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KMID : 0364820090450040332
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Korean Journal of Microbiology
2009 Volume.45 No. 4 p.332 ~ p.338
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Characterization of an Extracellular Xylanase from Bacillus sp. HY-20, a Bacterium in the Gut of Apis mellifera
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Lee Lan-Hee
Kim Do-Young
Han Mi-Kyoung
Oh Hyun-Woo
Ham Su-Jin
Park Doo-Sang
Bae Kyung-Sook
Sok Dai-Eun
Shin Dong-Ha
Son Kwang-Hee
Park Ho-Yong
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Abstract
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A xylan-decomposing bacterium, HY-20, was isolated from the gut of a honeybee, Apis mellifera, and identified as Bacillus sp. The extracellular GH11 xylanase (XylP) gene (687-bp) of strain HY-20 encoded a protein of 228 amino acids with a deduced molecular mass of 25,522 Da and a calculated pI of 9.33. The primary structure of XylP was 97% identical to that of B. pumilus xylanase (GenBank accession no.: AY526092) that has not been characterized yet. The recombinant His-tagged enzyme (rXylP) overexpressed in Escherichia coli BL21 harboring pET-28a(+)/xylP was purified to electrophoretic homogeneity by cation exchange and gel permeation chromatographies. The purified enzyme exhibited the highest catalytic activity toward birchwood xylan at pH 6.5 and 50oC and retained approximately 50% of its original activity when pre-incubated at 55oC for 15 min. The recombinant enzyme was completely inactivated by Hg2+ (1 mM) and N-bromosuccinimide (5 mM), while its activity was slightly stimulated by approximately 10% in the presence of Mn2+ (1 mM), Fe2+ (1 mM), and sodium azide (5 mM). rXylP was able to efficiently degrade various polymeric xylose-based substrates but PNP-sugar derivatives and glucose-based polymers were not susceptible to the enzyme.
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KEYWORD
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Apis mellifera, Bacillus sp. HY-20, bee, gut bacterium, xylanase
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