Effect of pH and temperature on the global compactness, structure, and activity of cellobiohydrolase Cel7A from Trichoderma harzianum

Author(s)

Colussi, Francieli ^[1] ; Garcia, Wanius ^[2] ; Rosseto, Flavio Rodolfo ^[1] ; Soares de Mello, Bruno Luan ^[1] ; de Oliveira Neto, Mario ^[1] ; Polikarpov, Igor ^[1]

Affiliation

^[1] Univ Sao Paulo, IFSC, Grp Cristalog, BR-13560970 Sao Carlos, SP - Brazil

^[2] Univ Fed Abc, CCNH, Santo Andre, SP - Brazil

• Document type: Journal article
• Source: EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS; v. 41, n. 1, p. 89-98, JAN 2012.
• Web of Science Citations: 13

Abstract

Due to its elevated cellulolytic activity, the filamentous fungus Trichoderma harzianum (T. harzianum) has considerable potential in biomass hydrolysis application. Cellulases from Trichoderma reesei have been widely used in studies of cellulose breakdown. However, cellulases from T. harzianum are less-studied enzymes that have not been characterized biophysically and biochemically as yet. Here, we examined the effects of pH and temperature on the secondary and tertiary structures, compactness, and enzymatic activity of cellobiohydrolase Cel7A from T. harzianum (Th Cel7A) using a number of biophysical and biochemical techniques. Our results show that pH and temperature perturbations affect Th Cel7A stability by two different mechanisms. Variations in pH modify protonation of the enzyme residues, directly affecting its activity, while leading to structural destabilization only at extreme pH limits. Temperature, on the other hand, has direct influence on mobility, fold, and compactness of the enzyme, causing unfolding of Th Cel7A just above the optimum temperature limit. Finally, we demonstrated that incubation with cellobiose, the product of the reaction and a competitive inhibitor, significantly increased the thermal stability of Th Cel7A. Our studies might provide insights into understanding, at a molecular level, the interplay between structure and activity of Th Cel7A at different pH and temperature conditions. (AU)

• FAPESP's process: 10/08370-3 - Biophysical and biochemical studies of exoglucanases from Trichoderma harzianum involved in the biodegradation of cellulose
• Grantee: Wanius José Garcia da Silva
• Support Opportunities: Regular Research Grants
• FAPESP's process: 09/54035-4 - Facility for advanced studies of biosystems and nanostructured materials
• Grantee: Igor Polikarpov
• Support Opportunities: Multi-user Equipment Program
• FAPESP's process: 10/16542-9 - Studies of the cellulolytic enzymes with potential in the enzymatic transformation of the sugarcane biomass using Small Angle X-ray Scattering
• Grantee: Mario de Oliveira Neto
• Support Opportunities: Scholarships in Brazil - Post-Doctoral