The microbial degradation of cellulose and xylans requires several types of
enzymes such as endoglucanases (EC 22.214.171.124), cellobiohydrolases (EC 126.96.36.199)
(exoglucanases), or xylanases (EC 188.8.131.52) [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 D  or as the glycosyl hydrolases
family 8 [4,E1]. The enzymes which are currently known to belong to this
family are listed below.
Acetobacter xylinum endonuclease cmcAX.
Bacillus strain KSM-330 acidic endonuclease K (Endo-K).
Cellulomonas josui endoglucanase 2 (celB).
Cellulomonas uda endoglucanase.
Clostridium cellulolyticum endoglucanases C (celcCC).
Clostridium thermocellum endoglucanases A (celA).
Erwinia chrysanthemi minor endoglucanase y (celY).
The most conserved region in these enzymes is a stretch of about 20 residues
that contains two conserved aspartate. The first asparatate is thought  to
act as the nucleophile in the catalytic mechanism. We have used this region as
a signature pattern.
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