• Journal of Microbiology and Biotechnology
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• 제19권5호
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• pp.447-454
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• 2009

The transport of spermidine into a cyanobacterium, Synechocystis sp. pec 6803, was characterized by measuring the uptake of $^{14}C$-spermidine. Spermidine transport was shown to be saturable with an apparent affinity constant ($K_m$) value of $67{\mu}M$ and a maximal velocity ($V_{max}$) value of 0.45 nmol/min/mg protein. Spermidine uptake was pH-dependent with the pH optimum being 8.0. The competition experiment showed strong inhibition of spermidine uptake by putrescine and spermine, whereas amino acids were hardly inhibitory. The inhibition kinetics of spermidine transport by putrescine and spermine was found to be noncompetitive with $K_i$ values of 292 and $432{\mu}M$, respectively. The inhibition of spermidine transport by various metabolic inhibitors and ionophores suggests that spermidine uptake is energy-dependent. The diminution of cell growth was observed in cells grown at a high concentration of NaCl. Addition of a low concentration of spermidine at 0.5 mM relieved growth inhibition by salt stress. Upshift of the external osmolality generated by either NaCl or sorbitol caused an increased spermidine transport with about 30-40% increase at 10 mosmol/kg upshift.

• Archives of Pharmacal Research
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• 제21권6호
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• pp.782-784
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• 1998

Ginseng total saponin (GTS) can modulate dopaminergic activity at both presynaptic and postsynaptic dopamine receptors (Kim et al, 1998). The present study investigated t he effect of GTS on the bovine adrenal tyrosine hydroxylase (TH), which catalyze L/tyrosine to DOP. GTS inhibited the bovine adrenal TH by 42.4, 51.5 and 55.3% at concentrations of 40, 80 and 100${\mu}g$/ml, respectively. The IC50 value of GTS was 77.5${\mu}g$/ml. GTS exhibited noncompetitive inhibition with a substrate L-tyrosine. The Ki value was 155${\mu}g$/ml.

• Natural Product Sciences
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• 제6권1호
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• pp.36-39
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• 2000

Acorenone, a diterpene isolated from Acorus gramineus, showed strong resistance inhibitory activity against multi-drug resistant microorganisms such as Staphylococcus aureus SA2, which has resistance to 10 usual antibiotics including chloramphenicol (Cm). At the level of $5\;{\mu}g/ml$ when combined with $50\;{\mu}g/ml$ of Cm. Bacterial resistance to Cm is due to the presence in resistant bacteria of an enzyme, chloramphenicol acetyltransferase (CAT), which catalyses the acetyl-CoA dependent acetylation of the antibiotic at C-3 hydroxyl group. To elucidate the mechanism of resistant inhibitory effect, the acorenone which had the strongest resistant inhibitory activity, was investigated on the CAT assay. As the result, the combination of Cm and acorenone showed the strongest inhibitory activity on CAT as noncompetitive and dose dependent manner.

• 한국미생물·생명공학회지
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• 제10권4호
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• pp.283-288
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• 1982

Streptomyces속 균이 생산하는 trypsin inhibitor의 trypsin에 대한 반응성을 조사해 본 결과 본 저해물질은 crystalline trypsin (20.000 unit, hog pancreas)에 대하여 1/8량에서 약 50%의 저해률을 나타내었으며 trypsin에 대한 저해양상은 mixed noncompetitive-competitive inhibition type이었으며 enzyme-inhibitor complex를 빨리 형성하는데 반응액중 isoleucine이 공존하면 활성이 증가되였으며 Ag$_{＋}$ Hg$_{＋＋}$등의 금속ion은 강하게 본 저해물질의 작용을 억제하였다. 저해률은 사용한 기질의 종류에 따라 차이가 나서 albumin을 사용하였을 때는 casein이나 hemoglobin을 사용하였을 때보다 저해률이 높았다. 그러고 혈액의 응고에 대해서도 저해작용을 나타내었다.

• Journal of Microbiology and Biotechnology
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• 제10권1호
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• pp.81-85
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• 2000

An elastase inhibitor, SMFEI02, was isolated from culture broth of Streptomyces lavendulae SMF11. The inhibitor was purified by ultrafiltration followed by XAD-7 column and Dowex-1 anion-exchange chromatographies, and preparative HPLC. The molecular formula was determined to be $C_{14}H_{16}N_2O_2$ (MW244) by HRFAB-MS analysis. The inhibitor was identified to be a diketopiperazine cyclo(S-Phe-S-Pro) by the optical rotation value and MNR spectral data, and showed inhibitory activities for trypsin, chymotrypsin, cathepsin B, and papain as well as elastase with the Ki values ranging from 1.78mM to $2.86{\;}\mu\textrm{m}$. The inhibition showed a competitive mode for elastase, chymotrypsin, and cathepsin B, whereas it showed a noncompetitive mode for trypsin and papain.

• Journal of Microbiology and Biotechnology
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• 제23권9호
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• pp.1206-1211
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• 2013

The selective inhibition of PTP1B has been widely recognized as a potential drug target for the treatment of type 2 diabetes and obesity. In the course of screening for PTP1B inhibitory fungal metabolites, the organic extracts of several fungal species isolated from marine environments were found to exhibit significant inhibitory effects, and the bioassay-guided investigation of these extracts resulted in the isolation of fructigenine A (1), cyclopenol (2), echinulin (3), flavoglaucin (4), and viridicatol (5). The structures of these compounds were determined mainly by analysis of NMR and MS data. These compounds inhibited PTP1B activity with 50% inhibitory concentration values of 10.7, 30.0, 29.4, 13.4, and 64.0 ${\mu}M$, respectively. Furthermore, the kinetic analysis of PTP1B inhibition by compounds 1 and 5 suggested that compound 1 inhibited PTP1B activity in a noncompetitive manner, whereas compound 5 inhibited PTP1B activity in a competitive manner.

• Journal of Microbiology and Biotechnology
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• 제28권11호
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• pp.1806-1813
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• 2018

A new sesquiterpene lactone dimer [1], together with five known compounds (2-6), was isolated from the flowers of Inula britannica. The structures of these compounds were established by extensive spectroscopic studies and chemical evidence. The inhibitory activities of these isolated compounds (1-6) against human neutrophil elastase (HNE) were also evaluated in vitro; compounds 1 and 6 exhibited significant inhibitory effects against HNE activity, with $IC_{50}$ values of 8.2 and $10.4{\mu}m$, respectively, comparable to that of epigallocatechin gallate (EGCG; $IC_{50}=10.9{\mu}M$). In addition, compounds 3 and 5 exhibited moderate HNE inhibitory effects, with $IC_{50}$ values of 21.9 and $42.5{\mu}M$, respectively. In contrast, compounds 2 and 4 exhibited no such activity ($IC_{50}$ > $100{\mu}M$). The mechanism by which 1 and 3 inhibited HNE was noncompetitive inhibition, with inhibition constant ($K_i$) values of 8.0 and $22.8{\mu}M$, respectively.

• Bulletin of the Korean Chemical Society
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• 제21권12호
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• pp.1217-1221
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• 2000

L-alanine dehydrogenase from Bacillus subtilis exhibits allosteric kinetic properties in the presence of $ZN^{2+}$. $ZN^{2+}$ induces the binding of substrate (L-alanine) to be cooperative at pH 8.0. The effect of pH variation between pH 7.0 and pH 10.0 on the inhibition by $ZN^{2+}$ correlates with the pH effect on the $K_m$ values for L-alanine within these pH range indicating that $ZN^{2+}$ and substrate compete for the same site. No such cooperativity is induced by $ZN^{2+}$ when the reaction is carried out at pH 10. At this higher pH, $ZN^{2+}$ binds with the enzyme with lower affinity and noncompetitive with respect to L-alanine. Inhibition of L-alanine dehydrogenase by $ZN^{2+}$ depends on the ionic strength. Increase in KCI concentration reduced the inhibition, but allosteric property in $ZN^{2+}$ binding is conserved. A model for the regulatory mechanism of L-alanine dehydrogenase as a noncooperative substrate-cooperative cofactor allosteric enzyme, which is compatible in both concerted and the sequential allosteric mechanism, is proposed.

• International Journal of Industrial Entomology and Biomaterials
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• 제9권1호
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• pp.29-33
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• 2004

Low molecular weight silk fibroin (LMSF), which was prepared by hydrolysis of silk fibroin using high-temperature and high-pressure method, was found to inhibit the oxidation of L-3,4,-dihydroxyphenylalanine (L-DOPA) catalyzed by mushroom tyrosinase (EC 1.14.18.1). LMSF contained mostly free amino acids such as L-glycine, L-alanine, and L-serine and oligopeptides, mainly glycine-alanine dimer. As a result of analyzing the inhibition kinetics from Lineweaver-Burk plots, L-glycine and glycine-alanine dimer showed noncompetitive behavior while uncompetitive behavior was observed in L-alanine, and L-serine. When weight percent concentration of ${ID_50}$ was compared, L-glycine was most effective on the inhibition and LMSF was also good enough for the inhibition effect of tyrosinase activity. LMSF showed a mixed-type inhibition and the inhibitory mechanism of LMSF might be caused by free amino acids and oligopeptides. As a result of spectroscopic observation with time, initial rate of increase of DOPAchrome decreased remarkably and the time to reach maximum absorbance increased as an increase of the concentration of L-glycine, meaning that L-glycine made itself mainly responsible for the formation of chelate with ${Cu^2+}$ in tyrosinase. However, in case of L-alanine, L-serine, and especially glycine-alanine dimmer, the production of DOPAchrome after an arrival at maximum absorbance decreased, indicating the production of adducts through the reaction with DOPAquinone.

• 생명과학회지
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• 제25권5호
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• pp.487-495
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• 2015

Pseudomonas pseudoalcaligenes KF707에서 정제한 protocatechuate 3,4-dioxygenase의 특징을 조사하기 위하여 pH안정성, 화학적 저해, 화학적 수식과 pH의존성 반응 상수에 대한 실험을 수행하였다. 이 효소는 pH 4.5~10.7에서 안정하였다. L-ascorbate와 glutathione은 Kis가 각각 0.17 mM과 0.86 mM인 경쟁적 저해제였으며, DL-dithiothreitol은 Kis 1.57 mM 및 Kii 8.08 mM의 비경쟁적 저해패턴을 나타내었다. Potassium cyanide, p-hydroxybenzoate 및 sodium azide는 Kis가 각각 55.7 mM, 0.22 mM 및15.64 mM이었으며, Kii는 각각94.1 mM, 8.08 mM, 및 662.64 mM인 비경쟁적 저해패턴을 나타내었다. $FeCl_{2}$는 Kis가 $29{\mu}M$로 가장 우수한 경쟁적 저해제였으며, $FeCl_{3}$, $MnCl_{2}$, $CoCl_{2}$, $HgCl_{2}$, $AlCl_{3}$도 각각 Kis가 1.21 mM, 0.85 mM, 3.98 mM, 0.17 mM 및 0.21 mM인 경쟁적 저해패턴을 보였다. 한편, 다른 금속이온들은 비경쟁적 저해패턴을 나타내었다. pH의존성 반응상수의 실험결과로부터 pK 6.2와 9.4의 촉매부위와 pK 5.5와 9.0의 결합부위가 존재함을 알 수 있었다. Lysine, cysteine, tyrosine, carboxyl과 histidine은 각각의 고유한 화학적 수식제에 의해 수식되었는데, 이는 이들 잔기들이 결합과 촉매에 관여한다는 것을 나타낸다. 위 결과를 토대로 화학적 메커니즘을 제시한다.