• 미생물학회지
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• 제48권1호
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• pp.1-7
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• 2012

대표적인 식물호르몬인 indole-acetic acid (IAA)를 생성하는 근권세균에서 IAA 생합성 경로와 생성량과의 관계를 파악하기 위해 IAA 생성능이 크게 다른 4개 균주를 선발하고 동정하였다. 특정 경로를 이용한 IAA 생합성능의 조사를 위해 주요 전구물질을 첨가하여 IAA 생성량을 측정하였다. Tryptophan 의존적 경로에 의한 총 IAA 생성량은 Acinetobacter guillouiae SW5가 1.66 mg/ml로 가장 높았으며, indole acetamide (IAM)를 배지에 첨가했을 때 amidase의 활성은 분리균주 중 Rhodococcus equi SW9이 가장 높았다. IAA 생합성을 위한 또 다른 두 가지 경로의 전구물질인 indole acetonitrile (IAN)을 첨가하였을 때 IAA 생합성은 A. guillouiae SW5가 가장 높았으며, 이 때 nitrilase 보다는 nitrile hydratase의 활성이 높았다. 그러나 두 경로 중 IAN을 직접 IAA로 전환시키는 nitrilase의 활성은 Bacillus thuringiensis SW17이 균주들 중 가장 높았다. B. thuringiensis SW17은 4균주 중 IAA생합성능이 가장 낮았으며 tryptophan을 이용하여 생합성하는 IAA 중 상당량을 IAM을 거치는 경로를 통해 생성한다. Lysinibacillus fusiformis SW13은 IAA 생합성에 관여하는 nitrile 전환경로들을 비교적 고르게 이용하여 IAA를 생성하였다. Tryptophan 비의존적 경로를 통한 IAA 생합성은 A. guillouiae SW5에서만 소량 관찰되었다.

• Journal of Microbiology and Biotechnology
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• 제18권3호
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• pp.552-559
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• 2008

Ethyl (S)-4-chloro-3-hydroxybutyrate is an intermediate for the synthesis of Atorvastatin, a chiral drug used for hypercholesterolemia. A Rhodococcus erythropolisstrain (No.7) able to convert 4-chloro-3-hydroxybutyronitrile into 4-chloro-3-hydroxybutyric acid has recently been isolated from soil. This activity has been regarded as having been caused by the successive actions of the nitrile hydratase and amidase. In this instance, the corresponding amidase gene was cloned from the R. erythropolis strain and expressed in Escherichia coli cells. A soluble active form of amidase enzyme was obtained at $18^{\circ}C$. The Ni column-purified recombinant amidase was found to have a specific activity of 3.89 U/mg toward the substrate isobutyramide. The amidase was found to exhibit a higher degree of activity when used with mid-chain substrates than with short-chain ones. Put differently, amongst the various amides tested, isobutyramide and butyramide were found to be hydrolyzed the most rapidly. In addition to amidase activity, the enzyme was found to exhibit acyltransferase activity when hydroxyl amine was present. This dual activity has also been observed in other enzymes belonging to the same amidase group (E.C. 3.5.1.4). Moreover, the purified enzyme was proven to be able to enantioselectively hydrolyze 4-chloro-3-hydroxybutyramide into the corresponding acid. The e.e. value was measured to be 52% when the conversion yield was 57%. Although this e.e. value is low for direct commercial use, molecular evolution could eventually result in this amidase being used as a biocatalyst for the production of ethyl (S)-4-chloro-3-hydroxybutyrate.