The microbial degradation of cellulose and xylans requires several types of enzymes such as endoglucanases (EC 3.2.1.4), cellobiohydrolases (EC 3.2.1.91) (exoglucanases), or xylanases (EC 3.2.1.8) [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 [3] or as the glycosyl hydrolases family 9 [4,E1]. The enzymes which are currently known to belong to this family are listed below.

• Butyrivibrio fibrisolvens cellodextrinase 1 (ced1).
• 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 plants such as Avocado or French bean. In plants this enzyme may be involved the fruit ripening process.

Two of the most conserved regions in these enzymes are centered on conserved residues which have been shown [5,6], in the endoglucanase D from Cellulomonas thermocellum, to be important for the catalytic activity. The first region contains an active site histidine and the second region contains two catalytically important residues: an aspartate and a glutamate. We have used both regions as signature patterns.