Abstract
가정에서 제조된 된장으로부터 분리된 Bacillus licheniformis WL-12의 mannanase 유전자를 크로닝하여 그 염기서열을 결정한 결과 mannanase 유전자는 360 아미노산으로 구성된 단백질을 코드하며 1,080 뉴클레오티드로 이루어졌다. 아미노산 잔기배열을 분석한 결과 WL-12의 mannanase는 GH family 26에 속하는 B. licheniformis DSM13의 mannanase와 동일하였다. B. lichenifromis WL-12의 mannanase 유전자를 함유한 재조합대장균의 균체파쇄상등액으로부터 부분정제된 효소를 사용하여 반응특성을 조사하였다. pH 6.0과 <TEX>$65^{\circ}C$</TEX>에서 최대 반응활성을 보였으며, locust bean gum (LBG)과 konjac의 분해능은 높으나 guar gum의 분해능은 낮았다. Mannanase로 LBG와 mannooligosaccharides를 분해하였을 때 mannose, mannobiose와 mannotriose가 주된 최종 반응산물로 관찰되었으며 mannobiose는 분해하지 못하였으나 이보다 중합도가 큰 mannooligosaccharides은 분해하였다. A gene encoding the mannanase of Bacillus licheniformis WL-12, which had been isolated from Korean soybean paste, was cloned into Escherichia coli and nucleotide sequence of the mannanase gene was subsequently determined. The mannanase gene consisted of 1,080 nucleotides encoding a polypeptide of 360 amino acid residues. The deduced amino acid sequence was identical to that of putative mannanase from B. liceniformis DSM13 belonging to GH family 26. The mannanase was partially purified from cell-free extract of the recombinant Escherichia coli carrying a WL-12 mannanase gene by ammonium sulfate fractionation and DEAE-Sepharose column chromatography. Optimal conditions for the partially purified enzyme occurred at pH 6.0 and <TEX>$65^{\circ}C$</TEX>. The enzyme showed higher activity on locust bean gum (LBG) galactomannan and konjac glucomannan than on guar gum galactomannan. The predominant products resulting from the mannanase hydrolysis were mannose, mannobiose and mannotriose for LBG or mannooligosaccharides. The enzyme could hydrolyze mannooligosaccharides larger than mannobiose.
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