Introduction.- Material and Methods.- Selection of sequences, 3D structures and multiple sequence alignment.- Mutant generation.- Energy minimization.- Stereo-chemical quality check and analysis of non-bonded interactions.- Protein-protein docking.- InterProScan.- Identification of functionally important regions of wild type viz. Endo-1, 4-beta xylanases (1YNA).- 3d2GO server: From protein 3D structure to Gene Ontology (GO) term.- Results and discussions.- Conclusion.