5-05: Construction of chimeric enzymes based on catalytic domains of cellulytic enzymes from insect-gut bacterium

Gut of an insect, Helicoverpa armigera, living on cotton plant was found to inhabit many cellulytic bacteria. Three hydrolytic enzymes of one such bacterium, Paenibacillus sp, were characterized and expressed heterologously.  All three enzymes, namely b-1,4-endoglucanase (Endo5A), b-glucosidase (Gluc1C) and b-1,4-endoxylanase (Xyl11D), demonstrated optimal activities at 50 ^oC and pH 6-7. To reduce the cost of heterologous production of these enzymes, we synthesized two chimeric bifunctional enzymes (a) based on catalytic domains of Endo5A and Xyl11D and (b) based on catalytic domains of Endo5A and Gluc1C. Both these chimeric enzymes exhibited dual catalytic functions and higher specific activities towards their substrates as compared to their individual counter parts. The results indicate that these chimeric bifunctional enzymes have high potential for hydrolyzing lignocellulosic biomass for biofuel production.