• Journal of Microbiology and Biotechnology
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• 제27권12호
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• pp.2180-2189
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• 2017

Psychrophilic phytases suitable for aquaculture are rare. In this study, a phytase of the histidine acid phosphatase (HAP) family was identified in Morchella importuna, a psychrophilic mushroom. The phytase showed 38% identity with Aspergillus niger PhyB, which was the closest hit. The M. importuna phytase was overexpressed in Pichia pastoris, purified, and characterized. The phytase had an optimum temperature at $25^{\circ}C$, which is the lowest among all the known phytases to our best knowledge. The optimum pH (6.5) is higher than most of the known HAP phytases, which is fit for the weak acidic condition in fish gut. At the optimum pH and temperature, MiPhyA showed the maximum activity level ($2,384.6{\pm}90.4{\mu}mol{\cdot}min^{-1}{\cdot}mg^{-1}$, suggesting that the enzyme possesses a higher activity level over many known phytases at low temperatures. The phytate-degrading efficacy was tested on three common feed materials (soybean meal/rapeseed meal/corn meal) and was compared with the well-known phytases of Escherichia coli and A. niger. When using the same amount of activity units, MiPhyA could yield at least $3{\times}$ more inorganic phosphate than the two reference phytases. When using the same weight of protein, MiPhyA could yield at least $5{\times}$ more inorganic phosphate than the other two. Since it could degrade phytate in feed materials efficiently under low temperature and weak acidic conditions, which are common for aquacultural application, MiPhyA might be a promising candidate as a feed additive enzyme.

• 한국미생물·생명공학회지
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• 제38권2호
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• pp.151-157
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• 2010

보리 맥아로부터 발견된 서로 다른 알파아밀라제 동질효소(AMY1, AMY2)는 80%에 달하는 높은 아미노산 서열의 상동성을 보이지만, 효소적 특성은 서로 매우 다르다. 따라서 본 연구에서는 staggered extension process(StEP) 기술을 이용하여 AMY1과 AMY2 유전자가 조합된 5종의 chimera 효소를 제조하고, 각각의 특성을 비교하여 총 8개 부위(I~VIII)의 영향을 확인하였다. 결과적으로, AMY-D2, D8, E12 chimera 효소의 경우, AMY1과 AMY2의 중간적 칼슘의존성을 보였으며, BASI(barley $\alpha$-amylase/subtilisin inhibitor) 단백질에 의한 저해효과는 AMY-E10 효소에서만 관찰되었다. 한편 AMY-C6의 경우, AMY1과 유사한 효소특성을 보였으며, AMY-E10은 AMY2 형태의 칼슘의존성을 나타내었다. 따라서 보리 아밀라제의 제 II, III, IV부위가 BASI와의 상호작용에 중요한 역할을 담당하며, 제 III, V, VI, VII부위는 칼슘의존성에 부분적인 영향을 미치는 것으로 판단하였다.