• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2001.06a
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• pp.179-182
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• 2001

Two intracellular enzymes, cellobiose phosphorylase (CBP) and cellodextrin phosphorylase (CDP) are involved in the phosphorolytic pathway in cellulose degradation. Those enzymes are considered to be useful in syntheses of oligosaccharides because the reactions are reversible. CBP from Cellvibrio gilvus and CDP from Clostridium thermocellum YM-4 were cloned and over-expressed in Escharichia coli. Both the enzyme reactions showed ordered bi bi mechanism. Acceptor specificity of CBP in the reverse reaction was determined. Several $\beta$-l,4-glucosyl disaccharides were synthesized by using the reaction. A new substrate inhibition pattern, competitive substrate inhibition, was also found in the reverse reaction of CBP Cellobiose was produced from sucrose at a high yield by a combined action of three enzymes including CBP

• BMB Reports
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• v.28 no.6
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• pp.533-537
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• 1995

The detection with lucigenin under physiological conditions is selective for ${\cdot} O_{2}^{-}$, for it can be accepted that lucigenin indicates actual intramembranal $\cdot O_{2}^{-}- formation$. Lucigenin chemiluminescence (CL) was elicited from the plasma membrane (PM) only by addition of reduced pyridine nucleotide. NADPH was preferred to NADH in PM and hepatocytes. This specificity was masked by $NAD(P)^+$ inhibition. The half maximum rate of CL increase was obtained with 1.5 ${\mu}m$ NADH or 55 ${\mu}m$ NADPH in hepatocytes and 6 ${\mu}m$ NADH or 30 ${\mu}m$ NADPH in plasma membranes. Measurement of these NADPH values required the presence of a NADPH-regenerating system. With NADPH the maximal rate obtained was 10 fold higher than with NADH. NADPH and NADH could produce CL when having access from either side of the membrane. They seemed to react with the identical acceptor because NADH-induced CL was also inhibited by $NADP^+$. The characteristics of ${\cdot}O_{2}^{-}-formation$ produced by pyridine nucleotide will be discussed.

• YAKHAK HOEJI
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• v.42 no.1
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• pp.53-58
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• 1998

A novel type of sulfotransferase, arylsulfate sulfotransferase (EC 2.8.2.22) purified from Haemophilus K-12, an intestinal bacterium of a mouse, was immobilized onto AH-S epharose 4B, CH-Sepharose 4B and DEAE-celluose. The enzyme was stabilized for storage more markedly by covalent immobilization onto AH-Spharose 4B or CH-Sepharose 4B and by adsorptive immobilization onto DEAE-cellulose than the free enzyme. The optimal pH and acceptor substrate specificity of immobuized enzyme were similar to those of the free enzyme.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.579-582
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• 2000

(R,S)-3-amino-n-butanoic acid$(DL-\;{\beta}\;-homoalanine)$ has been kinetically resolved using Alcaligenes denitrificans Y2k-2 as a biocatalyst, which was isolated from soil by enrichment culture, which was carried out with minimal media containing (R,S)-3-amino-n-butanoic acid as a sole nitrogen source. The enzyme which peformed this kinetic resolution assumed to belong to the ${\omega}-transaminase$ family, because A. denitrificans used pyruvate as amino acceptor and its transaminase activity was inhibited by gabaculine, aminooxy acetic acid and hydroxylamine. In whole cell reaction, (R,S)-3-amino-n-butanoic acid was kinetically resolved to the corresponding (R)-3-amino-n-butanoic acid with excellent E (>100) in the presence of pyruvate as an amino acceptor at $37^{\circ}C$. (S-specific) We observed the substrate inhibition for pyruvate at 100mM. In this study, characteristics of transaminase activity of Alcaligenes denitrificans Y2k-2, such as substrate specificity and thermostability, are carried out for the development of (R)-3- amino-n-butanoic acid production system.

• Journal of Microbiology and Biotechnology
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• v.22 no.10
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• pp.1395-1400
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• 2012

In this study, we investigated various cultural and operational factors to enhance electricity generation in a microbial fuel cell (MFC) using Geobacter sulfurreducens. The pure culture of G. sulfurreducens was cultivated using various substrates including acetate, malate, succinate, and butyrate, with fumarate as an electron acceptor. Cell growth was observed only in acetate-fed medium, when the cell concentrations increased 4-fold for 3 days. A high acetate concentration suppressed electricity generation. As the acetate concentration was increased from 5 to 20 mM, the power density dropped from 16 to $13mW/m^2$, whereas the coulombic efficiency (CE) declined by about half. The immobilization of G. sulfurreducens on the anode considerably reduced the enrichment period from 15 to 7 days. Using argon gas to create an anaerobic condition in the anode chamber led to increased pH, and electricity generation subsequently dropped. When the plain carbon paper cathode was replaced by Pt-coated carbon paper (0.5 mg $Pt/cm^2$), the CE increased greatly from 39% to 83%.

• Journal of Microbiology and Biotechnology
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• v.18 no.5
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• pp.859-865
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• 2008

Bacterial glycosyltransferases have drawn growing attention as economical enzymes for oligosaccharide synthesis, with their easy expression and relatively broad substrate specificity. Here, we characterized a glycosyltransferase homolog (Fnu_GT) from a human oral pathogen, Fusobacterium nucleatum. Bioinformatic analysis showed that Fnu_GT belongs to the glycosyltransferases family II. The recombinant Fnu_GT (rFnu_GT) expressed in Escherichia coli displayed the highest glycosylation activity when UDP-galactose (Gal) was used as a donor nucleotide-sugar with heptose or N-acetylglucosamine (GlcNAc) as an acceptor sugar. Interestingly, rFnu_GT transferred the galactose moiety of UDP-Gal to a nonreducing terminal GlcNAc attached to the trimannosyl core glycan, indicating its potential as an enzyme for human-type N-glycan synthesis.

• BMB Reports
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• v.39 no.1
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• pp.46-54
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• 2006

The coenzyme A-acylating 2-oxoacid:ferredoxin oxidoreductase and ferredoxin (an effective electron acceptor) were purified from the hyperthermophilic archaeon, Sulfolobus solfataricus P1 (DSM1616). The purified ferredoxin is a monomeric protein with an apparent molecular mass of approximately 11 kDa by SDS-PAGE and of $11,180{\pm}50$ Da by MALDI-TOF mass spectrometry. Ferredoxin was identified to be a dicluster, [3Fe-4S][4Fe-4S], type ferredoxin by spectrophotometric and EPR studies, and appeared to be zinc-containing based on the shared homology of its N-terminal sequence with those of known zinc-containing ferredoxins. On the other hand, the purified 2-oxoacid: ferredoxin oxidoreductase was found to be a heterodimeric enzyme consisting of 69 kDa $\alpha$ and 34 kDa $\beta$ subunits by SDS-PAGE and MALDI-TOF mass spectrometry. The purified enzyme showed a specific activity of 52.6 units/mg for the reduction of cytochrome c with 2-oxoglutarate as substrate at $55^{\circ}C$, pH 7.0. Maximum activity was observed at $70^{\circ}C$ and the optimum pH for enzymatic activity was 7.0 -8.0. The enzyme displays broad substrate specificity toward 2-oxoacids, such as pyruvate, 2-oxobutyrate, and 2-oxoglutarate. Among the 2-oxoacids tested (pyruvate, 2-oxobutyrate, and 2-oxoglutarate), 2-oxoglutarate was found to be the best substrate with $K_m$ and $k_{cat}$ values of $163\;{\mu}M$ and $452\;min^{-1}$, respectively. These results provide useful information for structural studies on these two proteins and for studies on the mechanism of electron transfer between the two.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2004.06a
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• pp.215-218
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• 2004

Dextrans make up a class of polysaccharides that are D-glucans of various structures with contiguous $\alpha$-1longrightarrow6 ~6 glycosidic linkages in the main chains and $\alpha$-1longrightarrow2, $\alpha$-1longrightarrow3, or $\alpha$-1longrightarrow4 branch glycosidic linkages, depending on the specificity of the particular dextransucrase. Glucansucrases that catalyze glucans synthesis from sucrose. When other carbohydrates, in addition to sucrose, are present in the enzyme digest, the enzyme transfers glucose to the carbohydrate acceptors in the secondary reaction that diverts some of the glucose from incorporation into glucan. Many carbohydrate acceptors have been recognized and the products that result are dependent on the particular enzyme and the structure of the particular acceptor. Because of these unique catalytic characteristics, various dextransucrases have many important industrial and medical uses. To improve the understanding of their action mode and extend their applications, this study describes mechanism of glucan synthesis and potential industrial uses of dextransucrases, and our recent findings on the structural, functional organization and directed evolution of the glucansucrases to offer for designing glucansucrases with improved properties.

• Journal of the Korean Society of Food Science and Nutrition
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• v.29 no.1
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• pp.41-48
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• 2000

A bacterial strain, designated as JK-43, producing extracellular cyclodextrin glucanotransferase (CGTase)[EC 2.4.1.19] was isolated from kimchi. The CGTase from isolated strain JK-43 showed the transglucosylation activity from soluble starch to L-ascorbic acid(AA) compared to those obtained from other strains. A main product formed by this reaction was identified as $2-O-{\alpha}-glucopyranosyl$ L-ascorbic acid(AA-2G) by testing its susceptibility to ${\alpha}-glucosidase$ hydrolysis, the HPLC profiles, and through the elementary analysis. the ${\beta}-CD,\;{\gamma}-CD$, potato starch and corn starch were identified to be suitable glucosyl donor for transglucosylation reaction on AA by CGTase. Acceptor specificity on AA-2G production was examined by use of AA, Iso-AA and AA-2P. Transglucosylation was observed toward AA-2P as well as AA and Iso-AA. The microorganism isolated from kimchi was identified as a strain of Bacillus sp. JK-43 based on the morphological, cultural, biochemical characteristics and partial 16SrDNA sequence analysis. The maximal CGTase production was observed in a medium containing 1.0% soluble starch, 1.0% yeast extract, 1.0% $Na_2CO_3\;0.1%\;K_2HPO_4,\;and\;0.02%\;MgSO_4{\cdot}7H_2O$ with initial pH 7.0. The strain was cultured at $37^{\circ}C$ for 26 hrs with reciprocal shaking.