title: Biocatalytic properties and substrate-binding ability of a modular GH10 β-1,4-xylanase from an insect-symbiotic bacterium, Streptomyces mexicanus HY-14.
abstract: The gene (1350-bp) encoding a modular β-1,4-xylanase (XylU), which consists of an N-terminal catalytic GH10 domain and a C-terminal carbohydrate-binding module 2 (CBM 2), from Streptomyces mexicanus HY-14 was cloned and functionally characterized. The purified His-tagged recombinant enzyme (rXylU, 44.0 kDa) was capable of efficiently hydrolyze diverse xylosidic compounds, p-nitrophenyl-cellobioside, and p-nitrophenyl-xylopyranoside when incubated at pH 5.5 and 65°C. Especially, the specific activities (649.8 U/mg and 587.0 U/mg, respectively) of rXylU toward oat spelts xylan and beechwood xylan were relatively higher than those (<500.0 U/mg) of many other GH10 homologs toward the same substrates. The results of enzymatic degradation of birchwood xylan and xylooligosaccharides (xylotriose to xylohexaose) revealed that rXylU preferentially hydrolyzed the substrates to xylobiose (>75%) as the primary degradation product. Moreover, a small amount (4%<) of xylose was detected as the degradation product of the evaluated xylosidic substrates, indicating that rXylU was a peculiar GH10 β-1,4-xylanase with substrate specificity, which was different from its retaining homologs. A significant reduction of the binding ability of rXylU caused by deletion of the C-terminal CBM 2 to various insoluble substrates strongly suggested that the additional domain might considerably contribute to the enzyme-substrate interaction.
authors.affiliation: Industrial Bio-materials Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, 305-806, Republic of Korea.
authors.forename: Do Young
authors.initials: DY
authors.lastname: Kim
authors.forename: Dong-Ha
authors.initials: DH
authors.lastname: Shin
authors.forename: Sora
authors.initials: S
authors.lastname: Jung
authors.forename: Jong Suk
authors.initials: JS
authors.lastname: Lee
authors.forename: Han-Young
authors.initials: HY
authors.lastname: Cho
authors.forename: Kyung Sook
authors.initials: KS
authors.lastname: Bae
authors.forename: Chang-Keun
authors.initials: CK
authors.lastname: Sung
authors.forename: Young Ha
authors.initials: YH
authors.lastname: Rhee
authors.forename: Kwang-Hee
authors.initials: KH
authors.lastname: Son
authors.forename: Ho-Yong
authors.initials: HY
authors.lastname: Park
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004795:Enzyme Stability; D005965:Glucuronates / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007313:Insecta / Q000382:microbiology; D008969:Molecular Sequence Data; D008970:Molecular Weight; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D009844:Oligosaccharides / Q000378:metabolism; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D013302:Streptomyces / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D013379:Substrate Specificity; D013696:Temperature; D014990:Xylans / Q000378:metabolism*; D014994:Xylose / Q000378:metabolism
chemical_list: D004269:DNA, Bacterial; D005965:Glucuronates; D050505:Mutant Proteins; D009844:Oligosaccharides; D011994:Recombinant Proteins; D014990:Xylans; C570991:xylooligosaccharide; D014994:Xylose; D043364:Endo-1,4-beta Xylanases