Arabinoxylan-degrading enzyme system of the fungus Aspergillus awamori: purification and properties of an alpha-L-arabinofuranosidase.
An alpha-L-arabinofuranosidase produced by the fungus Aspergillus awamori had a molecular mass of approximately 64 kDa on sodium dodecyl sulphate/polyacrylamide gel electrophoresis (SDS-PAGE) and was optimally active at pH 4.6 and 50 degrees C. The enzyme, which chromatographed as a single component on SDS-PAGE, appeared to consist of two isoenzymes of pI 3.6 and 3.2. Acting in isolation, the alpha-L-arabinofuranosidase had only a very limited capacity to release L-arabinose (less than 11%) directly from arabinoxylans that had been extracted from a number of plant cell wall preparations using 18% alkali, but a much higher proportion of the L-arabinose (46%) was released from a wheat straw arabinoxylan that had been isolated by steam treatment. There was a marked synergistic effect between the alpha-L-arabinofuranosidase and an endo-(1 --> 4)-beta-D-xylanase produced by A. awamori in both the rate and extent of the release of L-arabinose from both oat straw and wheat straw arabinoxylans, suggesting that L-arabinose-substituted oligosaccharides generated by the endoxylanase action were better substrates for enzyme action. A novel property of the alpha-L-arabinofuranosidase was its capacity to release a substantial proportion (42%) of feruloyl L-arabinose from intact wheat straw arabinoxylan. The concerted action of the alpha-L-arabinofuranosidase and endoxylanase released 71% of the feruloyl L-arabinose and 69% of the p-coumaroyl L-arabinose substituents from wheat straw arabinoxylan.
Wood
T M
TM
Rowett Research Institute, Bucksburn, Aberdeen, UK.
McCrae
S I
SI
D001089:Arabinose / Q000378:metabolism; D001230:Aspergillus / Q000201:enzymology*; D002852:Chromatography, Ion Exchange; D002523:Edible Grain; D004591:Electrophoresis, Polyacrylamide Gel; D005656:Fungal Proteins / Q000302:isolation & purification* / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000302:isolation & purification* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008970:Molecular Weight; D006109:Poaceae; D013379:Substrate Specificity; D014934:Wood; D014990:Xylans / Q000378:metabolism*
D005656:Fungal Proteins; D014990:Xylans; C085118:arabinoxylan; D001089:Arabinose; D006026:Glycoside Hydrolases; C019713:alpha-N-arabinofuranosidase