PROSITE documentation PDOC00563
Glycosyl hydrolases family 6 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 B [3] or as the glycosyl hydrolases family 6 [4,E1]. The enzymes which are currently known to belong to this family are listed below.

  • Agaricus bisporus exoglucanase 3 (cel3).
  • Cellulomonas fimi endoglucanase A (cenA).
  • Cellulomonas fimi exoglucanase A (cbhA).
  • Microspora bispora endoglucanase A (celA).
  • Streptomyces halstedii endoglucanases A (celA1).
  • Streptomyces strain KSM-9 endoglucanase 1 (casA).
  • Thermomonospora fusca endoglucanase E-2 (celB).
  • Trichoderma reesei exoglucanase II (CBH2).

One of the conserved regions in these enzymes contains a conserved aspartic acid residue which is potentially involved [5] in the catalytic mechanism; the aspartate is followed by a cysteine which is involved in a disulfide bond [6]. A second conserved region contains an aspartate which seems [5] to be the proton donor in the catalytic mechanism. We have used both regions as signature patterns.

Expert(s) to contact by email:

Henrissat B.

Last update:

May 2004 / Text revised.


Technical section

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

GLYCOSYL_HYDROL_F6_1, PS00655; Glycosyl hydrolases family 6 signature 1  (PATTERN)

GLYCOSYL_HYDROL_F6_2, PS00656; Glycosyl hydrolases family 6 signature 2  (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

5AuthorsRouvinen J. Bergfors T. Teeri T.T. Knowles J.K. Jones T.A.
TitleThree-dimensional structure of cellobiohydrolase II from Trichoderma reesei.
SourceScience 249:380-386(1990).
PubMed ID2377893

6AuthorsGilkes N.R. Claeyssens M. Aebersold R. Henrissat B. Meinke A. Morrison H.D. Kilburn D.G. Warren R.A.J. Miller R.C. Jr.
TitleStructural and functional relationships in two families of beta-1,4-glycanases.
SourceEur. J. Biochem. 202:367-377(1991).
PubMed ID1761039


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