PROSITE documentation PDOC00511
Glycosyl hydrolases family 9 (GH9) active sites signatures


The microbial degradation of cellulose and xylans requires several types of enzymes such as endoglucanases (EC, cellobiohydrolases (EC (exoglucanases), or xylanases (EC [1,2]. Fungi and bacteria produces a spectrum of cellulolytic enzymes (cellulases) and xylanases which, on the basis of sequence similarities, can be classified into families. One of these families is known as the cellulase family E [3] or as the glycosyl hydrolases family 9 [4,E1]. The enzymes which are currently known to belong to this family are widely distributed among bacteria, fungi, amoebozoa, invertebrate metazoans, mosses, ferns, gymnosperms, and angiosperms:

  • Butyrivibrio fibrisolvens cellodextrinase 1 (ced1).
  • Cellulomonas fimi endoglucanases B (cenB) and C (cenC).
  • Clostridium cellulolyticum endoglucanase G (celCCG).
  • Clostridium cellulovorans endoglucanase C (engC).
  • Clostridium stercoararium endoglucanase Z (avicelase I) (celZ).
  • Clostridium thermocellum endoglucanases D (celD), F (celF) and I (celI).
  • Fibrobacter succinogenes endoglucanase A (endA).
  • Pseudomonas fluorescens endoglucanase A (celA).
  • Streptomyces reticuli endoglucanase 1 (cel1).
  • Thermomonospora fusca endoglucanase E-4 (celD).
  • Dictyostelium discoideum spore germination specific endoglucanase 270-6. This slime mold enzyme may digest the spore cell wall during germination, to release the enclosed amoeba.
  • Endoglucanases from unicellular green microalgae, such as the unicellular alga Chlamydomonas reinhardtii or the colonial algae Gonium pectorale and Volvox carteri. Microalgae can utilize cellulose for growth in the absence/ limitation of other C-sources by secreting endocellulases.
  • Endoglucanases from plants such as Avocado or French bean. In plants this enzyme may be involved in the fruit ripening process.
  • Invertebrate endoglucanases, secreted by salivary glands and the gut.

Three conserved regions in these enzymes are centered on conserved residues which have been shown [5,6,7] to be important for the catalytic activity. The first region contains the characteristic DAGD motif, where the C-terminal D acts as the catalytic base that extracts a proton from the nucleophilic water. The second region contains an active site histidine and the third one contains two catalytically important residues: an aspartate and a glutamate. The fully conserved nucleophilic D forms H-bonds with the residues of the active-site loop, comprising of regions I and II, to bring it in the proper alignement. The fully conserved E acts as an acid that protonates the leaving group and stabilizes the positively-charged oxocarbonium transition-state. We have used these three regions as signature patterns, with the first pattern corresponding to region I, the second to region II and the third to region III.

Expert(s) to contact by email:

Siddiqui K.S.
Henrissat B.

Last update:

November 2018 / Text and old pattern revised; new pattern added.


Technical section

PROSITE methods (with tools and information) covered by this documentation:

GH9_1, PS60032; Glycosyl hydrolases family 9 (GH9) active site signature 1  (PATTERN)

GH9_2, PS00592; Glycosyl hydrolases family 9 (GH9) active site signature 2  (PATTERN)

GH9_3, PS00698; Glycosyl hydrolases family 9 (GH9) active site signature 3  (PATTERN)


1AuthorsBeguin P.
TitleMolecular biology of cellulose degradation.
SourceAnnu. Rev. Microbiol. 44:219-248(1990).
PubMed ID2252383

2AuthorsGilkes N.R. Henrissat B. Kilburn D.G. Miller R.C. Jr. Warren R.A.J.
TitleDomains in microbial beta-1, 4-glycanases: sequence conservation, function, and enzyme families.
SourceMicrobiol. Rev. 55:303-315(1991).
PubMed ID1886523

3AuthorsHenrissat B. Claeyssens M. Tomme P. Lemesle L. Mornon J.-P.
TitleCellulase families revealed by hydrophobic cluster analysis.
SourceGene 81:83-95(1989).
PubMed ID2806912

4AuthorsHenrissat B.
TitleA classification of glycosyl hydrolases based on amino acid sequence similarities.
SourceBiochem. J. 280:309-316(1991).
PubMed ID1747104

5AuthorsTomme P. Chauvaux S. Beguin P. Millet J. Aubert J.-P. Claeyssens M.
TitleIdentification of a histidyl residue in the active center of endoglucanase D from Clostridium thermocellum.
SourceJ. Biol. Chem. 266:10313-10318(1991).
PubMed ID2037583

6AuthorsTomme P. van Beeumen J. Claeyssens M.
TitleModification of catalytically important carboxy residues in endoglucanase D from Clostridium thermocellum.
SourceBiochem. J. 285:319-324(1992).
PubMed ID1637316

7AuthorsGuerriero G. Sergeant K. Legay S. Hausman J.-F. Cauchie H.-M. Ahmad I. Siddiqui K.S.
TitleNovel Insights from Comparative In Silico Analysis of Green Microalgal Cellulases.
SourceInt. J. Mol. Sci. 19:0-0(2018).
PubMed ID29914107


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