## 8 Discovered and Characterized Mono-Modular Processive Endoglucanase Properties
[45] was similar to the patterns reported for the _Constridium thermocellum_ noncellulosomal GH9 endoplasmic GH9B (Cell) [131] and the _Saccharomyces degradans_ GH5 endoglucanase Cel5H [133]. Both the _Constridium thermocellum_ noncellulosomal GH9 endoglucanase GH9B (Cell) and the _Saccharomyces degradans_ GH5 endoglucanase Cel5H were shown to be processive endoglucanases with cellobiose as the main hydrolytic end product [133; 133]. Arguably, the carboxymethyl substitution on cellulose in the CMC may prevent cellulases in hydrolyzing CMC in a processive manner, thus questioning the suitability of CMC as a substrate for processivity study [131]. Secondly, \(p\)NP-cellobioside has been recognized as a chromogenic substrate to measure exocellulase activity [74]. Kinetic activities of this cellulase GH5-p4818 Cel5_2A on \(p\)NP-cellobioside, as reported by [PERSON] et al. [45], suggest that GH5-p4818 Cel5_2A, as a recognized endoglucanase, had an exocating catalytic property. However, [PERSON] and [PERSON] [132] cautioned that activity on \(p\)NP-cellobioside was a function of where and how well this synthetic substrate compound could bind into the active site of an enzyme and would not predict whether an enzyme was an exocellase or endocellulase. Determination of the processivity value with purified cellulose substrates can help define the processive nature of endocellulases and this has been demonstrated in the past in several studies. The processivity value was determined with filter paper (Whatman #1) for the _Thermobifida fusca_ processive endoglucanase Cel9A (E4) (at 7.0) [120], for the _Constridiumthermoellum_ noncellulosomal processive endoglucanase GH9B (Cell, at about 50) [131], and for the three _Saccharophagus degradans_ GH5 processive endoglucanases of Cel5G, Cel5H and Cel5J (at 4.0-4.6) [133]. The processivity value was measured with Avicel for the brown rot _Basidiumcycete Glycoephylum trabeum_ GH5 processive endoglucanase Cel5A (at 11.3) [118]. The processivity value was determined with phosphoric acid-swollen cellulose (PASC) for the _Clostridium cellulolyticum_ cellulosomal GH9 processive endoglucanase CelF (at 19.0) [129]. The processivity value was increased from 2.4 to 3.9 when the incubation was prolonged from 0.5 to 3.5 h with the soluble amorphous cellulose substrate RAC for the _Clostridium Phytofermentans_ GH9 processive endoglucanase Cel9. The processivity value was also seen increasing from 3.6 to 8.6 when the incubation was prolonged from 0.5 to 24 h with filter paper for the processive GH5 endoglucanase EG1 in an atypical white rot basidomycete _Volvariella voluacea_[117]. Meanwhile, the processivity value was also determined with filter paper for the _Thermobifida fusca_ non-processive endoglucanase Cel6A (E2, at 2.1 and 2.6) [120,133] and the _Clostridium thermocellum_ cellulosomal non-processive endoglucanase GH9C (CbhA, at 1.9) [132]. [PERSON] et al. [133] reviewed that the processivity values, measured with filter paper for the extensively characterized _Thermobifida fusca_ processive endoglucanase Cel9A, typically ranged between 3.0 and 7.0 for processive endoglucanases. GH5-tCel5A1 and GH5-p4818 Cel5_2A were determined to have a processivity value of 10 and 4.6, respectively [45,127]. Thus, determination of processivity values is affected by types of substrates and duration of incubation time used.