Enzymes activity and stability at extreme temperature can be intensified by regularly applying protein engineering. In the present study, two amino acids were perceived to mark the temperature dependability of xylanase from Geobacilhcc thennodenitrificans C5. Six mutants of G. thermodenitrificans C5 were built through site directed mutagenesis by interchanging the residue with proline and glutamic acid (R81P, H82E, W185P, D186E, double mutant W185P/D186E and triple mutant H82E/W185P/D186E). Both mutant and wild type enzymes were quantified in host E. coli BL21. In comparison to wild type, the temperature was enhanced by 4 degrees C, 5 degrees C and 11 degrees C in H82E, W185P/D186E and H82E/W185P/D186E mutant models, respectively. The mutant H82E and the combined substitutions (H82E/W185P/D186E) showed the most pronounced shifts in their half-lives for thermal inactivation. Half-life was increased 13 times at 60 degrees C, 15 times at 65 degrees C, 9 times at 70 degrees C and 5 times at 75 degrees C by H82E/W185P/D186E mutant. Mutations in xylanase enzyme causes rigidification of essential chain and filling of groove that leads to stabilization of mutants and finally resulted into enhancement in their thermostability.