• BMB Reports
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• 제37권3호
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• pp.269-274
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• 2004

DNA polymerases without the 3' exonuclease function ($exo^-$ pol) have been widely used in sequencing and SNP genotyping. As a major player that expedited the coming of the postgenomic era, $exo^-$ polymerases worked remarkably well in the Human Genome Sequencing Project. However, it has become a challenge for this class of polymerases to efficiently screen the large number of SNPs that are found in the human genome. For more than three decades it has been recognized that polymerase fidelity varied according to the presence of proofreading activity that is mediated by its internal 3' exonuclease. Polymerases with proofreading function are famous for their high fidelity in DNA replication both in vivo and in vitro, but this well-known class of polymerases has been almost completely neglected in genetic analysis in the postgenomic era. We speculate that $exo^+$ polymerases may exhibit higher nucleotide identification ability when compared to $exo^-$ polymerases for an in vitro genetic analysis. With the application of $exo^+$ polymerases in SNP assays, a novel mechanism for the maintenance of DNA replication, the on/off switch, was discovered. Two new SNP assays have been developed to carry out genome-wide genotyping, taking advantage of the enzymatic properties of $exo^+$ polymerases. Furthermore, the on/off switch mechanism embodies a powerful nucleotide identification ability, which can be used to discriminate the bases that are upstream of the 3' terminus, and thus defines a new concept in de novo sequencing technology. Application of $exo^+$ polymerases to genetic analysis, and especially SNP assays, will greatly accelerate the pace to personalized medicine.

• Journal of Microbiology and Biotechnology
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• 제14권4호
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• pp.658-664
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• 2004

To find a new utilization of rice bran, nine higher fungi were examined for the production of exo-biopolymer with macrophage stimulating activity from rice bran. Among the exo-biopolymers produced from submerged cultures, Lentinus edodes showed the highest activity, followed by Grifola frondosa, Schizophyllum commune, and Coriolus versicolor. L. edodes also had the most potent macrophage stimulating activity in a liquid culture rather than in a solid culture. In order to improve rice bran utilization and the yield of exo-biopolymer with macrophage stimulating activity, the treatment of Rapidase effectively increased the macrophage stimulating activity (about 30% increase), whereas the other enzymes (Econase, Viscozyme, Ultraflo, Celluclast, and Thermylase) treatments did not increase the macrophage stimulating activity. Exo-biopolymer with macrophage stimulating activity from L. edodes contained mainly neutral sugars (58.7%) with considerable amounts of uronic acid (32.2%) and a small amount of proteins (9.1%). Component sugars of exo-biopolymer consisted of mainly arabinose, galactose, glucose, mannose, and xylose (0.95:0.81:0.96:1.00:0.39, respectively). When the exo-biopolymer was treated with $NaIO_4, NaClO_2$, and pronase, the $NaClO_2$ treatment and pronase digestion had little effect, whereas $NaIO_4$ oxidation significantly decreased the macrophage stimulating activity (47.6% reduction at $100\mug/ml$). Therefore, the carbohydrate moiety in exo-biopolymer from L. edodes plays an important role in the expression of the macrophage stimulating activity.

• Journal of Microbiology and Biotechnology
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• 제15권2호
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• pp.368-375
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• 2005

Batch cultures were carried out to optimize the exo-polysaccharide production by liquid cultures of Pleurotus ferulae. Among the various carbon sources, when $5\%$ of glucose was used, the maximum mycelial growth and exo-polysaccharide concentration reached were 8.78 g/l and 3.59 g/l, respectively. Yeast extract and polypeptone were identified as the most suitable nitrogen sources. In particular, when a mixture of $1\%$ of polypeptone and $0.8\%$ of yeast extract was used, 9.52 g/l of mycelial growth and 4.09 g/l of exo-polysaccharide were obtained. In the case of mineral sources, K$_2$HPO$_4$ and MgSO$_4$$\codt$7H$_2$0 were found to be the best mineral sources for mycelial growth and exo-polysaccharide production. Under the optimized culture conditions, the agitation speed and aeration were investigated for mycelial growth and exo­polysaccharide production in a jar fermentor. The maximum mycelial growth and exo-polysaccharide concentration at 1.5 vvm and 200 rpm obtained were 13.2 g/l and 4.95 g/l, respectively, after 10 days of culture, which were $76\%$ and $79\%$ higher than those of the basal medium. The specific growth rate was decreased with the increase of mycelial growth. However, the specific production rate of the exo-polysaccharide was proportionally increased with the specific growth rate. The proposed model profiles showed good agreement with the experimental results for the mycelial growth and exo-polysaccharide production. The specific production rate using the optimized medium was higher than that of basal medium.

• KSBB Journal
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• 제13권2호
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• pp.162-167
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• 1998

The adsorption behaviors of two major cellulase components, endo I and exo II, from Trichoderma viride were investigated using $\alpha$-celluloses with different correlation crystallinity index(Cc) as substrates. The adsorption of cellulase enzyme components was significantly affected by the reaction condition and the physicochemical properties of the cellulose. The $\alpha$-cellulose was hydrolyzed in the presence of cellulase for various periods. The correlation crystallinity index of $\alpha$-cellulose increased with increasing the hydrolysis time. The adsorption was apparently found to obey the first-order kinetics, and the adsorption activation energy(Ea) was calculated from the adsorption rate constant(ka). The value of adsorption rate constant for endo I was larger than that of exo II. This means that endo I are adsorbed more rapidly than exo II. With the increase in correlation crystallinity index, the values of the adsorption rate constants for endo I and exo II decreased, respectively. The activation energy for the adsorption of exo II on the cellulose also was larger than that of endo I. Also adsorption activation energy of endo I and exo II increased with an increase in the crystallinity of sample cellulose.

• 한국균학회지
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• 제21권2호
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• pp.106-111
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• 1993

사과 겹무늬썩음병균 Botryosphaeria dothidea에 의해 부패된 사과과실에서 pectin질 분해효소를 추출하여 그들의 활성과 pectin 성분의 변화를 조사하였다. 본 병원균은 exo-polygalacturonase(exo-PG), exo-polymethylgalacturonase(exo-PMG), polygalacturonate-trans -e1iminase(PGTE)와 pectinmethyl-trans-eliminase(PMTE)를 생산하였다. 부패된 사과 과육에서 exo-PG와 exo-PMG는 접종 후 7일째 specific activity가 각각 21.15 및 24.65 units/mg protein으로 높게 나타났다. PGTE와 PMTE의 활성은 7일째 각각 5.60과 7.90 uints/mg protein으로 나타났으나 exo-type의 효소보다는 그 활성이 낮았다. 수용성 pectin은 부패가 진행됨에 따라 14일째에 11.50 mg/100 mg-AIS이었고, versene-soluble pectin 역시 7.31 mg/100 mg-AIS로 나타나 건전과와 비교하여 각각 4.23 및 2.16 mg/100 mg-AIS 증가하였다. 부패과의 총 가용성 펙틴 함량은 총 pectin의 72.4%로서 건전과와 비교하여 24.8% 더 높았다. 불용성 pectin 함량은 부패가 진행됨에 따라 15.32 mg/100 mg-AIS에서 7.16 mg/100 mg-AIS로 현저하게 감소하였으며, 총 pectin 함량은 큰 변화가 없었다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.1053-1056
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• 2008

The effects of wall charge and bias voltage on exo-electron emission currents were examined. In addition, the effects of doping elements on the currents were investigated. These results indicated that the statistical delay is inversely proportional to the exo-electron emission currents measured.

• 한국미생물·생명공학회지
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• 제20권5호
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• pp.574-582
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• 1992

Bacillus stearothermophilus exo-xylanase 유전자 DNA가 삽입된 재조합 plasmid pMG1을 가지고 있는 E.coli JM109 exo-xylanase 생산 최적 배양 조건, 생산 효소의 정제 및 정제 효소의 특성 등을 조사 연구하였다. 상기 재조합 E.coli 균주는 0.5 fructose, 0.5 yeast extract, 1.0 tryptone 및 1.0 sodium chloride가 함유된 배지에서 약 10시간 배양했을 때 최대량의 효소를 생산하였으며 생산효소의 94는 세포내에 존재하는 것으로 분석되었다. 생산 효소는 ammonium sulfate 분획, ion exchange chromatography 및 gel filtration 등의 과정을 거쳐 단일 단백질로 정제하였으며 정제 효소는 pH 6.0과 $45^{\circ}C$에서 가장 높은 효소 활성을 나타내었다.또한 1mM $Ca^{2+}$과 $Co^{2+}$ 이온의 첨가는 각각 약 25% 정도의 활성화 효과를 나타내는 반면, 본 효소의 pNPX에 대한 $K_{m}$은 2.75mM, pl값을 4.7, 그리고 분자량은 gel-filtration 법으로는 약 200,000dal., SDS-polyacrylamide gel 전기영동법으로는 약 66,000dal 으로 측정되어 세 개의 동일한 subunit로 구성된 효소 단백질인 것으로 추정되었다. 본 정제 효소는 xylobiose, xylotrioxe 및 xylotetraose 등의 xylo-oligosaccharide를 효과적으로 분해함은 물론이고, 분해율은 낮으나 birchwood xylan, larchwood xylan 및 oatspelt xylan 등의 xyland에도 작용, xylose 생산을 확인함으로써 본 효소는 그 예가 극히 드문 bacterial exo-xylanase인 것으로 분류되었다.

• 한국구조물진단유지관리공학회 논문집
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• 제19권5호
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• pp.38-44
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• 2015

본 논문에서는 효과적인 제진설계를 구현하기 위한 설계기술 개발의 일환으로 최근 제안된 Exo-type 감쇠시스템을 활용하여 15층과 20층의 연구 대상 건물을 대상으로 감쇠시스템의 최적 강성비와 적용된 감쇠장치의 최적 항복비에 따른 철근콘크리트 라멘조 건물의 제진 효과를 검토해 보았다. 해석결과, Exo-type 감쇠시스템을 3개층 적용 시에는 대상 건물 15층과 20층 모두 밑면전단력과 최상층 최대응답변위 감소라는 관점에서 유효한 제진효과를 얻기 위해서는 Exo-type 감쇠시스템과 대상 건물의 강성비는 7.0 이상 확보를 하여야 하며, 감쇠시스템에 적용된 감쇠장치의 항복비는 대상 건물의 층전단력의 약 8.0% 이상 확보할 필요가 있는 것으로 나타났다. 또한, Exo-type 감쇠시스템을 5개 층 적용 시에는 대상 건물 15층과 20층 모두 Exo-type 감쇠시스템과 대상 건물의 강성비는 2.5 이상 확보 하여야 하며, 감쇠시스템에 적용된 감쇠장치의 대상 건물의 층전단력의 약 3.5%이상 확보할 필요가 있는 것으로 나타났다.

• Journal of Microbiology and Biotechnology
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• 제28권10호
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• pp.1671-1682
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• 2018

Alginate lyases (endo and exo-lyases) are required for the degradation of alginate into its constituting monomers. Efficient bioethanol production and extraction of bioactives from brown algae requires intensive use of these enzymes. Nonetheless, there are few commercial alginate lyase preparations, and their costs make them unsuitable for large scale experiments. A recombinant expression protocol has been developed in this study for producing seven endo-lyases and three exo-lyases as soluble and highly active preparations. Saccharification of alginate using 21 different endo/exo-lyase combinations shows that there is complementary enzymatic activity between some of the endo/exo pairs. This is probably due to favorable matching of their substrate biases for the different glycosidic bonds in the alginate molecule. Therefore, selection of enzymes for the best saccharification results for a given biomass should be based on screens comprising both types of lyases. Additionally, different incubation temperatures, enzyme load ratios, and enzyme loading strategies were assessed using the best four enzyme combinations for treating Macrocystis pyrifera biomass. It was shown that $30^{\circ}C$ with a 1:3 endo/exo loading ratio was suitable for all four combinations. Moreover, simultaneous loading of endo-and exo-lyases at the beginning of the reaction allowed maximum alginate saccharification in half the time than when the exo-lyases were added sequentially.

• Molecules and Cells
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• 제37권5호
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• pp.412-417
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• 2014

It has been reported that exogenously introduced micro-RNA (exo-miRNA) competes with endogenously expressed miRNAs (endo-miRNAs) in human cells, resulting in a detectable upregulation of mRNAs with endo-miRNA target sites (TSs). However, the detailed mechanisms of the competition between exo- and endo-miRNAs remain uninvestigated. In this study, using 74 microarrays that monitored the whole-transcriptome response after introducing miRNAs or siRNAs into HeLa cells, we systematically examined the derepression of mRNAs with exo- and/or endo-miRNA TSs. We quantitatively assessed the effect of the number of endo-miRNA TSs on the degree of mRNA derepression. As a result, we observed that the number of endo-miRNA TSs was significantly associated with the degree of derepression, supporting that the derepression resulted from the competition between exo- and endo-miRNAs. However, when we examined whether the site proficiency of exo-miRNA TSs could also influence mRNA derepression, to our surprise, we discovered a strong positive correlation. Our analysis indicates that site proficiencies of both exo- and endo-miRNA TSs are important determinants for the degree of mRNA derepression, implying that the derepression of mRNAs in response to exo-miRNA is more complex than that currently perceived. Our observations may lead to a more complete understanding of the detailed mechanisms of the competition between exo- and endo-miRNAs and to a more accurate prediction of miRNA targets. Our analysis also suggests an interesting hypothesis that long 3'-UTRs may function as molecular buffer against gene expression regulation by individual miRNAs.