An alpha-glucuronidase of Schizophyllum commune acting on polymeric xylan.
The main alpha-glucuronidase (EC 3.2.1.131) of the fungus Schizophyllum commune was purified to homogeneity using standard chromatographic methods; anion exchange, hydrophobic interaction chromatography and gel filtration. The enzyme had a molecular mass of 125 kDa as determined by SDS-polyacrylamide gel electrophoresis and a pI value of 3.6 according to isoelectric focusing. The N-terminal amino acid sequence of the S. commune alpha-glucuronidase did not show any homology with other alpha-glucuronidases. It exhibited maximal activity at pH values from 4.5 to 5.5 and was stable for 24 h between pH 6 and 8 at 40 degrees C. The highest temperature at which the enzyme retained its full activity for 24 h at pH 5.8 was 40 degrees C. The alpha-glucuronidase of S. commune was able to remove almost all 4-O-methylglucuronic acid groups from water-soluble polymeric softwood arabinoglucuronoxylans. The action of the enzyme on birchwood acetyl-glucuronoxylan was limited due to the high amount of acetyl substituents. The degree of hydrolysis of partially soluble deacetylated glucuronoxylan did not exceed 50% of the theoretical maximum. However, together with a xylanase hydrolysing the xylan backbone the action of the alpha-glucuronidase of S. commune on glucuronoxylan was clearly enhanced. It was apparent that the enzyme was able to remove the 4-O-methylglucuronic groups mainly from soluble substrates.
Tenkanen
M
M
VTT Biotechnology, FIN-02044, VTT, Finland. maijia.tenkanen@vtt.fi
Siika-aho
M
M
D000595:Amino Acid Sequence; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004591:Electrophoresis, Polyacrylamide Gel; D006026:Glycoside Hydrolases / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011108:Polymers / Q000378:metabolism*; D012567:Schizophyllum / Q000201:enzymology*; D013379:Substrate Specificity; D014990:Xylans / Q000378:metabolism*
D011108:Polymers; D014990:Xylans; D006026:Glycoside Hydrolases; C096734:alpha-glucuronidase