Cloning and Characterization of Xylanase 11B Gene from Paenibacillus woosongensis

Paenibacillus woosongensis의 Xylanase 11B 유전자 클로닝과 특성분석

A gene coding for the xylanase predicted from the partial genomic sequence of Paenibacillus woosongensis was cloned by PCR amplification and sequenced completely. This xylanase gene, designated xyn11B, consisted of 1,071 nucleotides encoding a polypeptide of 356 amino acid residues. Based on the deduced amino acid sequence, Xyn11B was identified to be a modular enzyme, including a single carbohydrate-binding module besides the catalytic domain, and was highly homologous to xylanases belonging to glycosyl hydrolase family 11. The SignalP4.1 server predicted a stretch of 26 residues in the N-terminus to be the signal peptide. Using DEAE-Sepharose and Phenyl-Sepharose column chromatography, Xyn11B was partially purified from the cell-free extract of recombinant Escherichia coli carrying a copy of the P. woosongensis xyn11B gene. The partially purified Xyn11B protein showed maximal activity at $50^{\circ}C$ and pH 6.5. The enzyme was more active on arabinoxylan than on oat spelt xylan and birchwood xylan, whereas it did not exhibit activity towards carboxymethylcellulose, mannan, and para-nitrophenyl-${\beta}$-xylopyranoside. The activity of Xyn11B was slightly increased by $Ca^{2+}$ and $Mg^{2+}$, but was significantly inhibited by $Cu^{2+}$, $Ni^{2+}$, $Fe^{3+}$, and $Mn^{2+}$, and completely inhibited by SDS.

Paenibacillus woosongensis의 유전체 부분 염기서열로부터 유추된 xylanase 유전자를 PCR 증폭하여 클로닝하고 염기서열을 결정하였다. 클로닝된 xylanase 유전자는 xyn11B로 명명되었으며, 356 아미노산으로 구성된 단백질을 코드하는 1,071 뉴클레오티드로 이루어졌다. Xyn11B의 아미노산 배열을 분석한 결과 glycosyl hydrolase family 11에 속하는 xylanase와 상동성이 높은 활성영역과 탄수화물 결합영역을 포함하고 있는 다영역 효소로 확인되었다. SignalP4.1 server로부터 아미노 말단의 26개 잔기가 signal peptide로 예측되었다. DEAE-Sepharose와 Phenyl-Separose 컬럼 크로마토그래피 과정을 통해 xyn11B 유전자를 함유한 재조합 대장균의 균체 파쇄상등액으로부터 Xyn11B를 부분 정제하였다. 부분 정제된 Xyn11B의 반응특성을 조사한 결과 pH 6.5와 $50^{\circ}C$에서 최대 반응활성을 보였고 birchwood xylan이나 oat spelt xylan보다 arabinoxylan에 대한 활성이 높았으며 셀룰로스, 만난과 para-nitrophenyl-${\beta}$-xylopyranoside에 대해서는 분해활성이 없었다. Xyn11B의 활성은 $Ca^{2+}$과 $Mg^{2+}$에 의해서는 약간 증가한 반면에 $Cu^{2+}$, $Ni^{2+}$, $Fe^{3+}$, $Mn^{2+}$에 의해서는 크게 저해되었고 SDS에 의해서 완전히 저해되었다.