• Applied Biological Chemistry
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• v.51 no.3
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• pp.153-158
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• 2008

An actinomycetes F-97 producing tyrosinase inhibitor was isolated from soil samples. Isolation and purification of tyrosinase inhibitor produced by F-97 was performed as follows: IRC-120 ($NH_4^+$ type) column chromatography, silica gel column chromatography, $C_{18}$ column chromatography and Sephadex LH-20 column chromatography were used successively after the centrifuged supernatant was adjusted to pH 4.0. To identify the purity of the inhibitor, octadecylsilyl(ODS) HPLC was carried out with 5% methanol as a mobile phase. Finally, the purification yield of a tyrosinase inhibitor was 5.24%. The inhibitor was very soluble in water, methanol and ethanol but insoluble in acetone, butanol, ethylacetate and chloroform. The ${\lambda}_{max}$ value of this inhibitor in water was 194nm under UV light. The biochemical test of the inhibitor was positive in Molish, Benedict, cone. $H_2SO_4$, and $KMnO_4$ tests but negative in iodine, ninhydrin, Million, Sakaguchi, xanthoproteic and Emerson tests. The tyrosinase inhibitor was stable against heat treatment of $100^{\circ}C$ for 50 minutes and pH $4{\sim}9$. The $IC_{50}$ value of this inhibitor was $19.2{\mu}g/ml$ for mushroom tyrosinase. In $1,000{\mu}g/ml$ inhibitor concentration, inhibition zone was 27 mm for Streptomyces bikiniensis NRRL B-1049. The inhibition of F-97 against mushroom tyrosinase was competitive with tyrosine.

• The Journal of Natural Sciences
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• v.16 no.1
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• pp.1-13
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• 2005

The angiotensin I-converting enzyme (ACE) inhibitor has anti-hypertensive effects and has long been used as prevention or remedy of hypertension. This study were carried out to produce and purify a new ACE inhibitor from recombinant E. coli and further elucidate its structure-function relationship. Recombinant pGEX-4T-3 containing ACE inhibitory peptide gene of Saccharomyces cerevisiae was transformed into E. coli BL21(DE3). Glutathione-S transferase (GST) fusion protein from E. Coli BL21(DE3) harboring the recombination pGEX-4T-3 was obtained and the ACE inhibitory peptide was purified with Sephadex G-25 column chromatography. The purified ACE inhibitory peptide was a novel decapeptide with sequence Tyr-Asp-Gly-Gly-Val-Phe -Arg-Val-Tyr-Thr which shows very low similarity to the other ACE inhibitory peptide sequence. The purified ACE inhibitor competitively inhibited ACE.

• Korean Journal of Food Science and Technology
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• v.29 no.6
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• pp.1304-1308
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• 1997

In the course of studies for anti-plaque agents, novel procyanidin structure isolated from Artocarpus heterophyllus folium was established by thiolysis and spectroscopic analysis. The chemical structure was identified for $(-)-epiafzelecin-(4{\beta}{\rightarrow}8)-afzelecin-(4{\alpha}-8)-catechin$ containing the trimeric flavan-3-ols and molecular weight was 833[M-H] by FAB-MS negative ion method. The inhibitory effect on the glucosyltransferase activity was investigated, novel compound showed complete inhibition at 1.0 mM and inhibited on the glucosyltransferase noncompetitively.

• Microbiology and Biotechnology Letters
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• v.18 no.5
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• pp.471-475
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• 1990

A thermostable adenylate kinase isolated from the sonic extracts of Thermus caldophilus cells revealed higher substrate-specificity to the nucleoside monophosphate than to the nucleoside triphosphate. A $P', P^5$-di(adenosine-5') pentaphosphate was acted as a competitive inhibitor to the various substrates. Various divalent cations were activated the enzyme activity following orders: $Mg^{2+}, Ca^{2+}, Mn^{2+}, Ba^[2+}, $ and $Fe^{2+}$-. The enzyme activity was not affected by the sulfurhydryl reagent, p-chloromeric uribenzoic acid and activated by addition of the sodium chloride or phosphoenol pyruvate to the reaction mixture.

• Journal of Life Science
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• v.15 no.4 s.71
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• pp.633-640
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• 2005

The purified xylanase from Bacillus pumilus TX703 was modified with various chemical modifiers to determine the active sites of the enzyme. Treatment of the enzyme with group-specific reagents such as carbodiimide or N-bromosuccinimide resulted in complete loss of enzyme activity. These results assumed that these reagents reacted with glutamic acid or aspartic acid and tryptophan residues located at or near the active site. In each case, inactivation was performed by pseudo first-order kinetics. Inhibition of enzyme activity by carbodiimide and W-bromosuccinimide showed non-competitive and competitive inhibition type, respectively. Addition of xylan to the enzyme solution containing N-bromosuccinimide prevented the inactivation, indicating the presence of tryptophan at the substrate binding site. Analysis of kinetics for inactivation showed that the loss of enzyme activity was due to modification of two glutamic acid or aspartic acid residues and single tryptophan residue.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.2
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• pp.293-297
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• 2016

Hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA reductase) is the rate-limiting enzyme in biosynthesis of cholesterol in animals. In this study, inhibitory effects of isoflavone glycosides on HMG-CoA reductase were investigated. At sample concentration of $100{\mu}M$, genistein-7-O-triglucoside (G2-genistin) inhibited HMG-CoA reductase activity by approximately 18%, whereas daidzein-7-O-triglucoside had no inhibitory effect. In the kinetic experiments with Syrian hamster HMG-CoA reductase, G2-genistin showed inhibitory efficacy with an invariable $V_{max}$ value, suggesting that G2-genistin works as a competitive inhibitor of HMG-CoA reductase and has potential for hypocholesterolemic action through direct regulation of HMG-CoA reductase.

• Journal of the Korean Society of Food Science and Nutrition
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• v.29 no.4
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• pp.719-725
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• 2000

This study focused on the purification and characterization of ACE inhibitor from Porphyra yezoensis. The dried Porphyra yezoensis was ground and hydrolyzed with 2.5 N HCl, followed by neutralization and centrifugation. Then, the subsequential purification of ACE inhibitor was carried out by Amberlite XAD 8, DEAE-Toyopearl 650C, Sephadex LH-20 column chromatography and reverse phase HPLC with C18 column. The purified ACE inhibitor was peptide which consisted of glycine (24.5%), arginine (56.8%) and proline (18.8%). Also, it showed the competitive inhibition pattern to ACE. The apparent molecular mass of purified peptide was 580 dalton, and an IC50 value of ACE inhibitor was 10.6 $\mu\textrm{g}$.

• Korean Journal of Weed Science
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• v.16 no.2
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• pp.122-131
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• 1996

The inhibition characteristics of chlorsulfuron [CHL, 2-chloro-N-[{ (4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino}carbonyl]benzenesulfonamide] and imazaquin [IMA, 2-{4,5-dihydro-4-methyl-4-(1-methy-lethyl)-5-oxo-1H-imidazol-2-yl}-3-quinolinecarboxylic acid] on acetolactate synthase(ALS) activity of corn plants were investigated. CHL and IMA rapidly inhibited ALS activity of corn plants in vitro. Their $I_{50}$ values for ALS activity were 100nM and $5{\mu}M$, respectively, indicating that CHL had 50 times more inhibitory effect on ALS activity than IMA. The first applied herbicide had a dominant inhibitory effect on ALS activity when the two herbicides were applied sequentially. Branched-chain amino acids, valine(Val), leucine(Leu), and isoleucine(Ile) showed a feedback inhibition on ALS activity ; Val or Leu had a more inhibitory effect on ALS activity than Ile. Branchedchain amino acids and CHL or IMA exhibited an additive effect on inhibiting ALS activity. This suggests that branched-chain amino acids inhibit ALS activity by a different mechanisms) from that of CHL or IMA. Apparent ALS activity, which was measured on the basis of the conversion of pyruvate to acetolactate, was decreased by the addition of 2-ketobutyrate into the ALS reaction mixture in a concentration-dependent manner. In addition, kinetic studies revealed that CHL acts as a noncompetitive inhibitor, while IMA acts as an uncompetitive inhibitor to ALS with respect to pyruvate.

• Microbiology and Biotechnology Letters
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• v.15 no.5
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• pp.312-318
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• 1987

The apparent Michaelis constant Km of extracellular adenine deaminase from Streptomyces sp. J-350P was 5.8$\times$10$^{-5}$M. The activation energy or the enzyme was calculated from Arrhenius plots for adenine and the value was 3.13 Kcal/mole. The purine analogues, 6-chloropurine, 2,6-diaminopurine, 6-bromopurine, 4-aminopyrazolo[3,4-d] pyrimidine, 6-iodopurine, and 8-bromoadenine were substrates for the enzyme. 6-Dimethylaminopurine was a competitive inhibitor of the enzyme. The enzyme was inhibited by 0.1mM of Fe$^{3+}$, Ag+, and Hg$^{2+}$ and 1 mM of $\alpha$, $\alpha$＇-dipyridyl, Penta-chiorophenol, and p-chloromercuribenzoate.

• Journal of the Korean Society of Food Science and Nutrition
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• v.22 no.4
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• pp.418-422
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• 1993

For the purpose of utilizing tannins in the functional foods and crude drugs the xanthine oxidase inhibition of tannins isolated from Korean green tea was determined. Acetone extract from Korean green tea showed inhibitory effect against the xanthine oxidase. The galloyl tannins showed higher inhibitory activity against xanthine oxidase than the nongalloyl tannins. In terms of stereo isomers, (-)-epicatechins had higher inhibitory activity than the (+)-catechins. The synergistic activity was also observed. Tannins isolated from Korean green tea appeared to be incompetitive inhibitor against the xanthine oxidase.