Cellulase summary

The summary of cellulase mode of action in Table I reviews mainly data reported during the last five years. An excellent comprehensive review article on cellulase mode of action based on information reported prior to 1973 is given by Nisizawa (55). 

Table II. Summary of Various Cellulase Activity Assays Incu- bation Volume Time Temp Product ...

Oxidation of two out of 13 tryptophan residues in a cellulase from Penicillium notatum resulted in a complete loss of enzymic activity (59). There was an interaction between cellobiose and tryptophan residues in the enzyme. Participation of histidine residues is also suspected in the catalytic mechanism since diazonium-l-H-tetrazole inactivated the enzyme. A xylanase from Trametes hirsuta was inactivated by N-bromosuc-cinimide and partially inactivated by N-acetylimidazole (60), indicating the possible involvement of tryptophan and tyrosine residues in the active site. As with many chemical modification experiments, it is not possible to state definitively that certain residues are involved in the active site since inactivation might be caused by conformational changes in the enzyme molecule produced by the change in properties of residues distant from the active site. However, from a summary of the available evidence it appears that, for many / -(l- 4) glycoside hydrolases, acidic and aromatic amino acid residues are involved in the catalytic site, probably at the active and binding sites, respectively. 

Cellobiase. Figure 2 outlines the general purification steps used to isolate a pure cellobiase (named for its function in the cellulase complex) and three forms of the hydrocellulase. In purifying cellobiase it was expedient to replace the adsorption or affinity column with a batch separation on DEAE-Sephadex A-50 and to complete the purification with cation exchange chromatography on SP-Sephadex (49, 50). Table IV is a summary of the purification of the cellobiase and co-purification of... 

The latest summary of separation and purification of cellulases and related enzymes is written by Hashimoto and Nisizawa 17). Their list... 

Fig. 18.1 Summary of steps involved in the regulation of cellulase and hemiceUulase gene expression in T. reesei...

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