ORIGINAL RESEARCH: Assaying sensitivity of fungal xylanases to proteinaceous inhibitors from a rye extract: Two GH10 family xylanases resistant to XIP-like inhibitors

Abstract

Sensitivity of selected fungal xylanases to cereal proteinaceous inhibitors was assayed using a novel viscometric method based on changes in viscosity of water extracts of rye flour (a native extract and heat-treated to inactivate inhibitors) under the action of enzymes. Two of six xylanases isolated from the fungus Chrysosporium lucknowense were found to be insensitive to rye xylanase-inhibitor–protein–like (XIP-like) inhibitors, a property rarely encountered among fungal xylanases. Both enzymes belong to family 10 of glycoside hydrolases; they have been classified respectively as Xyn10B and Xyn10C. Xyn10B possessed a higher specific activity against arabinoxylan and is thus a promising candidate for use as an animal-feed additive and in other cereal-based applications involving xylan processing. Structural features responsible for the enzyme resistance to XIP-like inhibitors are discussed.