• Korean Journal of Microbiology
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• v.48 no.1
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• pp.1-7
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• 2012

This study explores the interaction between the production of indole-3-acetic acid (IAA), a typical phytohormone auxin and the role of IAA biosynthetic pathways in each IAA producing rhizobacterial strain. The bacterial strains were isolated from rhizosphere of wild plants and identified as Acinetobacter guillouiae SW5, Bacillus thuringiensis SW17, Rhodococcus equi SW9, and Lysinibacillus fusiformis SW13. A. guillouiae SW5 exhibited the highest production of IAA using tryptophan-dependent pathways among the 4 strains. When indole-3-acetamide (IAM) was added, Rhodococcus equi SW9 showed the highest IAA production of $3824{\mu}g/mg$ protein using amidase activity. A. guillouiae SW5 also showed the highest production of IAA using two pathways with indole-3-acetonitrile (IAN), and its nitrile hydratase activity might be higher than nitrilase. B. thuringiensis SW17 showed the lowest IAA production, and most of IAA might be produced by the amidase activity, although the nitrilase activity was the highest among 4 strains. The roles of nitrile converting enzymes were relatively similar in IAA synthesis by Lysinibacillus fusiformis SW13. Tryptophan-independent pathway of IAA production was utilized by only A. guillouiae SW5.

• Journal of Microbiology and Biotechnology
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• v.18 no.3
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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.