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 E  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:
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
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