title: Unusual hydrophobic linker region of beta-glucosidase (BGLII) from Thermoascus aurantiacus is required for hyper-activation by organic solvents.
abstract: A gene encoding a putative beta-glucosidase was isolated from Thermoascus aurantiacus IFO9748 and designated as bgl2. The recombinant enzyme showed beta-glucosidase activity when p-nitrophenyl-beta-glucose (pNP-Glc) was used as substrate. We also found that the enzyme activity was increased in the presence of organic solvents. An addition of 20 % (v/v) 1-octanol resulted in 54-fold higher activity of pNP-Glc hydrolysis, and transglycosylation activity was also found to be activated. The results of tryptophan fluorescence spectral analysis revealed the changes in the tertiary structure of the enzyme in the presence of 1-hexanol that may cause increased enzyme activity. BGLII has a distinctive hydrophobic linker region between N- and C-terminal domains. A chimeric enzyme in which the linker region was substituted by the corresponding region of another beta-glucosidase failed to be activated by organic solvents, suggesting that the hydrophobic linker region may act as a molecular switch in BGLII.
authors.affiliation: Laboratory of Applied Microbiology, Research Institute of Natural Resources, Ishikawa Prefectural University, Nonoichi-cho, Ishikawa, 921-8836, Japan.
authors.forename: Jiong
authors.initials: J
authors.lastname: Hong
authors.forename: Hisanori
authors.initials: H
authors.lastname: Tamaki
authors.forename: Hidehiko
authors.initials: H
authors.lastname: Kumagai
mesh_terms: D020003:1-Octanol / Q000494:pharmacology*; D003001:Cloning, Molecular; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D020536:Enzyme Activators / Q000494:pharmacology*; D032641:Eurotiales / Q000201:enzymology*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D000441:Hexanols / Q000494:pharmacology; D057927:Hydrophobic and Hydrophilic Interactions; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA; D013050:Spectrometry, Fluorescence; D001617:beta-Glucosidase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
chemical_list: D004271:DNA, Fungal; D020536:Enzyme Activators; D005656:Fungal Proteins; D000441:Hexanols; D011994:Recombinant Proteins; C036260:1-hexanol; D001617:beta-Glucosidase; D020003:1-Octanol