Browsing by Author "Krisna Septiningrum"

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    The C-terminal region of xylanase domain in Xyn11A from Paenibacillus curdlanolyticus B-6 plays an important role in structural stability
    (Springer Verlag, 2014) Junjarus Sermsathanaswadi; Somsak Pianwanit; Patthra Pason; Rattiya Waeonukul; Chakrit Tachaapaikoon; Khanok Ratanakhanokchai; Krisna Septiningrum; Akihiko Kosugi
    Paenibacillus curdlanolyticus B-6 produces an extracellular multienzyme complex containing a major xylanase subunit, designated Xyn11A, which includes two functional domains belonging to glycosyl hydrolase family-11 (GH11) and carbohydrate binding module family-36 (CBM36) and possesses a glycine and asparagine-rich linker (linker). To clarify the roles of each functional domain, recombinant proteins XynXL and XynX (CBM36 deleted and CBM36 and linker deleted, respectively) were constructed. Their xylanase activities were similar toward soluble xylan, whereas XynXL showed decreased hydrolysis activity toward insoluble xylan while XynX had no xylanase activity. To determine the significance of the linker and its neighbor region, XynX was subjected to secondary structural alignments using circular dichroism (CD) spectroscopy and three-dimensional (3D) structural analysis. A seven amino acid (NTITIGG) neighbor linker sequence was highly conserved among GH11 xylanases of Paenibacillus species. Although XynX exhibited a typical GH11 xylanase structure, conformational gaps were observed in the _6- and _12-sheets and in CD spectra. Flipping of the Arg163 side chains in the subsite was also observed upon analysis of superimposed models. Docking analysis using xylohexaose indicated that flipping of the Arg163 side chains markedly affected substrate binding in the subsite. To identify the amino acids related to stabilizing the substrate binding site, XynX with an extended C-terminal region was designed. At least seven amino acids were necessary to recover substrate binding and xylanase activity. These results indicated that the seven amino acid neighbor Xyn11A linker plays an important role in the activity and conformational stability of the xylanase domain. © 2014, Springer-Verlag Berlin Heidelberg.
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    The GH67 _-glucuronidase of Paenibacillus curdlanolyticus B-6 removes hexenuronic acid groups and facilitates biodegradation of the model xylooligosaccharide hexenuronosyl xylotriose
    (Elsevier Inc., 2015) Krisna Septiningrum; Hiroshi Ohi; Rattiya Waeonukul; Patthra Pason; Chakrit Tachaapaikoon; Khanok Ratanakhanokchai; Junjarus Sermsathanaswadi; Lan Deng; Panida Prawitwong; Akihiko Kosugi
    4-O-Methylglucuronic acid (MeGlcA) side groups attached to the xylan backbone through _-1,2 linkages are converted to hexenuronic acid (HexA) during alkaline pulping. _-Glucuronidase (EC 3.2.1.139) hydrolyzes 1,2-linked MeGlcA from xylooligosaccharides. To determine whether _-glucuronidase can also hydrolyze HexA-decorated xylooligosaccharides, a gene encoding _-glucuronidase (AguA) was cloned from Paenibacillus curdlanolyticus B-6. The purified protein degraded hexenuronosyl xylotriose (_X3), a model substrate prepared from kraft pulp. AguA released xylotriose and HexA from _X3, but the Vmax and kcat values for _X3 were lower than those for MeGlcA, indicating that HexA side groups may affect the hydrolytic activity. To explore the potential for biological bleaching, _X3 degradation was performed using intracellular extract from P. curdlanolyticus B-6. The intracellular extract, with synergistic _-glucuronidase and _-xylosidase activities, degraded _X3 to xylose and HexA. These results indicate that _-glucuronidase can be used to remove HexA from _X3 derived from pulp, reducing the need for chemical treatments in the pulping process. � 2015 Elsevier Inc.