Improvement of the catalytic performance of a hyperthermostable GH10 xylanase from Talaromyces leycettanus JCM12802

- An acidic thermostable xylanase of GH10 (TlXyn10A) was identified in T.leycettanus.
- Sequence analysis revealed seven residues probably involved in substrate contacting.
- Mutant TlXyn10A_P with modifications at subsites +2 to +4 showed improved properties.
- TlXyn10_P in combination with cellulase released the most reducing sugar form wheat straw.

A xylanase gene of GH 10, Tlxyn10A, was cloned from Talaromyces leycettanus JCM12802 and expressed in Pichia pastoris. Purified recombinant TlXyn10A was acidic and hyperthermophilic, and retained stable over the pH range of 2.0-6.0 and at 90 °C. Sequence analysis of TlXyn10A identified seven residues probably involved in substrate contacting. Three mutants (TlXyn10A_P, _N and _C) were then constructed by substituting some or all of the residues with corresponding ones of hyperthermal Xyl10C from Bispora sp. MEY-1. TlXyn10A_P with mutations at subsites +2 to +4 exhibited improved specific activity (by 0.44-fold) and pH stability (2.0-10.0). Molecular dynamics simulation analysis indicated that mutations E229I and F232E probably weaken the substrate affinity at subsites +3 to +4, and G149D may introduce a new hydrogen bond. These modifications altogether account for the improved performance of TlXyn10A_P. Moreover, TlXyn10A_P was able to hydrolyze wheat straw persistently, and has the application potentials in various industries.