Xylanase

About: Xylanase is a research topic. Over the lifetime, 7099 publications have been published within this topic receiving 163793 citations.

Enzymatic treatments reveal differential capacities for xylan recognition and degradation in primary and secondary plant cell walls.

Abstract: The capacity of four xylan-directed probes (carbohydrate-binding modules CfCBM2b-1-2 and CjCBM15; monoclonal antibodies LM10 and LM11) to recognize xylan polysaccharides in primary and secondary cell walls of tobacco stem sections has been determined. Enzymatic removal of pectic homogalacturonan revealed differential recognition of xylans in restricted regions of cortical primary cell walls. Monoclonal antibody binding to these exposed xylans was more sensitive to xylanase action than carbohydrate-binding module (CBM) binding. In contrast, the recognition of xylans by CBMs in secondary cell walls of the same organ was more sensitive to xylanase action than the recognition of xylans by the monoclonal antibodies. A methodology was developed to quantify indirect immunofluorescence intensities, and to evaluate xylanase impacts. The four xylan probes were also used to detect xylan populations in chromatographic separations of solubilized cell wall materials from tobacco stems. Altogether, these observations reveal the heterogeneity of the xylans in plant cell walls. They indicate that although CBM and antibody probes can exhibit similar specificities against solubilized polymers, they can have differential capacities for xylan recognition in muro, and that the access of molecular probes and enzymes to xylan epitopes/ligands also varies between primary and secondary cell walls that are present in the same organ.

An analysis of the extracellular xylanases and cellulases of Butyrivibrio fibrisolvens H17c.

Abstract: The extracellular xylanase and cellulase components of Butyrivibrio fibrisolvens H17c were investigated. Two major peaks of enzyme activity were eluted by hydroxylapatite chromatography and designated complex A (CA), having cellulase activity, and complex B (CB) having predominantly xylanase activity but with some activity on carboxymethyl cellulose (CMC). CB was further purified on a DE-52 column and subjected to gel filtration. The xylanase and CMCase activities eluted in a single peak with an apparent molecular mass greater than thyroglobulin (Mr 669 000). CMC xymograms of polyacrylamide gels electrophoresed under non-denaturing conditions indicated the presence of five bands with CMCase activity from CA and eight from CB. Xylan xymograms under the same conditions indicated the presence of four bands of activity in CB. Under mild denaturing conditions the xylanase activity in CB was found in 11 bands with molecular mass ranging from 45 to 180 and the CMCase activity in three bands with molecular mass ranging from 45 kDa to 60 kDa. This indicates that CB exists as a multi-subunit protein aggregate of xylanases, some of which also have cellulase activity.

Purification, characterization and regulation of the synthesis of an Aspergillus nidulans acidic xylanase.

Abstract: An acidic xylanase from a culture filtrate of Aspergillus nidulans grown on oat-spelt xylan was purified to apparent homogeneity. The purified enzyme showed a single band on sodium dodecyl sulphate-polyacrylamide gel electrophoresis with a molecular mass of 34,000 Da and had an isoelectric point of approximately 3.4. The enzyme was a non-debranching endoxylanase highly specific for xylans. The xylanase showed an optimal activity at pH 6.0 and 56° C and had a Michaelis constant Km of 0.97 mg oat-spelt xylan (soluble fraction) ml and a maximed reaction velocity (Vmax) of 1,091 μmol min−1 (mg−1protein)−1. Using polyclonal antibodies raised against the purified enzyme, the regulation of its synthesis has been studied. The xylanase production is repressed by glucose and induced by oat-spelt xylan, arabinoxylan, 4-O-methylglucurono-xylan, birchwood xylan and xylose.

Purification and Characterization of a [beta]-D-Xylosidase and an Endo-Xylanase from Wheat Flour

Abstract: A [beta]-D-xylosidase and an endo-xylanase were purified from European wheat (Triticum aestivum) flour. The [beta]-D-xylosidase had a molecular weight of approximately 64,000 and an isoelectric point of 5.5. It hydrolyzed p-nitrophenyl-[beta]-D-xylopyranoside and xylo-oligosaccharides and released D-xylose units from wheat arabinoxylan and oat spelts xylan. An endo-xylanase with a molecular weight of approximately 55,000 was also obtained and it consisted of a number of isoforms with isoelectric points between 4.0 and 5.0. The action of the isolated endo-xylanase depended on the degree of substitution of the polysaccharide. Unbranched polymers were preferentially hydrolyzed. Since xylo-oligosaccharides were not hydrolyzed, the enzyme appeared to need at least five or more consecutive unsubstituted xylose units. Finally, an [alpha]-L-arabinofuranosidase that hydrolyzed p-nitrophenyl-[alpha]-L-arabinofuranoside was partially purified.