Mode of action of family 10 and 11 endoxylanases on water-unextractable arabinoxylan.
Microbial endo-beta-1,4-xylanases (EXs, EC 3.2.1.8) belonging to glycanase families 10 and 11 differ in their action on water-unextractable arabinoxylan (WU-AX). WU-AX was incubated with different levels of a Thermoascus aurantiacus family 10 and a Sporotrichum thermophile family 11 endoxylanases. At 10 g l(-1) arabinoxylan, enzyme concentrations (KE values) needed to obtain half-maximal hydrolysis rates (V(max) values) were 4.4 nM for the xylanase from T. aurantiacus and 7.1 nM for the xylanase from S. thermophile. Determination of Vmax/KE revealed that the family 10 enzyme hydrolysed two times more efficiently WU-AX than the family 11 enzyme. Molecular weights of the products formed were assessed and separation of feruloyl-oligosaccharides was achieved by anion-exchange and size-exclusion chromatography (SEC). The main difference between the feruloylated products by xylanases of family 10 and 11 concerned the length of the products containing feruloyl-arabinosyl substitution. The xylanase from T. aurantiacus liberated from WU-AX a feruloyl arabinoxylodisaccharide (FAX2) as the shortest feruloylated fragment in contrast with the enzyme from S. thermophile, which liberated a feruloyl arabinoxylotrisaccharide (FAX3). These results indicated that different factors govern WU-AX breakdown by the two endoxylanases.
Vardakou
Maria
M
Biotechnology Laboratory, Chemical Engineering Department, National Technical University of Athens, 5 Iroon Polytechniou Str., Zografou Campus, 15700 Athens, Greece.
Katapodis
Petros
P
Samiotaki
Martina
M
Kekos
Dimitris
D
Panayotou
George
G
Christakopoulos
Paul
P
D001671:Biochemistry / Q000379:methods; D002850:Chromatography, Gel / Q000379:methods; D002852:Chromatography, Ion Exchange / Q000379:methods; D003373:Coumaric Acids / Q000032:analysis / Q000378:metabolism; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry / Q000378:metabolism*; D032641:Eurotiales / Q000201:enzymology*; D006868:Hydrolysis; D009844:Oligosaccharides / Q000032:analysis / Q000378:metabolism; D013053:Spectrophotometry / Q000379:methods; D013175:Sporothrix / Q000201:enzymology*; D014867:Water; D014990:Xylans / Q000737:chemistry / Q000378:metabolism*
D003373:Coumaric Acids; D009844:Oligosaccharides; D014990:Xylans; D014867:Water; C085118:arabinoxylan; C004999:ferulic acid; D043364:Endo-1,4-beta Xylanases