• Applied Chemistry for Engineering
• /
• v.18 no.3
• /
• pp.279-283
• /
• 2007

Epoxide hydrolase (EH) gene of Caulobacter crescentus was cloned by PCR and expressed in Escherichia coli. The C. crescentus EH (CcEH) primarily attacked at the benzylic carbon of (S)-styrene oxide, while the CcEH preferentially attacked at the terminal carbon of (R)-styrene oxide, thus leading to the formation of (R)-phenyl-1,2-ethanediol as the main product. (R)-phenyl-1,2-ethanediol was obtained with 85% enantiomeric excess and yield of 69% from racemic styrene oxide via enantioconvergent hydrolysis by using recombinant CcEH as the single biocatalyst.

• Korean Chemical Engineering Research
• /
• v.47 no.5
• /
• pp.624-629
• /
• 2009

It is the most important step to screen soluble and insoluble proteins when we attempt to improve the solubility of recombinant proteins through directed evolution approach. Here we show that the solubility of a recombinant protein in vivo can be examined by expressing the recombinant protein with beta-lactamase as a fusion partner. First we constructed an expression system which can produc a fusion protein with the C-terminal of beta-lactamase. Two soluble proteins, i.e. adenine deaminase and aspartate aminotransferase, and insoluble GlcNAc-2-epimerase were cloned into the developed expression vector, respectively. We investigated the effect of the expression of the three recombinant fusion proteins on the growth of E. coli, and confirmed that the solubilities of the recombinant proteins correlated with cell growth rates.

• KSBB Journal
• /
• v.27 no.4
• /
• pp.257-262
• /
• 2012

The gene encoding Thermus thermophilus HJ6 laccase (Tt-laccase) was cloned, sequenced, and comprised of 1,389 nucleotides encoding a protein (462 amino acids) with a predicted molecular mass of 51,049 Da. The deduced amino acid sequence of Tt-laccase showed 99.7% and 44.3% identities to the Thermus thermophilus HB27 laccase and Synechococcus sp. RS9917 laccase, respectively. Tt-laccase gene was expressed as a fusion protein with six histidine residues in E. coli Rosetta-gami (DE3) cells, and the recombinant protein was purified to homogeneity. UV-Vis spectrum analysis revealed that the enzyme has copper atoms, a type I Cu(II) and a type III binuclear Cu(II). The optimum pH for the oxidation of guaiacol was 5.0 and the optimum temperature was $90^{\circ}C$ The half-life of heat inactivation was about 120 min at $90^{\circ}C$ The enzyme reaction was inhibited by sodium azide, L-cystein, EDTA, dithiothreitol, tropolone, and kojic acid. The enzyme oxidized various known laccase substrates, its lowest $K_m$ value being for 4-hydroxyindole, highest $k_{cat}$ value for syringaldazine, and highest $k_{cat}/K_m$ for guaiacol.

• Journal of Dairy Science and Biotechnology
• /
• v.29 no.1
• /
• pp.49-54
• /
• 2011

Bile salt hydrolase (BSH, EC 3.5.1.24) activity, which cleaves amide bond between carboxyl group (bile acid) and amino group (glycine or taurine), is commonly detected in gut-associated species of human and animal. During the screening of BSH active strains from the fecal samples of elderly human volunteers, strain CU30-2 was isolated on the basis of the highly active BSH producing activity. A bsh gene of the isolate was cloned into the pET22b expression vector and overexpressed in Escherichia coli BL21 (DE3) Gold by induction with 1mM IPTG. The overexpressed BSH enzyme with 6x His-tag was purified with apparent homogeneity using a $Ni^+$-NTA agarose column and characterized. The BSH enzyme of E. faecalis CU30-2 exhibited approximately 50 times higher activity against glycol-conjugated bile salts than tauro-conjugated bile salts having the highest activity against glycocholic acid. Considering the prevalence of E. faecalis strains in the human GI tract and glycol-conjugates dominated bile acid composition of human bile, further study is needed to investigate the impact of the BSH activity exerted by E. faecalis strains to the host as well as to the BSH producing strains.

• Korean Journal of Microbiology
• /
• v.31 no.2
• /
• pp.123-128
• /
• 1993

Genes for dinitrogenase reductase (nifH) and dinitogenase a subunit (nifD) were found to be located on 7.9 kb of EcoRI, 6.5 kb of Sail, 7.3 kb of HindlII and 4.4 kb of Pstl fragments of the genomic blot of Rhizobium sp. SNU003. a symbiotic strain from root nodule of Canavalia lineata. Nine recombinant phage nif-clones were selected from the genomic library constructed by using EMBL-3 BamHI arms of bacteriophage lambda. Among them. Rnif-6 had insert DNA of 15.3 kb. in which 7.6 kb of BamHI!SacI fragment contained nifHD region. Therefore, the 7.6 kb fragment was subcloned into pUC19 and partial restriction map was constructed. As the results, nifH and nifD were found to be located continuously on 4.5 kb of BamHI/BglIl in the genome of Rhizobium sp. SNU003 strain.

• Microbiology and Biotechnology Letters
• /
• v.46 no.1
• /
• pp.51-58
• /
• 2018

The expression, purification, and characterization of cold-adapted lipase from the psychrophile, Janthinobacterium sp. were investigated. The gene encoding lipase from Janthinobacterium sp. PAMC 25641 was cloned into a pET28a(+) vector and heterologously expressed in Escherichia coli BL21 (DE3). The amino acid sequence deduced from the nucleotide sequence (930 bp) corresponded to a protein having 309 amino acid residues with a molecular weight of 32.7 kDa and a pI of 5.55. Recombinant E. coli harboring the Janthinobacterium lipase gene were induced by addition of isopropyl-${\beta}$-D-thiogalactopyranoside. $Ni^{2+}$-NTA affinity chromatography was used to purify the lipase, which had a specific activity of 107.9 U/mg protein. The effect of temperature and pH on the activity of lipase was measured using p-nitrophenyl octanoate as a substrate. The stability of the lipase at low temperatures indicated it is a cold-adapted enzyme. The lipase activity was increased by $Na^{2+}$, $Mg^{2+}$, and $Mn^{2+}$, and decreased by $Zn^{2+}$ and $Co^{2+}$. Analysis of the lipase activity using various p-nitrophenyl esters showed a strong preference toward short acyl chains of the esters, indicating the ability of the cold-adapted lipase to hydrolyze short-chain esters.

• Applied Biological Chemistry
• /
• v.45 no.4
• /
• pp.190-194
• /
• 2002

Expression of Bacillus subtilis glutamyl-tRNA synthetase (GluRS) in Escherichia coli is lethal for the host, probably because this enzyme misaminoacylates ${tRNA_l}^{Gln}$ with glutamate in vivo. In order to overexpress B. subtilis GluRS, encoded by the gltX gene, in E. coli, this gene was amplified from B. subtilis 168 chromosomal DNA using PCR method and the entire coding region was cloned into a pET11a expression vector so that it was expressed under the control or the T7 Promoter. The resulting recombinant pEBER plasmid was transformed into E. coli Novablue (DE3) bearing the T7 RNA polymerase gene for expression. After IPTG treatment, the overproduced enzyme was purified using ammonium sulfate fractionation, Source Q anion exchange chromatography, Superdex-200 gel filtration, and Mono Q anion exchange chromatography. The purified enzyme yielded 18-fold increase in specific activity over the crude cell extract and its molecular weight was approximately 55 kDa on SDS-PAGE.

• Microbiology and Biotechnology Letters
• /
• v.34 no.4
• /
• pp.318-322
• /
• 2006

The intracellular invertase gene of alkalophilic and thermophilic Bacillus sp. TA-11 which was isolated from compost was cloned and expressed in E. coil HB101 using pUC19 as a vector. The invertase of the recombinant E. coli (pYC 17) was maximally produced when it was incubated at 37$^{\circ}C$ for 9 h in a SY medium containing 0.25% sucrose, 0.5% yeast extract, 0.1% each of $K_2HPO_4$ and $KH_2PO_4$, with an initial pH of 8.0. The final enzyme activity under the above condition was 47.7 U per ml of cell-free extract.

• Microbiology and Biotechnology Letters
• /
• v.35 no.4
• /
• pp.352-356
• /
• 2007

A Lactobacillus sp. has been isolated from infant feces and characterized according to its physiological properties and identified as Lactobacillus acidophilus KLA1012. A gene coding surface layer protein (SLP) has been cloned and the sequence has been determined. The nucleotide sequence of slpA was 1,338 bp in size and was identical to that of L. acidophilus ATCC 4356 (100%). Amino acid sequence of SLP-A was deduced from the nucleotide sequence and it had signal sequence at N-terminal, consisting of positively charged amino acid mainly lysine. slpA was cloned and heterologously expressed in E. coli M15 and the 45.2 kDa surface-layer protein band was examined by SDS-PAGE and confirmed by Western blotting using polyclonal antibody against L. acidophilus KLA 1012 SLP-A protein.

• KSBB Journal
• /
• v.28 no.5
• /
• pp.332-337
• /
• 2013

The gene encoding for xylose isomerase from the thermophilic bacterium Thermotoga maritima was cloned and recombinantly expressed in E. coli cells. Optimal activity was shown at $90^{\circ}C$ and pH 8.0. Treatment of saponin by recombinant xylose isomerase increased the growth inhibitory effect against human gastric cancer (AGS) cells and human colon cancer (HT-29) cells. On the other hand, treatment of fucoidan by the enzyme could not change the growth inhibitory effect against the same cancer cells. One ${\mu}g/ml$ of enzyme-treated saponin exhibited the same or higher growth inhibitory effect against both cancer cells compared with 100 ${\mu}g/ml$ of enzymeuntreated saponin. These results would be useful in the development of functional food or drug.