title: Thermal behaviour and tolerance to ionic liquid [emim]OAc in GH10 xylanase from Thermoascus aurantiacus SL16W.
abstract: GH10 xylanase from Thermoascus aurantiacus strain SL16W (TasXyn10A) showed high stability and activity up to 70-75 °C. The enzyme's half-lives were 101 h, 65 h, 63 min and 6 min at 60, 70, 75 and 80 °C, respectively. The melting point (T m), as measured by DSC, was 78.5 °C, which is in line with a strong activity decrease at 75-80 °C. The biomass-dissolving ionic liquid 1-ethyl-3-methylimidazolium acetate ([emim]OAc) in 30 % concentration had a small effect on the stability of TasXyn10A; T m decreased by only 5 °C. It was also observed that [emim]OAc inhibited much less GH10 xylanase (TasXyn10A) than the studied GH11 xylanases. The K m of TasXyn10A increased 3.5-fold in 15 % [emim]OAc with xylan as the substrate, whereas the approximate level of V max was not altered. The inhibition of enzyme activity by [emim]OAc was lesser at higher substrate concentrations. Therefore, high solid concentrations in industrial conditions may mitigate the inhibition of enzyme activity by ionic liquids. Molecular docking experiments indicated that the [emim] cation has major binding sites near the catalytic residues but in lower amounts in GH10 than in GH11 xylanases. Therefore, [emim] cation likely competes with the substrate when binding to the active site. The docking results indicated why the effect is lower in GH10.
authors: Department of Biology, Faculty of Science, Chiang Mai University, Chiang Mai, 50200, Thailand.
authors: Niwat
authors: N
authors: Chawachart
authors: Sasikala
authors: S
authors: Anbarasan
authors: Samuel
authors: S
authors: Turunen
authors: He
authors: H
authors: Li
authors: Chartchai
authors: C
authors: Khanongnuch
authors: Michael
authors: M
authors: Hummel
authors: Herbert
authors: H
authors: Sixta
authors: Tom
authors: T
authors: Granström
authors: Saisamorn
authors: S
authors: Lumyong
authors: Ossi
authors: O
authors: Turunen
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D020134:Catalytic Domain; D043364:Endo-1,4-beta Xylanases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D004795:Enzyme Stability; D006358:Hot Temperature; D007093:Imidazoles / Q000494:pharmacology*; D052578:Ionic Liquids / Q000494:pharmacology*; D062105:Molecular Docking Simulation; D008969:Molecular Sequence Data; D055327:Thermoascus / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D007093:Imidazoles; D052578:Ionic Liquids; D043364:Endo-1,4-beta Xylanases; C518739:1-ethyl-3-methylimidazolium