• Bulletin of the Korean Chemical Society
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• 제14권1호
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• pp.32-38
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• 1993

3-(3-Bromotetrahydrofuran-2-yl)-3-cephem 7 was obtained from 3-(2-hydroxyethyl)vinyl-3-cephem 6 by the cyclization reaction using N-bromosuccinimide. Compound 5 was prepared by Wittig reaction, namely a coupling of cephem-derived triphenylphosphonium salt 3 with aldehyde component 4 in the presence of base.

• Bulletin of the Korean Chemical Society
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• 제28권5호
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• pp.751-757
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• 2007

To develop new COX-2 inhibitors, 1,5-diarylhydantoins and 1,5-diaryl-2-thiohydantoins were synthesized from phenylacetic acids by esterification, bromination, C-N bond formation and cyclization. Esters 1-3 were efficiently synthesized from the starting materials by reflux in absolute methanol for 3 h containing concentrated sulfuric acid as catalyst. Bromination was carried out with N-bromosuccinimide at rt in dichloromethane. Bromides 4-6 were reacted with aniline, p-anisidine, sulfanilamide in ethanol (or N,N-dimethylformamide) to provide the amines 7-15. Hydantoins and 2-thiohydantoins 16-46 were synthesized from amines 7-15 by treating them with potassium isocyanate (or potassium thiocyanate) and triethylamine. The synthetic process from alkyl α-anilinophenylacetate 7-15 to 3-alkylhydantoins was carried out in a one-pot reaction using alkyl isocyanate (alkyl isothiocyanate).

• 생명과학회지
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• 제8권5호
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• pp.497-503
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• 1998

GTase와 CDase를 함께 분비$\cdot$생산하는 B. stearother-mophilus KJl6 균주의 CDase를 ammonium sulfate 침전, DBAE-cellulose, Sephadex G-100 column chromatogra-phy, 및 FPLC로 수율 7%, 비활성 12.4 units/mg, 정제도 87.6배로 정제된 CDase를 얻었으며 SDS-PAGE 상 단일 band를 확인하였다. 정제된 CDase의 분자량은 약 68,000 dalton 이었고 활성 최적 pH와 온도는 6.0와 55$^{\circ}C$였다. pH 안정성은 5.5~8.5의 범위에서 비교적 안정하였으며, 온도 안정성은 5$0^{\circ}C$에서 2시간까지는 안정하였고, 7$0^{\circ}C$에서 1시간 전처리하여도 80% 이상의 잔존활성을 나타내었다. 효소 활성은 $Cu^{+2}$와 $Hg^{+2}$와 같은 금속이온과 p-chlorome-rcuribenzoate, N-bromosuccinimide, mercaptoethanol, dithiothreitol에 의해서 효소활성이 강하게 저해되었다. 기질에 대한 반응 특이성은 $\gamma$ -CD를 가장 잘 분해하였으며, 그 외에 soluble starch나 amylose, amylopectin 등의 기질도 잘 분해하나 이들의 분해속도는 $\gamma$-CD에 비해서는 늦었다. 이들 기질의 최종 분해산물은 maltose였으며, maltose는 거의 분해되지 않았다.

• 한국균학회지
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• 제24권4호통권79호
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• pp.255-264
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• 1996

호알카리성 진균 Cephalosporium sp. RYM-202가 생산하는 alkaline xylanase (CX-III)의 작용에 의해 xylan 기질로부터 생성되는 주요 가수분해 산물은 xylobiose와 중합도가 4이상인 xylooligosaccharides이었다. 이 효소는 xylobiose에 대한 분해능을 가지고 있지 않지만 xylotriose로부터는 xylobiose를, xlyotetraose로부터 xylobiose와 xylotriose를 주산물로 형성하였다. 이러한 결과들은 CX-III가 transglycosidase 활성을 소유하는 전형적인 endo-type xylanase임을 보여준다. N-bromosuccinimide에 의한 CX-III의 화학적 변환 실험결과 효소 1분자 당 2개의 tryptophan 잔기가 활성에 관여하는 것으로 나타났다. 그러나 iodoacetamide 및 diethylpyrocarbonate에 의한 효소활성의 저해효과는 나타나지 않음으로써 이 효소의 활성부위에 cysteine과 histidine 잔기가 필수적이지 않음이 확인되었다.

• 미생물학회지
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• 제32권4호
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• pp.306-314
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• 1994

Xylan과 관련 다당류 (xylotriose, xylotetraose, arabinoxylotriose)에 대한 Trichoderma koningii ATCC 26113에서 분리된 xylanase II의 작용양상은 xylanase II가 endo-enzyme이고 transxylosidation의 활성을 가지고 있다고 보여진다. Xylanase II에 의해 형성된 반응산물을 $^1HNMR$ 분광법으로 분석한 결과는 본 효소에 의해 얻어진 xylooligosaccharides의 가수분해산물은 모두가 ${\beta}$-1,4-xylosidic linkage만을 가지고 있는 것으로 판명되었다. 본 효소를 iodoacetamide로 화학적으로 변형시켰을 때 효소 mole당 cysteine 잔기가 두 개가 활성에 필요한 것으로 보여졌으며, N-bromosuccinimide 로 처리하였을 때는 활성부위에 tryptophan 잔기가 여덟 개 존재하는 것으로 판명되었다.

• Archives of Pharmacal Research
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• 제16권2호
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• pp.158-160
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• 1993

2-Oxazolidinones and 1,3-oxazine-2-ones, key moieties of new antiulcer agents, were prepared successfully by treating corresponding hydroxyamide with N-bromosuccinimide (NBS) and silveracetate in acetonitrile. From the fact that the methods for the preparation of hydoxy amides are versatile and such amides could be converted to the corresponding 2-oxazolid-iones and 1,3-oxazine-2-one under our reaction condition, we think that our method is very practical one for the preparation of such compounds. In addition, the above synthetic example affords a good evidence of the synthetic applicability of our improved Hofmann rearrangement.

• 한국미생물·생명공학회지
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• 제22권6호
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• pp.636-642
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• 1994

Essential amino acids involving in the catalytic mechanism of the $\beta$-D-xylosidase of Bacillus stearothermophilus were determined by chemical modification studies. Among various che- mical modifiers tested N-bromosuccinimide (NBS), $\rho$-hydroxymercurybenzoate (PHMB), N-ethylma- leimide, 1-[3-(di-ethylamino)-propyl]$-3-ethylcarbodi-imide (EDC), and Woodward's Reagent K(WRK)inactivated the enzyme, resulting in the residual activity of less than 20%. WRK reduced the enzyme activity by modifying carboxylic amino acids, and the inactivation reacion proceeded in the form of pseudo-first-order kinetics. The double-lagarithmic plot of the observed pseudo-first- order rate constant against the modifier concentration yielded a reaction order of 2, indicating that two carboxylic amino acids were essential for the enzyme activity. The $\beta$-D-xylosidase was also inactivated by N-ethylmaleimide which specifically modified a cysteine residue with a reaction order of 1, implying that one cysteine residue was important for the enzyme activity. Xylobiose protected the enzyme against inactivation by WRK and N-ethylmaleimide, revealing that carboxylic amino acids and a cysteine residue were present at the substrate-binding site of the enzyme molecule.

• Journal of Microbiology and Biotechnology
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• 제9권6호
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• pp.839-846
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• 1999

An extracellular chitinase-producing bacterial strain induced by colloidal chitin was isolated from sea sand and was identified to be a member of the genus Cytophaga. The chitinase was purified successively by 30-60% ammonium sulfate fractionation, and DEAE-Bio gel A column, Octyl-Sepharose CL-4B column, and DEAE-Bio gel A column chromatographies. The enzyme had a molecular mass of 59.75 kDa, and the amino terminal amino acid sequence was ATPNAPVISW MPTDXXLQNXS. The enzyme acted better on colloidal chitin as a substrate than on chitosan. For colloidal chitin and chitosan (Degree of Acetylation, 15-25%), $K_{cat}$ values were 0.60U/mg and 0.08U/mg, respectively. HPLC analysis of the enzymatic reaction products showed that the chitinase produced mostly N-acetyl-D-glucosarnine and di-N-acetylchitobiose. The optimum temperature and pH for the enzyme were $50^{\circ}C$ and 4.0, respectively. N-Bromosuccinimide and $Hg^{2+}$ inhibited the chitinase activity as much as 90%, and $Sb^{3+}$, diethylpyrocarbonate, and $Ag^{+}$ inhibited it by 50-70%.

• Bulletin of the Korean Chemical Society
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• 제22권1호
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• pp.68-76
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• 2001

We have employed chemical modification to identify amino acids essential for the catalytic activity of alliinase (EC 4.4.1.4) from garlic (Allium sativum). Alliinase degrades S-alkyl-L cysteine sulfoxides, causing the characteristic odor of garlic. The activity of alliinase was rapidly and completely inactivated by N-bromosuccinimide(NBS) and slightly decreased by succinic anhydride and N-acetylimidazole. These results indicate that tryptophanyl, lysyl, and tyrosyl residues play an important role in enzyme catalysis. The reaction of alliinase with NBA yielded a characteristic decrease in both the absorbance at 280 nm and the intrinsic fluorescence at 332 nm with increasing reagent concentration of NBS, consistent with the oxidation of tryptophan residues. Kinetic analysis, fluorometric titration of tryptophans and correlation to residual alliinase activity showed that modification of only one residue present on alliinase led to complete inhibition of alliinase activity. To identify this essential tryptophan residue, we employed chemical modification by NBS in the presence and absence of the protecting substrate analogue, S-ethyl-L-cysteine (SEC) and N-terminal sequence analysis of peptide fragment isolated by reverse phase-HPLC. A fragment containing residues 179-188 was isolated. We conclude that Trp182 is essential for alliinase activity.

• Biotechnology and Bioprocess Engineering:BBE
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• 제7권4호
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• pp.216-220
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• 2002

1,4-Benzoquinone reductase was purified to electrophoretic homogeneity from bovine liver, and the purified enzyme found to have a molecular mass of 29 kDa, as determined by sodium dodecyl sulfate- polyacrylamide gel electrophoresis The enzyme exhibited pH optimum between 8.0 and 8.5. The apparent fm for 1,4-benzoqulnone was 1.643 mM, and the apparent Km for NADH was 1.837 mM. Various divalent cations, such as Hg$\^$2+/, Cu$\^$2+/, and Zn$\^$2+/, exhibited strong inhibitory effects. The enzyme activity was also strongly inhibited by quercetin, dicumarol, and benzoic acid. Incubation of the enzyme with N-bromosuccinimide and pyridoxal 5’-phosphate led to inhibitions of 100% and 99%, respectively. Accordingly, these results suggest that trypto-phan and Iysine residues are Involved at or near the active sites of the enzyme.