Evolutionary Relationships and Taxa-Specific Conserved Signature Indels Among Cellulases of Archaea, Bacteria, and Eukarya.

The cellulases from different cellulolytic organisms have evolutionary relationships, which range from single-celled prokaryotes to the complex eukaryotes of the living world. This in silico analysis revealed the presence of a conserved cellulase domain along with evolutionary relationships among cellulases from several species of Archaea, Bacteria, and Eukarya. The amino acid sequences of cellulases from Archaea and Bacteria showed closer identity with their domain or phylum members that provided insights into convergent and divergent evolution of cellulases from other enzymes with different substrate specificities. Evolutionary relatedness was also observed in phylogenetic trees among a number of cellulase sequences of diverse taxa. In cellulases, propensity for alanine, glycine, leucine, serine, and threonine was high, but low for cysteine, histidine, and methionine. Catalytic aspartic acid had a higher propensity than glutamic acid, and both were involved in regular expression patterns. Characteristic group and multigroup-specific conserved signature indels located in the catalytic domains of cellulases were observed that further clarified evolutionary relationships. These indels can be distinctive molecular tools for understanding phylogeny and identification of unknown cellulolytic species of common evolutionary descent in different environments.