국내 사찰에서 제조된 된장으로부터 내열성 ${alpha}$-amylase 생산균으로 분리된 YB-1234는 형태적 특성, 생화학적 성질 및 16S rRNA 유전자 염기서열에 근거하여 Bacillus licheniformis로 동정되었다. B. licheniformis YB-1234의 ${alpha}$-amylase 유전자를 클로닝하여 그 염기서열을 결정하였으며 그로부터 유추된 ${alpha}$-amylase의 아미노산 서열은 glycosyl hydrolase family 13에 속하는 B. licheniformis의 내열성 ${alpha}$-amylases와 매우 높은 상동성을 보였다. ${alpha}$-Aamylase 유전자를 함유한 재조합 대장균과 B. licheniformis에 의해 각각 생산된 ${alpha}$-amylase는 pH 6.0에서 최대활성을 보였으나, 최적 반응온도는 약간의 차이가 있었다. 또한 B. licheniformis로부터 ${alpha}$-amylase는 재조합 대장균에서 생산된 효소보다 열안정성이 매우 높았다. 이들 효소에 의한 maltotetraose와 maltohexaose의 주된 가수분해산물로는 glucose, maltose 및 maltotriose가 관찰되었다.
A bacterial strain was isolated from soybean paste fermented in a Korean Buddhist temple as a producer of the extracellular thermostable ${alpha}$-amylase. The isolate YB-1234 has been identified as Bacillus licheniformis on the basis of its 16S rDNA sequence, morphology and biochemical properties. A gene encoding the thermostable ${alpha}$-amylase of B. licheniformis YB-1234 was cloned into Escherichia coli and its nucleotide sequence was determined. The deduced amino acid sequence of ${alpha}$-amylase was very highly homologous to those of the thermostable ${alpha}$-amylases of B. licheniformis belonging to the glycosyl hydrolase family 13. The ${alpha}$-amylase produced by recombinant E. coli carrying the ${alpha}$-amylase gene exhibited maximal activity at pH 6.0, identical to ${alpha}$-amylase in the culture filtrate of B. licheniformis, while the temperature profile was somewhat different between the two. Particularly, ${alpha}$-amylase produced from B. lcheniformis is much more thermostable than that from recombinant E. coli. The predominant products resulting from the ${alpha}$-amylase hydrolysis were glucose, maltose and maltotriose for maltotetraose and maltohexaose.
