Does CMC (carboxy methylcellulose) require all the three groups of cellulases (namely endoglucanases, cellobiohydrolases and b-glucosidase) for degradation?
Or, does it only require endoglucanases for its degradation, and therefore is known as CMCase?
Endoglucanases are called as CMCase and degrade CMC only. This is because endoglucanase cleave the beta-1,4-glycosidic linkage present in CMC. Therefore as it cleave the bond in the inner part of the CMC it in called as endoglucanase. U can also say it as beta-1,4-endoglucanase. Reference: Lee and Koo, 2001
For more detail refer the book: Enzyme Technology by Ashok Pandey, Colin Webb, CArlos Ricardo Soccol and Christian Larroche
Endoglucanase are the group of cellulases which can cleave the beta 1-4 glycosidic bond from the middle of the polymeric cellulose chain and moreover can act only on amorphous forms of cellulose. Carboxy methyl cellulose is an artificial form of cellulose which is highly amorphous in nature and is soluble form also. Therefore endoglucanase activity is generally calculated using CMC salts as substrates and the englucanase activity is also generally termed as CMC'ase activity. In this activity either viscosity reduction of observed with time or reducing sugar formed is assayed using DNS method of sugar estimation. Hope I have been able to answer to your query. Best of luck of your research work..... Best regards. Deepti
As its name tells, carboxymethylcellulose carries many substituents that make it soluble, hence highly accessible to hydrolytic enzymes. However, the substituents hamper access of the substrate to the active site. Therefore, hydrolysis by exoglucanases, such as cellobiohydrolases, stops very quickly as soon as the enzyme hits a substituted residue. Endoglucanases, being able to reach sites inside the CMC chains that carry few or no substituents, have a mcuh higher activity. However, their activity on native cellulose is poor due to low substrate accessibility. Beta-glucosidases are only active on cellobiose and oligosaccharides generated by endo-and exocellulases from macromolecular cellulose
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