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A bifunctional β-xylosidase-xylose isomerase from Streptomyces sp. EC 10

par Belfaquih, Najia ;Penninckx, Michel
Référence Enzyme and microbial technology, 27, 1-2, page (114-121)
Publication Publié, 2000

Article révisé par les pairs

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Résumé :

β-Xylosidase (1, 4-β-D-xylan xylohydrolase EC 3.2.1.37) and xylose isomerase (D-xylose ketol-isomerase EC 5.3.1.5) produced by Streptomyces sp. strain EC 10, were cell-bound enzymes induced by xylan, straw, and xylose. Enzyme production was subjected to a form of carbon catabolite repression by glycerol. β-Xylosidase and xylose isomerase copurified strictly, and the preparation was found homogeneous by gel electrophoresis after successive chromatography on DEAE-Sephacel and gel filtration on Biogel A. Streptomyces sp. produced apparently a bifunctional β-xylosidase-xylose isomerase enzyme. The molecular weight of the enzyme was measured to be 163, 000 by gel filtration and 42, 000 by SDS-PAGE, indicating that the enzyme behaved as a tetramer of identical subunits. The Streptomyces sp. β-xylosidase was a typical glycosidase acting as an exoenzyme on xylooligosaccharides, and working optimally at pH 7.5 and 45°C. The xylose isomerase optimal temperature was 70°C and maximal activity was observed in a broad range pH (5-8). Enhanced saccharification of arabinoxylan caused by the addition of the enzyme to endoxylanase suggested a cooperative enzyme action. The first 35 amino acids of the N-terminal sequence of the enzyme showed strong analogies with N-terminal sequences of xylose isomerase produced by other microorganisms but not with other published N-terminal sequences of β-xylosidases. © 2000 Elsevier Science Inc.