Conformational changes and sequence analysis in cellulase from Aspergillus niger with cationic surfactant

The present study evaluates the binding of cetylpyridinium chloride (CPC) with cellulase in various experimental conditions using potentiometric, fluorescence spectroscopy and turbidimetric techniques. The analysis of binding curves revealed the existence of two sets of binding sets for CPC. The binding parameters were estimated and interpreted in terms of structural viewpoints of cellulase. The observation of turbidity suggests that CPC molecules individually nucleate around cellulase/CMC complex to form micelle-like structures. Fluorescence spectroscopy analysis of cellulase/CMC-surfactant system showed that these complexes could be compact to elucidate the mechanism of binding cellulase/CMC complex to CPC. The differential response of the enzyme/CMC to surfactant, indicates that the interaction on the complex surface is strongly ionic and hydrophobic(cooperative) in nature. A sequencing analysis was also conducted on β-1, 4-endoglucanase from A. niger (EglA) and others from family 12 in order to examine the nature of interaction involved in binding process and structure of carbohydrate-protein complexes. The results suggest that the conserved residues are located in a more hydrophobic microenvironment and apolar area energy is more than polar within enzyme structure.