GH5 | A | (β/α)8 | beta | retaining | anti | 1h2j | endo-β-1,4-glucanase | Bacillus agaradhaerens | 2',4'-DNP-2-F-cellobioside | Glu129 | Glu228 | [6] |
| GH6 | none | (β/α)8 | beta | inverting | syn | 1qjw | cellobiohydrolase 2 | Hypocrea jecorina | (Glc)2-S-(Glc)2 | Asp221 | debated | [7] |
| GH7 | B | β-jelly roll | beta | retaining | syn | 1ovw | endo-1,4-glucanase | Fusarium oxysporum | thio-(Glc)5 | Glu202 | Glu197 | [8] |
| GH8 | M | (α/α)6 | beta | inverting | anti | 1kwf | endo-1,4-glucanase | Clostridium thermocellum | cellopentaose | Glu95 | Asp278 | [9] |
| GH9 | none | (α/α)6 | beta | inverting | syn | 1rq5 | cellobiohydrolase | Clostridium thermocellum | cellotetraose | Glu795 | Asp383 | [10] |
| GH10 | A | (β/α)8 | beta | retaining | anti | 2d24 | β-1,4-xylanase | Streptomyces olivaceoviridis E-86 | xylopentaose | Glu128 | Glu236 | [11] |
| GH11 | C | β-jelly roll | beta | retaining | syn | 1bvv | xylanase | Bacillus circulans | Xyl-2-F-xylosyl | Glu172 | Glu78 | [12] |
| GH12 | C | β-jelly roll | beta | retaining | syn | 1w2u | endoglucanase | Humicola grisea | thiocellotetraose | Glu205 | Glu120 | [13] |
| GH13 | H | (β/α)8 | alpha | retaining | anti | 1cxk | β-cyclodextrin glucanotransferase | Bacillus circulans | maltononaose | Glu257 | Asp229 | [14] |
| GH14 | none | (β/α)8 | alpha | inverting | syn | 1itc | β-amylase | Bacillus cereus | maltopentaose | Glu172 | Glu367 | [15] |
| GH15 | L | (α/α)6 | alpha | inverting | syn | 1gah | glucoamylase | Aspergillus awamori | acarbose | Glu179 | Glu400 | [16] |
| GH16 | B | β-jelly roll | beta | retaining | syn | 1urx | β-agarase A | Zobellia galactanivorans | oligoagarose | Glu152 | Glu147 | [17] |
| GH17 | A | (β/α)8 | beta | retaining | predicted anti by clan | see e.g. at GH1 | ||||||
| GH18 | K | (β/α)8 | beta | retaining | anti | 1ffr | chitinase A | Serratia marcescens | (NAG)6 | Glu315 | internal | [18] |
| GH20 | K | (β/α)8 | beta | retaining | anti | 1c7s | chitobiase | Serratia marcescens | chitobiose | Glu540 | internal | [19] |
| GH22 | none | lysozyme type | beta | retaining | syn | 1h6m | lysozyme C | Gallus gallus | Chit-2-F-chitosyl | Glu35 | Asp52 | [20] |
| GH23 | none | lysozyme type | beta | inverting | syn | 1lsp | lysozyme G | Cygnus atratus | Bulgecin A | Glu73 | internal | [21] |
| GH24 | I | α + β | beta | inverting | syn | 148l | lysozyme E | Bacteriophage T4 | chitobiosyl | Glu11 | Glu26 | [22] |
| GH26 | A | (β/α)8 | beta | retaining | anti | 1gw1 | mannanase A | Cellvibrio japonicus | 2',4'-DNP-2-F-cellotrioside | Glu212 | Glu320 | [23] |
| GH27 | D | (β/α)8 | alpha | retaining | anti | 1ktc | α-N-acetyl galactosaminidase | Gallus gallus | NAGal | Asp201 | Asp410 | [24] |
| GH28 | N | β-helix | alpha | inverting | anti | 2uvf | exo-polygalacturonosidase | Yersinia enterocolitica ATCC9610D | digalacturonic acid | Asp402 | Asp381 Asp403 | [25] |
| GH29 | none | (β/α)8 | alpha | retaining | syn | 1hl9 | α-l-fucosidase | Thermotoga maritima | 2-F-fuco- pyranosyl | Glu266 | Asp224 | [26] |
| GH30 | A | (β/α)8 | beta | retaining | anti | 2v3d | glucocerebrosidase 1 | Homo sapiens | N-butyl-deoxynojirimycin | Glu235 | Glu340 | [27] |
| GH31 | D | (β/α)8 | alpha | retaining | anti | 2qmj | maltase-glucoamylase | Homo sapiens | acarbose | Asp542 | Asp443 | [28] |
| GH32 | J | 5-fold β-propeller | beta | retaining | anti | 2add | fructan β-(2,1)-fructosidase | Cichorium intybus | sucrose | Glu201 | Asp22 | [29] |
| GH33 | E | 6-fold β-propeller | alpha | retaining | anti | 1s0i | trans-sialidase | Trypanosoma cruzi | sialyl-lactose | Asp59 | Tyr342 | [30] |
| GH34 | E | 6-fold β-propeller | alpha | retaining | anti | 2bat | neuraminidase | Influenza A virus | sialic acid | Asp151 | Tyr406 | [31] |
| GH35 | A | (β/α)8 | beta | retaining | anti | 1xc6 | β-galactosidase | Penicillium sp. | d-galactose | Glu200 | Glu299 | [32] |
| GH37 | G | (α/α)6 | alpha | inverting | anti | 2jf4 | trehalase | Escherechia coli | validoxylamine | Asp312 | Glu496 | [33] |
| GH38 | none | (β/α)7 | alpha | retaining | anti | 1qwn | α-mannosidase II | Drosophila melanogaster | 5-F-β-l-gulosyl | Asp341 | Asp204 | [34] |
| GH39 | A | (β/α)8 | beta | retaining | anti | 1uhv | β-xylosidase | Thermoanaerobacterium saccharolyticum | 2-F-xylosyl | Glu160 | Glu277 | [35] |
| GH42 | A | (β/α)8 | beta | retaining | anti | 1kwk | β-galactosidase | Thermus thermophylus A4 | d-galactose | Glu141 | Glu312 | [36] |
| GH44 | none | (β/α)8 | beta | retaining | anti | 2eqd | endoglucanase | Clostridium thermocellum | cellooctaose | Glu186 | Glu359 | [37] |
| GH45 | none | 6-strand. β-barrel | beta | inverting | syn | 4eng | endo-1,4-glucanase | Humicola insolens | cellohexaose | Asp121 | Asp10 | [38] |
| GH46 | I | α + β | beta | inverting | predicted syn by clan | see at GH24 | ||||||
| GH47 | none | (α/α)7 | alpha | inverting | anti | 1x9d | α-mannosidase I | Homo sapiens | Me-2-S-(α-Man)-2-thio-α-Man | Asp463 | Glu599 | [39], [40] |
| GH48 | M | (α/α)6 | beta | inverting | predicted anti by clan | see at GH8 | ||||||
| GH49 | N | β-helix | alpha | inverting | predicted anti by clan | see at GH28 | ||||||
| GH50 | A | (β/α)8 | beta | retaining | predicted anti by clan | see e.g. at GH1 | ||||||
| GH51 | A | (β/α)8 | alpha | retaining | anti | 1qw9 | α-l-arabino- furanosidase | Geobacillus stearothermophilus | PNP-l-arabino-furanoside | Glu175 | Glu294 | [41] |
| GH53 | A | (β/α)8 | beta | retaining | predicted anti by clan | see e.g. at GH1 | ||||||
| GH54 | none | β-sandwich | alpha | retaining | anti | 1wd4 | α-l-arabino- furanosidase B | Aspergillus kawachii | l-arabinofuranose | Asp297 | Glu221 | [42] |
| GH55 | none | β-helix | beta | inverting | anti | 3eqo | β-1,3-glucanase | Phanerochaete chrysosporium K-3 | d-gluconolacton | Glu633 | unknown | [43] |
| GH56 | none | (β/α)7 | beta | retaining | anti | 1fcv | hyaluronidase | Apis mellifera | (hyaluron.)4 | Glu113 | internal | [44] |
| GH57 | none | (β/α)7 | alpha | retaining | anti | 1kly | glucanotransferase | Thermococcus litoralis | acarbose | Asp214 | Glu123 | [45] |
| GH59 | A | (β/α)8 | beta | retaining | predicted anti by clan | see e.g. at GH1 | ||||||
| GH63 | G | (α/α)6 | alpha | inverting | predicted anti by clan | see at GH37 | ||||||
| GH65 | L | (α/α)6 | alpha | inverting | predicted syn by clan | see at GH15 | ||||||
| GH67 | none | (β/α)8 | alpha | inverting | syn | 1gql | α-glucuronidase | Cellvibrio japonicus Ueda107 | d-glucuronic acid | Glu292 | unknown | [46] |
| GH68 | J | 5-fold β-propeller | beta | retaining | anti | 1pt2 | levansucrase | Bacillus subtilis | sucrose | Glu342 | Asp86 | [47] |
| GH70 | H | (β/α)8 | alpha | retaining | predicted anti by clan | see e.g. at GH13 | ||||||
| GH72 | A | (β/α)8 | beta | retaining | anti | 2w62 | β-1,3-glucano- transferase | Saccharomyces cerevisiae S288C | laminaripentaose | Glu176 | Glu275 | [48] |
| GH74 | none | 7-fold β-propeller | beta | inverting | syn | 2ebs | cellobiohydrolase (OXG-RCBH) | Geotrichum sp. m128 | xyloglucan heptasaccharide | Asp465 | Asp35 | [49] |
| GH77 | H | (β/α)8 | alpha | retaining | anti | 1esw | amylomaltase | Thermus aquaticus | acarbose | Asp395 | Asp293 | [50] |
| GH79 | A | (β/α)8 | beta | retaining | predicted anti by clan | see e.g. at GH1 | ||||||
| GH80 | I | α + β | beta | inverting | predicted syn by clan | see at GH24 | ||||||
| GH83 | E | 6-fold β-propeller | alpha | retaining | predicted anti by clan | see e.g. at GH33 | ||||||
| GH84 | none | (β/α)8 | beta | retaining | anti | 2chn | β-N-acetyl- glucosaminidase | Bacteroides thetaiota- omicron VPI-5482 | NAG-thiazoline | Glu242 | internal | [51] |
| GH85 | K | (β/α)8 | beta | retaining | anti | 2w92 | endo-β-N-acetyl- glucosaminidase D | Streptococcus pneumoniae TIGR4 | NAG-thiazoline | Glu337 | internal | [52] |
| GH86 | A | (β/α)8 | beta | retaining | predicted anti by clan | see e.g. at GH1 | ||||||
| GH89 | none | (β/α)8 | alpha | retaining | anti | 2vcb | α-N-acetyl- glucosaminidase | Clostridium perfringens | PUGNAc | Glu483 | Glu601 | [53] |
| GH92 | none | (α/α)6 + β-sandw. | alpha | inverting | anti | 2ww1 | α-1,2-mannosidase | Bacteroides thetaiota- omicron VPI-5482 | thiomannobioside | Glu533 | Asp644 Asp642 | [54] |
| GH93 | E | 6-fold β-propeller | alpha | retaining | predicted anti by clan | see e.g. at GH33 | ||||||
| GH94 | none | (α/α)6 | beta | inverting | syn | 1v7x | chitobiose phosphorylase | Vibrio proteolyticus | GlcNAc | Asp492 | phosphate | [55] |
| GH95 | none | (α/α)6 | alpha | inverting | anti | 2ead | α-1,2-l-fucosidase | Bifidobacterium bifidum | Fuc-α-1,2-Gal | Glu566 | Asn423 Asp766 | [56] |
| GH97 | none | (β/α)8 | alpha | retaining + inverting | anti | 2zq0 | α-glucosidase | Bacteroides thetaiota- omicron VPI-5482 | acarbose | Glu532 | Glu508 | [57] |
| GH102 | none | double-ψ β-barrel | beta | retaining | syn | 2pi8 | lytic transglycosylase A | Escherechia coli | chitohexaose | Asp308 | none | [58] |
| GH113 | A | (β/α)8 | beta | retaining | predicted anti by clan | see e.g. at GH1 |
References
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Error fetching PMID 12741813:
Error fetching PMID 8679589:
Error fetching PMID 11560481:
Error fetching PMID 10884356:
Error fetching PMID 15299731:
Error fetching PMID 8259514:
Error fetching PMID 12203498:
Error fetching PMID 17397864:
Error fetching PMID 14715651:
Error fetching PMID 17335500:
Error fetching PMID 15130470:
Error fetching PMID 1438172:
Error fetching PMID 17455176:
Error fetching PMID 12960159:
Error fetching PMID 14659747:
Error fetching PMID 12215416:
Error fetching PMID 17905739:
Error fetching PMID 15299721:
Error fetching PMID 15292273:
Error fetching PMID 19193645:
Error fetching PMID 11937059:
Error fetching PMID 14517548:
Error fetching PMID 19097997:
Error fetching PMID 17498741:
Error fetching PMID 18981178:
Error fetching PMID 17502382:
-
Heightman, T.D. and Vasella, A.T. (1999) Recent Insights into Inhibition, Structure, and Mechanism of Configuration-Retaining Glycosidases. Angewandte Chemie-International Edition 38(6), 750-770. Article online.
- Error fetching PMID 15642336:
- Error fetching PMID 17002288:
- Error fetching PMID 18976664:
- Hrmova M, Varghese JN, De Gori R, Smith BJ, Driguez H, and Fincher GB. (2001). Catalytic mechanisms and reaction intermediates along the hydrolytic pathway of a plant beta-D-glucan glucohydrolase. Structure. 2001;9(11):1005-16. DOI:10.1016/s0969-2126(01)00673-6 |
- Error fetching PMID 12595701:
- Error fetching PMID 10508787:
- Sulzenbacher G, Mackenzie LF, Wilson KS, Withers SG, Dupont C, and Davies GJ. (1999). The crystal structure of a 2-fluorocellotriosyl complex of the Streptomyces lividans endoglucanase CelB2 at 1.2 A resolution. Biochemistry. 1999;38(15):4826-33. DOI:10.1021/bi982648i |
- Error fetching PMID 11884144:
- Error fetching PMID 14756552:
- Error fetching PMID 19279191:
- Error fetching PMID 10220321:
- Sandgren M, Berglund GI, Shaw A, Ståhlberg J, Kenne L, Desmet T, and Mitchinson C. (2004). Crystal complex structures reveal how substrate is bound in the -4 to the +2 binding sites of Humicola grisea Cel12A. J Mol Biol. 2004;342(5):1505-17. DOI:10.1016/j.jmb.2004.07.098 |
- Uitdehaag JC, Mosi R, Kalk KH, van der Veen BA, Dijkhuizen L, Withers SG, and Dijkstra BW. (1999). X-ray structures along the reaction pathway of cyclodextrin glycosyltransferase elucidate catalysis in the alpha-amylase family. Nat Struct Biol. 1999;6(5):432-6. DOI:10.1038/8235 |
- Error fetching PMID 12741813:
- Error fetching PMID 8679589:
- Allouch J, Helbert W, Henrissat B, and Czjzek M. (2004). Parallel substrate binding sites in a beta-agarase suggest a novel mode of action on double-helical agarose. Structure. 2004;12(4):623-32. DOI:10.1016/j.str.2004.02.020 |
- Error fetching PMID 11560481:
- Error fetching PMID 10884356:
- Vocadlo DJ, Davies GJ, Laine R, and Withers SG. (2001). Catalysis by hen egg-white lysozyme proceeds via a covalent intermediate. Nature. 2001;412(6849):835-8. DOI:10.1038/35090602 |
- Error fetching PMID 15299731:
- Error fetching PMID 8259514:
- Error fetching PMID 12203498:
- Garman SC, Hannick L, Zhu A, and Garboczi DN. (2002). The 1.9 A structure of alpha-N-acetylgalactosaminidase: molecular basis of glycosidase deficiency diseases. Structure. 2002;10(3):425-34. DOI:10.1016/s0969-2126(02)00726-8 |
- Error fetching PMID 17397864:
- Error fetching PMID 14715651:
- Error fetching PMID 17666401:
- Sim L, Quezada-Calvillo R, Sterchi EE, Nichols BL, and Rose DR. (2008). Human intestinal maltase-glucoamylase: crystal structure of the N-terminal catalytic subunit and basis of inhibition and substrate specificity. J Mol Biol. 2008;375(3):782-92. DOI:10.1016/j.jmb.2007.10.069 |
- Error fetching PMID 17335500:
- Error fetching PMID 15130470:
- Error fetching PMID 1438172:
- Rojas AL, Nagem RA, Neustroev KN, Arand M, Adamska M, Eneyskaya EV, Kulminskaya AA, Garratt RC, Golubev AM, and Polikarpov I. (2004). Crystal structures of beta-galactosidase from Penicillium sp. and its complex with galactose. J Mol Biol. 2004;343(5):1281-92. DOI:10.1016/j.jmb.2004.09.012 |
- Error fetching PMID 17455176:
- Error fetching PMID 12960159:
- Error fetching PMID 14659747:
- Error fetching PMID 12215416:
- Error fetching PMID 17905739:
- Error fetching PMID 15299721:
- Karaveg K, Siriwardena A, Tempel W, Liu ZJ, Glushka J, Wang BC, and Moremen KW. (2005). Mechanism of class 1 (glycosylhydrolase family 47) {alpha}-mannosidases involved in N-glycan processing and endoplasmic reticulum quality control. J Biol Chem. 2005;280(16):16197-207. DOI:10.1074/jbc.M500119200 |
- Cantú D, Nerinckx W, and Reilly PJ. (2008). Theory and computation show that Asp463 is the catalytic proton donor in human endoplasmic reticulum alpha-(1-->2)-mannosidase I. Carbohydr Res. 2008;343(13):2235-42. DOI:10.1016/j.carres.2008.05.026 |
- Hövel K, Shallom D, Niefind K, Belakhov V, Shoham G, Baasov T, Shoham Y, and Schomburg D. (2003). Crystal structure and snapshots along the reaction pathway of a family 51 alpha-L-arabinofuranosidase. EMBO J. 2003;22(19):4922-32. DOI:10.1093/emboj/cdg494 |
- Error fetching PMID 15292273:
- Error fetching PMID 19193645:
- Imamura H, Fushinobu S, Yamamoto M, Kumasaka T, Jeon BS, Wakagi T, and Matsuzawa H. (2003). Crystal structures of 4-alpha-glucanotransferase from Thermococcus litoralis and its complex with an inhibitor. J Biol Chem. 2003;278(21):19378-86. DOI:10.1074/jbc.M213134200 |
- Error fetching PMID 11937059:
- Error fetching PMID 14517548:
- Error fetching PMID 19097997:
- Error fetching PMID 17498741:
- Przylas I, Terada Y, Fujii K, Takaha T, Saenger W, and Sträter N. (2000). X-ray structure of acarbose bound to amylomaltase from Thermus aquaticus. Implications for the synthesis of large cyclic glucans. Eur J Biochem. 2000;267(23):6903-13. DOI:10.1046/j.1432-1033.2000.01790.x |
- Dennis RJ, Taylor EJ, Macauley MS, Stubbs KA, Turkenburg JP, Hart SJ, Black GN, Vocadlo DJ, and Davies GJ. (2006). Structure and mechanism of a bacterial beta-glucosaminidase having O-GlcNAcase activity. Nat Struct Mol Biol. 2006;13(4):365-71. DOI:10.1038/nsmb1079 |
- 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 |
- Ficko-Blean E, Stubbs KA, Nemirovsky O, Vocadlo DJ, and Boraston AB. (2008). Structural and mechanistic insight into the basis of mucopolysaccharidosis IIIB. Proc Natl Acad Sci U S A. 2008;105(18):6560-5. DOI:10.1073/pnas.0711491105 |
-
Zhu et al. (2010) Nature Chemical Biology in the press; DOI: 10.1038/nchembio.278 direct link.
- Hidaka M, Honda Y, Kitaoka M, Nirasawa S, Hayashi K, Wakagi T, Shoun H, and Fushinobu S. (2004). Chitobiose phosphorylase from Vibrio proteolyticus, a member of glycosyl transferase family 36, has a clan GH-L-like (alpha/alpha)(6) barrel fold. Structure. 2004;12(6):937-47. DOI:10.1016/j.str.2004.03.027 |
- Nagae M, Tsuchiya A, Katayama T, Yamamoto K, Wakatsuki S, and Kato R. (2007). Structural basis of the catalytic reaction mechanism of novel 1,2-alpha-L-fucosidase from Bifidobacterium bifidum. J Biol Chem. 2007;282(25):18497-18509. DOI:10.1074/jbc.M702246200 |
- Error fetching PMID 18981178:
- Error fetching PMID 17502382: