PROSITE documentation PDOC00877
Glycosyl hydrolases family 45 active site


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 K or as the glycosyl hydrolases family 45 [3,E1]. The enzymes which are currently known to belong to this family are listed below.

  • Endoglucanase 5 from Humicola insolens.
  • Endoglucanase 5 from Trichoderma reesei (egl5).
  • Endoglucanase K from Fusarium oxysporum.
  • Endoglucanase B from Pseudomonas fluorescens (celB).
  • Endoglucanase 1 from Ustilago maydis (egl1).

The best conserved regions in these enzymes is located in the N-terminal section. It contains an aspartic acid residue which has been shown [4] to act as a nucleophile in the catalytic mechanism. We use this region as a signature pattern.

Expert(s) to contact by email:

Henrissat B.

Last update:

November 1997 / Pattern and text revised.


Technical section

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

GLYCOSYL_HYDROL_F45, PS01140; Glycosyl hydrolases family 45 active site  (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. Bairoch A.
TitleNew families in the classification of glycosyl hydrolases based on amino acid sequence similarities.
SourceBiochem. J. 293:781-788(1993).
PubMed ID8352747

4AuthorsDavies G.J. Dodson G.G. Hubbard R.E. Tolley S.P. Dauter Z. Wilson K.S. Hjort C. Mikkelsen J.M. Rasmussen G. Schuelein M.
TitleStructure and function of endoglucanase V.
SourceNature 365:362-364(1993).
PubMed ID8377830


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