0- Glucan cellobiohydrolase

Cellobiohydrolase I (CBH I, 1,4-jS-D-glucan-cellobiohydrolase, E.C. 3.2.1.91) is the main protein (ca. 60%) of the cellulase complex produced by T. reesei strains. CBH I hydrolyses crystalline cellulose, acid swollen cellulose and 4-methylumbelliferyl-cellodex-trins by cleaving off the terminal cellobiose unit from the non reducing end of the chain. It operates with retention of configuration in the reaction products 19,20. The abundance of this enzyme and its stability has facihtated its purification to homogeneity... 

Cellulase-Negative Xylanase-Positive Mutants. There are two reports concerning the selection of such mutants from filamentous fungi, one on Pofyporus adm-tus (32) and the other cmi Trichoderma reesei (Durand, H. et al. Society CAYLA, Toulouse, France, unpublished results). An analysis of the eliminated cellulase genes has not been done, so it is not known if the mutants negative in endo(l- 4)-p-glucan-ase were deficient also in cellobiohydrolases. 

Native or processed cellulose (e.g., cotton, Avicel, filter paper) and its soluble derivatives (e.g., CMC, HEC3) are substrates most often used in the study of cellulases. The classification based on the use of these substrates (l,4-/ -D-glucan cellobiohydrolases (CBH), exo-cellulases, Avicelases and... 

Microorganisms use several types of extracellular enzymes to degrade cellulose to glucose exoglucanases (l,4-/ -D-glucan cellobiohydrolases,... 

Enzymes involved in rp endo- 3-l,4-glucanase, exo-P-l,4-cellobiohydrolase. Enzymes involved in r2 exo-P-l,4-cellobiohydrolase, exo-P-l,4-glucan glucohydrolase. Enzymes involved in r3 P-bludosidse or cellobiases. 

D-glucan glucohydrolases (EC 3.2.1.74), which liberate D-glucose from l,4-/3-D-glucans and hydrolyze D-cellobiose slowly, and 1,4-/3-D-glucan cellobiohydrolase (EC 3.2.1.91), which liberates D-cellobiose from... 

Work in several laboratories (22, 27, 55, 56) has shown a pattern of cellulase action in cellulolytic organisms which requires at least one of a set of three closely related enzymes in order to hydrolyze crystalline cellulose effectively. These enzymes often possess little ability to degrade either CM-cellulose (as measured viscosimetrically) or crystalline cellulose. Nevertheless they are characterized by the capacity to cleave swollen cellulose or cellooligosaccharides almost entirely to cellobiose by virtue of their / -( - 4)glucan cellobiohydrolase activity. Recognition of this pattern has been difficult because prior to this report the three enzymes had not been purified and characterized apart from contaminating enzyme activity. 

Pilnik al (7) have noted that the combined action of pecti-nases and C-1 (1,4-p-D-glucan cellobiohydrolase, E.C. 3.2.1.91) enriched cellulases are able to almost completely liquefy pulped fruits and vegetables. For the actual dissolution of the cristal-line cellulose fibrils the C-1 enzyme is necessary which splits off cellobiose from the non-reducing end of the 1,4-p-D-glucan and which needs some C-x (1,4-p-D-glucan-glucanohydrolase, E.C. 3.2.1.4) to create such points of attack. Preparations rich in C-1 activity are usually obtained from Trichoderma spp. (8). 

Cellobiohydrolase (1,4-D-glucan cellobiohydrolase) is an exo-glucanase that catalyzes the hydrolysis of (l,4)-p-D-glucosidic linkages in cellulose with the release of cellobiose. Various forms of this enzyme are thought to hydrolyze cellulose chains either from the reducing or from the nonreducing end." " ... 

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