Study of structural and molecular interaction for the catalytic activity of cellulases: An insight in cellulose hydrolysis for higher bioethanol yield

Comparative sequence alignment, molecular modeling and docking analyses were performed taking 5 microbial (3 bacteria and 2 fungi) cellulase enzymes and its substrate beta-D glucose in order to understand the enzyme-substrate interaction and binding affinity associated with cellulose hydrolysis. Amino acids such as Val114, Ala255, Val288, Val289, and Ser301 of Streptomyces sp. Endoglucanase-1 shown to bind with beta-D glucose. The binding energy between the modeled cellulase and substrate complex resulted that Endoglucanase-1 from Streptomyces sp. has the most binding affinity of -5.61 kcal/mol for the cellulose unit. Deleterious mutations in cellulase enzyme, E133A and H98A reported previously in Dickeya dadantii have been designed and validated using in silico approach. The number of hydrogen bond interactions reported in wild type Endoglucanase-1 from Streptomyces sp. was 22, whereas E133A and H98A mutant cellulase from Dickeya dadantii, the interaction number comes down to 5 and 6 respectively. Binding energy recorded for these two mutants is -4.52 and -4.91 respectively which is less than its wild type form. Phylogenetic tree analysis suggests that the modeled cellulase enzyme from Streptomyces sp. is closely related to the cellulase from Thermobispora bispora, Cellulomonas fimi, Streptomyces halstedii organisms. The cellulose-binding site in Endoglucanase E of Clostridium thermocellum is Ser131, Met263, Gln298 and His310 which are reported to have differed with Ala119, Ala255, Ser298 and Cys304 in Streptococcus sp. Endoglucanase 1. These molecular modeling and docking studies revealed that different microbial cellulase enzymes have potential towards the use of cellulose as a substrate for the high yield of bioethanol. (C) 2019 Elsevier B.V. All rights reserved.