Comparative analyses of enzymatic activity, structural study and docking of fungal cellulases

Abstract

Aspergillus cellulase was observed to show superior hydrolysis of microcrystalline cellulose (Avicel PH101) when compared to Trichoderma cellulase. In silico physicochemical characterization revealed the acidic nature of selected fungal cellulases. GRAVY index for Aspergillus and Trichoderma cellulase was -0.314 and -0.374, respectively. Negative values of GRAVY index for both the fungal cellulases indicate that these enzymes have better interaction with water. Secondary structures such as alpha helices (34.44%) and random coils (54.21%) were found to be dominant in A. niger and T. longibrachiatum cellulase, respectively. Validation results for homology modeled 3D structures of selected cellulases indicated their fine quality. The analyses revealed that 96.7 and 92.4% residues of the constructed cellulase models of A. niger and T. longibrachiatum were placed in the favored region, respectively with > 82 ERRAT overall quality factor and have > 0.7 QMEAN 4 score. ProSA evaluation revealed that the Z-score for A. niger and T. longibrachiatum cellulase was -9.2 and -6.78, respectively. Energy minimization results revealed that the potential energies -7.140 x 10(5) kJ/mol and -1.228 x 10(6) kJ/mol were found remaining constant after 744 and 1431 steps for A. niger and T. longibrachiatum cellulases, respectively. Molecular docking study revealed that TRP 200, THR 201 and GLU 160 residues from A. niger cellulase and ASP 220, GLN 196, TYR 192 and TYR 168 residues from T. longibrachiatum cellulase interact with the cellulose. Studies such as this could prove to be helpful in terms of formulating cellulase enzyme for the purpose of industrial use.