Endoxylanase substrate selectivity determines degradation of wheat water-extractable and water-unextractable arabinoxylan.
The relative activity of an endoxylanase towards water-unextractable (WU-AX) and water-extractable arabinoxylan (WE-AX) substrates, referred to as endoxylanase substrate selectivity, impacts the enzyme functionality in cereal-based biotechnological processes such as bread-making and gluten starch separation. A set of six endoxylanases representing a range of substrate selectivities as determined by a screening method using chromophoric substrates [Anal. Biochem.2003, 319, 73-77] was used to examine the impact of such selectivity on changes in structural characteristics of wheat WU-AX and WE-AX upon enzymic hydrolysis. While WE-AX degradation by the selected endoxylanases was very comparable with respect to apparent molecular mass (MM) profiles and arabinose to xylose ratio of the hydrolysates formed, WU-AX solubilisation and subsequent degradation of solubilised fragments gave rise to widely varying MM profiles, depending on the substrate selectivity of the enzymes. Enzymes with high selectivity towards WU-AX de facto generated higher MM fragments from WU-AX than enzymes with low selectivity. The arabinose to xylose ratios of solubilised fragments were independent of the degree of solubilisation.
Moers
Karolien
K
Katholieke Universiteit Leuven, Laboratory of Food Chemistry, Kasteelpark Arenberg 20, B-3001 Leuven, Belgium. karolien.moers@agr.kuleuven.ac.be
Celus
Inge
I
Brijs
Kristof
K
Courtin
Christophe M
CM
Delcour
Jan A
JA
D001089:Arabinose / Q000737:chemistry; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry*; D006868:Hydrolysis; D013379:Substrate Specificity; D014908:Triticum / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D014990:Xylans / Q000737:chemistry*; D014994:Xylose / Q000737:chemistry
D014990:Xylans; D014867:Water; C085118:arabinoxylan; D014994:Xylose; D001089:Arabinose; D043364:Endo-1,4-beta Xylanases