A cellulose-binding module of the Trichoderma reesei @b-mannanase Man5A increases the mannan-hydrolysis of complex substrates
Publikation/Tidskrift/Serie: Journal of Biotechnology
Endo-@b-1,4-d-mannanases (@b-mannanase; EC 188.8.131.52) are endohydrolases that participate in the degradation of hemicellulose, which is closely associated with cellulose in plant cell walls. The @b-mannanase from Trichoderma reesei (Man5A) is composed of an N-terminal catalytic module and a C-terminal carbohydrate-binding module (CBM). In order to study the properties of the CBM, a construct encoding a mutant of Man5A lacking the part encoding the CBM (Man5A@DCBM), was expressed in T. reesei under the regulation of the Aspergillus nidulans gpdA promoter. The wild-type enzyme was expressed in the same way and both proteins were purified to electrophoretic homogeneity using ion-exchange chromatography. Both enzymes hydrolysed mannopentaose, soluble locust bean gum galactomannan and insoluble ivory nut mannan with similar rates. With a mannan/cellulose complex, however, the deletion mutant lacking the CBM showed a significant decrease in hydrolysis. Binding experiments using activity detection of Man5A and Man5A@DCBM suggests that the CBM binds to cellulose but not to mannan. Moreover, the binding of Man5A to cellulose was compared with that of an endoglucanase (Cel7B) from T. reesei.
- Carbohydrate-binding module
- ISSN: 0168-1656