CAZypedia needs your help! We have many unassigned GH, PL, CE, AA, GT, and CBM pages in need of Authors and Responsible Curators.
Scientists at all career stages, including students, are welcome to contribute to CAZypedia. Read more here, and in the 10th anniversary article in Glycobiology.
New to the CAZy classification? Read this first.
*
Consider attending the 15th Carbohydrate Bioengineering Meeting in Ghent, 5-8 May 2024.

Glycoside Hydrolase Family 74

From CAZypedia
Revision as of 20:35, 13 June 2010 by Takuya Ishida (talk | contribs)
Jump to navigation Jump to search
Under construction icon-blue-48px.png

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.


Glycoside Hydrolase Family GH74
Clan none, 7-fold β-propeller
Mechanism inverting
Active site residues known
CAZy DB link
http://www.cazy.org/GH74.html


Substrate specificities

Glycoside hydrolases of this family hydrolyze β-1,4-linkages of various glucans. With one exception of Cel74 from Thermotoga maritima, all biochemically characterized enzymes are specific toward xyloglucans and/or xyloglucan-oligosaccharides. Cel74 from Thermotoga maritima have highest activity on barley β-glucan, but still have 20% activity on xyloglucan. A wide diversity in mode of action by GH-74 enzymes have been reported. OXG-RCBH from Geotrichum sp. M128 and OREX from Emericella nidulans formerly known as Aspergillus nidulans are active on only xyloglucan oligosaccharides and have no ability to degrade xyloglucan polymer. They release oligosaccharides with two glucose units from non-reducing end of xyloglucan oligosaccharides [1]. On the other hands, GH-74 enzymes designated as xyloglucanase; xyloglucan specific endo-β-1,4-glucanases: XEG; and xyloglucan hydrolases: Xgh, exhibit endo-type activity on xyloglucan from tamarind seed which is well investigated xyloglucan. Many of GH-74 xyloglucanases hydrolyze glycosidic linkage of unbranched glucose residue, but several members including OXG-RCBH, OREX, and Cel74A from Hypocrea jecorina formerly known as Trichoderma reesei are accommodated to accept the side-chain xylose residues at active site.


Kinetics and Mechanism

Family 74 enzymes are inverting enzymes, as shown by NMR analysis on Xeg74 from Thermobifida fusca and XEG from Geotrichum sp. M128.

Catalytic Residues

Crystal structure of OXG-RCBH demonstrated that Asp35 and Asp465 are located in the middle of the binding cleft, and its crucial roles in hydrolytic activity were experimentally confirmed by using site-directed mutagenesis [2]. The corresponding Asp residues in Clostridium thermocellum are nicely located between subsite -1 and +1 in the complex structure [3].

Three-dimensional structures

Over all structure of GH-74 enzymes consist of a tandem repeat of two seven-bladed β-propeller domains. The two domains form a open cleft substrate binding site at the interface. Catalytic residues are located in the middle of the cleft. One side of the binding cleft of OXG-RCBH are blocked by 'exo-loop' which is found only in exo-acting enzyme in this family. Crystal structure of complex with xyloglucan oligo-saccharides elucidated the interaction towards side-chain of the substrate by the enzymes [2, 3].

Family Firsts

First stereochemistry determination
Xeg74 from Thermobifida fusca by 1H-NMR [4].
First gene cloning
EglC from Aspergillus niger [5].
First general acid residue identification
OXG-RCBH from Geotrichum sp. M128 [2].
First general base residue identification
OXG-RCBH from Geotrichum sp. M128 [2].
First 3-D structure
OXG-RCBH from Geotrichum sp. M128 [2].

References

  1. Yaoi K and Mitsuishi Y. (2002). Purification, characterization, cloning, and expression of a novel xyloglucan-specific glycosidase, oligoxyloglucan reducing end-specific cellobiohydrolase. J Biol Chem. 2002;277(50):48276-81. DOI:10.1074/jbc.M208443200 | PubMed ID:12374797 [REF2]
  2. Yaoi K, Kondo H, Noro N, Suzuki M, Tsuda S, and Mitsuishi Y. (2004). Tandem repeat of a seven-bladed beta-propeller domain in oligoxyloglucan reducing-end-specific cellobiohydrolase. Structure. 2004;12(7):1209-17. DOI:10.1016/j.str.2004.04.020 | PubMed ID:15242597 [REF4]
  3. Martinez-Fleites C, Guerreiro CI, Baumann MJ, Taylor EJ, Prates JA, Ferreira LM, Fontes CM, Brumer H, and Davies GJ. (2006). Crystal structures of Clostridium thermocellum xyloglucanase, XGH74A, reveal the structural basis for xyloglucan recognition and degradation. J Biol Chem. 2006;281(34):24922-33. DOI:10.1074/jbc.M603583200 | PubMed ID:16772298 [REF5]
  4. Irwin DC, Cheng M, Xiang B, Rose JK, and Wilson DB. (2003). Cloning, expression and characterization of a family-74 xyloglucanase from Thermobifida fusca. Eur J Biochem. 2003;270(14):3083-91. DOI:10.1046/j.1432-1033.2003.03695.x | PubMed ID:12846842 [REF3]
  5. Hasper AA, Dekkers E, van Mil M, van de Vondervoort PJ, and de Graaff LH. (2002). EglC, a new endoglucanase from Aspergillus niger with major activity towards xyloglucan. Appl Environ Microbiol. 2002;68(4):1556-60. DOI:10.1128/AEM.68.4.1556-1560.2002 | PubMed ID:11916668 [REF1]

All Medline abstracts: PubMed