The microbial degradation of cellulose and xylans requires several types of
enzymes such as endoglucanases (EC 126.96.36.199), cellobiohydrolases (EC 188.8.131.52)
(exoglucanases), or xylanases (EC 184.108.40.206) [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  to act
as a nucleophile in the catalytic mechanism. We use this region as a signature
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