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MetaCyc Pathway: xyloglucan degradation III (cellobiohydrolase)
Inferred from experiment

Enzyme View:

Pathway diagram: xyloglucan degradation III (cellobiohydrolase)

This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.

Superclasses: Degradation/Utilization/AssimilationCarbohydrates DegradationPolysaccharides DegradationXyloglucan Degradation
Degradation/Utilization/AssimilationPolymeric Compounds DegradationPolysaccharides DegradationXyloglucan Degradation

Some taxa known to possess this pathway include : Aspergillus nidulans, Geotrichum sp. M128, Neosartorya fischeri NRRL 181

Expected Taxonomic Range: Fungi

General Background

Xyloglucan is the major component of the hemicellulose in dicotyledon type I cell walls. The cross-linking between xyloglucan chains is a major factor in the stability of the three-dimensional matrix between adjacent cellulose microfibrils [Whitney95].

Xyloglucan has a backbone of β-1,4-linked cellotetraose units, which are substituted in C-6 by α-D-xylosyl residues at two or three of the first four glucosyl residues (but not the residue closest to the reducing end) [York93]. Some of the xylosyl residues are subsequently further substituted by (1,2)-β-D-galactosyl residues at the second and/or third xylose residue and by (1,2)-α-L-fucose at the galactosyl unit of the third xylose residue [Madson03, Lerouxel06].

A common terminology uses G for basic non-substituted glucosyl units within a xylosylglycan, X for glucose residues substituted by α-D-xylose, L for glucose residues substituted by α-D-xylose and β-D-galactose, and F for glucose residues substituted by α-D-xylose, β-D-galactose and α-L-fucose [Fry93]. Using this terminology, most xylosylglucans consist of repeating heptasaccharide XXXG units as well further modified XXLG, XLXG, and XLLG units.

About This Pathway

The enzyme described in this pathway has been originally isolated from the fungus Geotrichum sp. M128. It is an exoglucanase that recognizes and attacks the reducing end of oligoxyloglucan, releasing segments composed of two glucosyl residues (with their xylose modifications) from the main xyloglucan chain (a modified cellobiohydrolase activity). For example, when the enzyme acts on the reducing end of the oligoxyloglucan heptasaccharide XXXG, it produces the tetrasaccharide XX and the trisaccharide XG.

A thorough study of the substrate specificity showed that the terminal residue (site +2) must be an unbranched glucose. The glycosylation of the glucose at site +1 is not important, thus the reducing end unit that is being cleaved may be GG, XG, or LG. It is also important that the third glucose residue from the reducing end (site -1) is branched with a unmodified xylose residue [Yaoi02].

An enzyme with similar properties has been characterized from the fungus Aspergillus nidulans [Bauer05].

Variants: (1,4)-β-xylan degradation, xyloglucan degradation I (endoglucanase), xyloglucan degradation II (exoglucanase)

Created 31-May-2011 by Caspi R, SRI International


Bauer05: Bauer S, Vasu P, Mort AJ, Somerville CR (2005). "Cloning, expression, and characterization of an oligoxyloglucan reducing end-specific xyloglucanobiohydrolase from Aspergillus nidulans." Carbohydr Res 340(17);2590-7. PMID: 16214120

Fry93: Fry, S. C., York, W. S., Albersheim, P., et al (1993). "An unambiguous nomenclature for xyloglucan-derived oligosaccharides." Physiol Plant 89, 1-3.

Lerouxel06: Lerouxel O, Cavalier DM, Liepman AH, Keegstra K (2006). "Biosynthesis of plant cell wall polysaccharides - a complex process." Curr Opin Plant Biol 9(6);621-30. PMID: 17011813

Madson03: Madson M, Dunand C, Li X, Verma R, Vanzin GF, Caplan J, Shoue DA, Carpita NC, Reiter WD (2003). "The MUR3 gene of Arabidopsis encodes a xyloglucan galactosyltransferase that is evolutionarily related to animal exostosins." Plant Cell 15(7);1662-70. PMID: 12837954

Mishra09: Mishra, A., Malhotra, A. V. (2009). "Tamarind xyloglucan: a polysaccharide with versatile application potential." Journal of Materials Chemistry 19:85288536.

Whitney95: Whitney, S. E. C., Brigham, J. E., Darke, A. H., Reid, J. S. G., Gidley, M. J. (1995). "In vitro assembly of cellulose/xyloglucan networks: ultrastructure and molecular aspects." Plant J 8, 491-504.

Yaoi02: Yaoi K, Mitsuishi Y (2002). "Purification, characterization, cloning, and expression of a novel xyloglucan-specific glycosidase, oligoxyloglucan reducing end-specific cellobiohydrolase." J Biol Chem 277(50);48276-81. PMID: 12374797

York93: York WS, Harvey LK, Guillen R, Albersheim P, Darvill AG (1993). "Structural analysis of tamarind seed xyloglucan oligosaccharides using beta-galactosidase digestion and spectroscopic methods." Carbohydr Res 248;285-301. PMID: 8252539

Other References Related to Enzymes, Genes, Subpathways, and Substrates of this Pathway

68: "Dental profile: dentist of the President of the Republic." (1968). J Philipp Dent Assoc 21(1);42-3. PMID: 5242597

Grishutin04: Grishutin SG, Gusakov AV, Markov AV, Ustinov BB, Semenova MV, Sinitsyn AP (2004). "Specific xyloglucanases as a new class of polysaccharide-degrading enzymes." Biochim Biophys Acta 1674(3);268-81. PMID: 15541296

Latendresse13: Latendresse M. (2013). "Computing Gibbs Free Energy of Compounds and Reactions in MetaCyc."

Yaoi04: Yaoi K, Kondo H, Noro N, Suzuki M, Tsuda S, Mitsuishi Y (2004). "Tandem repeat of a seven-bladed beta-propeller domain in oligoxyloglucan reducing-end-specific cellobiohydrolase." Structure 12(7);1209-17. PMID: 15242597

Yaoi07: Yaoi K, Kondo H, Hiyoshi A, Noro N, Sugimoto H, Tsuda S, Mitsuishi Y, Miyazaki K (2007). "The structural basis for the exo-mode of action in GH74 oligoxyloglucan reducing end-specific cellobiohydrolase." J Mol Biol 370(1);53-62. PMID: 17498741

Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by Pathway Tools version 19.5 (software by SRI International) on Wed May 4, 2016, biocyc13.