• Journal of Microbiology and Biotechnology
• /
• v.22 no.12
• /
• pp.1758-1766
• /
• 2012

An extensive investigation was carried out to describe the kinetics of cell growth, substrate consumption, and product formation in the batch fermentation using starch as substrate. Evaluation of intrinsic kinetic parameters was carried out using a best-fit unstructured model. A nonlinear regression technique was applied for computational purpose. The Andrew's model showed a comparatively better $R^2$ value among all tested models. The values of specific growth rate (${\mu}_{max}$), saturation constant ($K_S$), inhibition constant ($K_I$), and $Y_{X/S}$ were found to be 0.109 $h^{-1}$, 11.1 g/l, 0.012 g/l, and 1.003, respectively. The Leudeking-Piret model was used to study the product formation kinetics and the process was found to be growth-associated. The growth-associated constant (${\alpha}$) for protease production was sensitive to substrate concentration. Its value was fairly constant up to a substrate concentration of 30.8 g/l, and then decreased.

• International Journal of Industrial Entomology and Biomaterials
• /
• v.1 no.1
• /
• pp.73-78
• /
• 2000

We investigated some biochemical properties of acetylcholinesterase (AChE) in the Bombyx mori larval head. 1% Triton X-100 (v/v) was suitable for extracting AChE from the silkworm larval head but 1 M NaCl was not suitable. PAGE analysis showed a single band of AChE that was detected by histochemical staining using acetylthiocholine as a substrate. AChE was also partially purified with Sepharose 6B and DEAE-cellulose column. Finally, the specific activity of partially purified enzyme solution was 7.6. The study on inhibitor specificity indicated that the enzyme under study was a true cholinesterase (ChE) or AChE. AChE activity was maximum at the substrate concentration of $5{\times}10^{-4}$ M and the excess substrate inhibited the AChE activity. The optimal pH and temperature were pH 7.0-9.0 and 30-35$^{\circ}C$.

• BMB Reports
• /
• v.31 no.1
• /
• pp.25-30
• /
• 1998

Kinetic studies of L-Alanine dehydrogenase from Bacillus subtilis-catalyzed reactions in the presence of $Zn^{2+}$ were carried out. The substrate (L-alanine) saturation curve is hyperbolic in the absence of the metal ion but it becomes sigmoidal when $Zn^{2+}$ is added to the reaction mixture indicating the positive cooperative binding of the substrate in the presence of zinc ion. The cooperativity of substrate binding depends on the xinc ion concentration: the Hill coefficients ($n_H$) varied from 1.0 to 1.95 when the zinc ion concentration varied from 0 to $60\;{\mu}m$. The inhibition of AlaDH by $Zn^{2+}$ is reversible and noncompetitive with respect to $NAD^+$ ($K_i\;=\;5.28{\times}10^{-5}\;M$). $Zn^{2+}$ itself binds to AlaDH with positive cooperativity and the cooperativity is independent of substrate concentration. The Hill coefficients of substrate biding in the presence of $Zn^{2+}$ are not affected by the enzyme concentration indicating that $Zn^{2+}$ binding does not change the polymerization-depolymerization equilibria of the enzyme. Among other metal ions, $Zn^{2+}$ appears to be a specific reversible inhibitor inducing conformational change through the intersubunit interaction. These results indicate that $Zn^{2+}$ is an allosteric competitive inhibitor and substrate being a non-cooperative per se, excludes the $Zn^{2+}$ from its binding site and thus exhibits positive cooperativity. The allosteric mechanism of AlaDh from Bacillus subtilis is consistent with both MWC and Koshland's allosteric model.

• Archives of Pharmacal Research
• /
• v.21 no.6
• /
• pp.782-784
• /
• 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.

• Journal of Korean Society of Water and Wastewater
• /
• v.12 no.1
• /
• pp.96-101
• /
• 1998

Substrate inhibition of 2,4-dinitrophenol (DNP) degradation was investigated using activated sludge which had been adapted to mineralize DNP. DNP is a metabolic uncoupler, preventing cells from making energy for growth and it has been suggested that pH may be important in mitigating effects of uncouplers. After acclimation of the activated sludge, the effect of pH on toxicity of DNP at high concentration (75 mg/L) was investigated, over a pH range of 5 to 9. DNP inhibition was found to be strongly dependent on mixed liquor pH. The DNP degradation rate was highest in the pH range of 6.95 to 7.84; at pH 5.94 degradation of 75 mg/L DNP was significantly inhibited; at pH < 5.77, DNP degradation was completely inhibited after approximately 30% of the DNP was degraded. By comparison, no significant effect of pH variation in the same range was seen on glucose uptake by the activated sludge culture.

• KSBB Journal
• /
• v.14 no.2
• /
• pp.136-140
• /
• 1999

Characteristics of organic acid degradation by isolated yeast strain was investigated. Optimum initial pH was 5. Increase in cell mass was proportional to the decrease in organic acid degradation. Also no accumulation of byproduct was observed during degradation. Acetic acid degraded fast, followed by butyric acid and propionic acid in order. No significant substrate inhibition was observed up to 12 g/L of acetic acid 7 g/L of propionic acid, respectively. However, inhibition of butyric acid was significant above 4 g/L. Cell mass yield was 0.2-0.4 g cell/g acids and decreased at high decreased at high organic acid concentration. 95% of organic acid (7.5 g/L), corresponding to 13,000 ppm, was degraded in 30-40 hours.

• Biomedical Science Letters
• /
• v.14 no.1
• /
• pp.63-68
• /
• 2008

The aqueous extract from the fruit body of Lentinus edodes was evaluated for inhibitory activities against $\alpha$-glucosidase isolated from Spargue-Dawley male rats. A aqueous extract of Lentinus edodes exhibited 13.8% inhibitory activity on using 2 mM p-nitrophenyl $\alpha$-D-glucopyranoside as a substrate ($IC_{50}$ 75.3 mg/ml). The aqueous extract of Lentinus edodes inhibition type on $\alpha$-glucosidase was determined to be competitive inhibition. When it was oral administered to increase of blood glucose levels after STZ-induced in a dose dependent dietary. These results suggest that aqueous extract of Lentinus edodes effect a metabolism of intestine, and thereby reducing the increase of blood glucose after STZ-induced.

• Natural Product Sciences
• /
• v.6 no.2
• /
• pp.70-72
• /
• 2000

The effects of coptisine on monoamine oxidase (EC 1.4.3.4; MAO) activity in mouse brain were investigated. Coptisine showed an inhibitory effect on MAO activity with a concentration-dependent manner. Coptisine exhibited 51.0% inhibition of MAO activity at $9\;{\mu}M$. The $IC_{50}$ value of coptisine was $8.7\;{\mu}M$. Coptisine inhibited MAO activity competitively with kynuramine as a substrate. The $K_i$ value of coptisine was $4.1\;{\mu}M$. These results indicate that coptisine functions to regulate the catecholamine content at biologically active sites.

• Korean Journal of Microbiology
• /
• v.28 no.1
• /
• pp.65-70
• /
• 1990

The objective of the current study is to elucidate the biological roles of proteinase inhibitor in microorganisms. As the first step, a strain of Streptomyces fradiae was selected as a producer of extracellular proteinase inhibitor. The proteinase inhibitor was purified from culture broth through ultrafiltration, gel-filtration and ion-exchange chromatography. Molecular weight of the proteinase inhibitor was estimated to be 16, 800 by SDS polyacrylamide gel electrophoresis. It was found that the proteinase inhibitor inhibited only alkaline serine proteinases such as subtilisin, $\alpha$-chymotrypsin and Promase E but not trypsin and other proteinases. The mode of inhibition against Pronase E with succinyl-phenylalanine-p-nitroanilide as a substrate was competitive.

• YAKHAK HOEJI
• /
• v.38 no.6
• /
• pp.791-794
• /
• 1994

Sixteen kinds of naturally occurring phenolic compounds including 5 stilbenes, 7 flavonoids and 4 anthraquinones were examined in the inhibitory activity against rat liver AADC(aromatic L-amino acid decarboxylase) in vitro, using 5-hydroxytryptophan as a substrate. Three hydroxystilbenes, resveratrol 1, rhapontigenin 3 and piceatanol 5, which were known to be monoamine oxidase A inhibitors, exhibited a significant inhibition against AADC($IC_{50}$=20, 8 and $5\;{\mu}M$, respectively). By the comparison of the activity of each phenolic compound, it was suggested that the 3',4'-dihydroxyphenyl group of stilbenes or flavones was the best pharmacophore for the AADC inhibitory activity.