title: Directed evolution for engineering pH profile of endoglucanase III from Trichoderma reesei.
abstract: The potential of cellulase has been revealed not only in biomass conversion but also in various industrial processes, including food, textiles, laundry, pulp, and paper. Due to the need for alkali-tolerant cellulase with high specific activity at alkaline pH, for example, for application in detergent industry an error-prone PCR approach was employed for enhancing the alkali-tolerant ability of endoglucanase III (EG III) from Trichoderma reesei by error-prone PCR. One mutant (N321T) which exhibited an optimal activity at pH 5.4, corresponded to a basic shift of 0.6 pH unit compared to the wild-type enzyme, was selected and characterized. In addition, two site-directed mutations, N321D and N321H, were designed to study the role of residue at position 321. As expected, the N321D mutation changed enzyme's optimal activity to pH 4.0, resulting in a large decrease in the specific activity. However, the N321H mutated enzyme was active over a broader pH range compared to the wild type, with no much change in the specific activity. These properties suggest that the residue at position 321 is important amino acid residue in determining the pH activity profile of the EG III from T. reesei.
authors.affiliation: State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, PR China.
authors.forename: Ting
authors.initials: T
authors.lastname: Wang
authors.forename: Xiangmei
authors.initials: X
authors.lastname: Liu
authors.forename: Qian
authors.initials: Q
authors.lastname: Yu
authors.forename: Xi
authors.initials: X
authors.lastname: Zhang
authors.forename: Yinbo
authors.initials: Y
authors.lastname: Qu
authors.forename: Peiji
authors.initials: P
authors.lastname: Gao
authors.forename: Tianhong
authors.initials: T
authors.lastname: Wang
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics*; D002480:Cellulase / Q000737:chemistry / Q000235:genetics*; D019020:Directed Molecular Evolution / Q000379:methods; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D014242:Trichoderma / Q000201:enzymology* / Q000235:genetics
chemical_list: D002480:Cellulase