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Effect of carbon source on the biochemical properties of β-xylosidases produced by Aspergillus versicolor

Paper ID Volume ID Publish Year Pages File Format Full-Text
36724 45146 2004 8 PDF Available
Title
Effect of carbon source on the biochemical properties of β-xylosidases produced by Aspergillus versicolor
Abstract

The filamentous fungus Aspergillus versicolor produced large amounts of mycelial β-xylosidase activity when grown on xylan or xylose as the only carbon source. The presence of glucose drastically decreased the level of β-xylosidase activity, while cycloheximide prevented the induction of the enzymes by xylan or xylose. The β-xylosidases induced by xylose or xylan were purified by a simple protocol involving DEAE-cellulose chromatography and ammonium sulphate precipitation. The purified enzymes were acidic proteins, with carbohydrate contents of 21% for that induced by xylose, and 47% for that induced by xylan. Their apparent molecular masses, estimated by gel filtration, and optimal temperatures for β-xylosidase activities, were about 60 and 100 kDa, and 40 and 45 °C, respectively, for the enzymes induced by xylose and xylan. Xylose-induced β-xylosidase exhibited an optimum pH of 6.0, while that of the xylan-induced enzyme was 5.5. Both purified β-xylosidases exhibited also β-galactosidase, β-glucosidase and α-arabinosidase activities. In addition to synthetic substrates, the enzymes hydrolysed xylobiose and xylotriose, suggesting a physiological role. KM values for p-nitrophenyl β-d-xylopyranoside were 0.32 mM, for the xylose-induced β-xylosidase, and 0.19 mM for the xylan-induced one. Xylose competitively inhibited both β-xylosidases, with KI values of 5.3 and 2.0 mM, for the enzymes induced by xylose or xylan, respectively.

Keywords
β-Xylosidase; Xylobiase; Glycoprotein; Aspergillus versicolor
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Effect of carbon source on the biochemical properties of β-xylosidases produced by Aspergillus versicolor
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Publisher
Database: Elsevier - ScienceDirect
Journal: Process Biochemistry - Volume 39, Issue 12, 29 October 2004, Pages 1931–1938
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
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