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KMID : 0545119960060020079
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Journal of Microbiology and Biotechnology
1996 Volume.6 No. 2 p.79 ~ p.85
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Overproduction, Purification, and Characterization of Bacillus stearothermophilus Endo-xylanase A (XynA)
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Cho, Ssang Goo
Suh, Jung Han/Choi, Yong Jin
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Abstract
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By using a T7 expression system, a large amount of Bacillus stearothermophilus endo-xylanase A (XynA) could be produced in Escherichia coli cells. The overproduced enzyme formed inclusion bodies, and so the protein could be more easily purified to homogeneity. The molecular weight of the purified enzyme was estimated to be 22 kDa by SDS-polyacrylamide gel electrophoresis and 43 kDa by Sephacryl S-200 gel filtration, suggesting that the native enzyme was a homodimer. The pI value was determined to be 8.4. The Michaelis constants for birchwood xylan and oat spelts xylan were calculated to be 3.83 ㎎/㎖ and 5.03 ㎎/㎖, respectively, and the V_max values for both xylans were 2.86μmole/min. The purified enzyme was most active at 55℃ and pH 8.0, and stable up to 60℃ and in the near neutral pH range. From the zymogram, Bacillus stearothermophilus was found to have at least three xylanases and the purified one was the smallest among them.
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