The system of double inhibitions

Keleti, Tamás; Fajszi, Cs.

doi:10.1016/0025-5564(71)90016-2

Cited by 18 publications

(13 citation statements)

References 10 publications

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“…Both systems assume no independent interactions between C 2 and C 3 . Adapted from Keleti and Fajszi (1972), Segel (1975), andMartinez-Irujo et al (1998).…”

Section: S1mentioning

confidence: 99%

Kinetics of biodegradation of binary and ternary mixtures of PAHs

Dimitriou-Christidis¹,

Autenrieth²

2007

Biotech & Bioengineering

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The kinetics of biodegradation of mixtures of polycyclic aromatic hydrocarbons (PAHs) by Sphingomonas paucimobilis strain EPA505 were investigated. The investigation focused on three- and four-ring PAHs, specifically 2-methylphenanthrene, fluoranthene, and pyrene. Uptake rates in aerobic batch suspended cultivations were measured for the individual PAHs and their binary and ternary mixtures. It was observed that kinetics were influenced by the mixture composition and the kinetic properties of the components. A material balance equation containing the Monod model was numerically fitted to uptake data to determine extant kinetic parameters for the individual PAHs. Similarly, equations containing kinetic interaction models derived from enzyme kinetics were fitted to the uptake data obtained from experiments with binary and ternary mixtures. The investigation considered the following interaction types: no-interaction (Monod), pure competitive interaction, noncompetitive or mixed-type interaction, uncompetitive inhibition, and nonspecific interaction based on pure competition (SKIP). Model fit was evaluated based on probabilistic and statistical criteria and inferences were reached about underlying interaction mechanisms based on model fit. Mixture kinetics were most adequately simulated by the pure competitive interaction model with mutual substrate exclusivity. This model is fully predictive, relying only on parameters determined in the sole-PAH experiments. It was shown that for low percent inhibition values and with limited data, pure competitive interaction kinetics may not be evident, resembling no-interaction kinetics. This study is a reasonable starting point for understanding and modeling biodegradation of complex PAH mixtures in engineered and natural systems.

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“…Both systems assume no independent interactions between C 2 and C 3 . Adapted from Keleti and Fajszi (1972), Segel (1975), andMartinez-Irujo et al (1998).…”

Section: S1mentioning

confidence: 99%

Kinetics of biodegradation of binary and ternary mixtures of PAHs

Dimitriou-Christidis¹,

Autenrieth²

2007

Biotech & Bioengineering

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“…The second approach used for competition tests was based on the general scheme of double enzyme inhibition (Keleti and Fajszi, 1971), applied, in this case, to TEA-verapamil blocking of K ϩ channels (see Appendix: Double Inhibition Scheme). An index of interaction between two inhibitors (␥) was introduced, which would be close to 1 in the case of purely independent inhibition, but tended toward infinity (ϱ) in the case of purely competitive inhibition.…”

Section: Fig 1 Lncap Voltage-activated Kmentioning

confidence: 99%

“…Quantitative analysis of ion channel (Ch) inhibition in the presence of two inhibitors (I 1 and I 2 ) was performed in a similar way to the general approach for enzyme double inhibition systems (Keleti and Fajszi, 1971 …”

Section: Appendixmentioning

confidence: 99%

Verapamil Inhibits Proliferation of LNCaP Human Prostate Cancer Cells Influencing K⁺ Channel Gating

et al. 2001

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“…From the fact that both slopes were straight lines it can be concluded that acriflavine acts as a pure inhibitor of acetylcholinesterase [26]. The decrease in slopes and the concomitant increase in Ki(2) observed a t high acriflavine concentrations indicated that the enzyme became less sensitive towards this type of inhibitor.…”

Section: Inhibition Of Acetylcholinesterase By Proflavine and Acriflamentioning

confidence: 95%

Interaction of Proflavine and Acriflavine with Acetylcholinesterase

Wermuth

Brodbeck

1973

European Journal of Biochemistry

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1.Purified acetylcholinesterase from toluene-treated organs of the electric eel (form B) was inhibited in a noncompetitive manner by the acridine derivatives proflavine and acriflavine. With proflavine secondary plots of slopes and intercepts revealed hyperbolic inhibition patterns. The secondary plots of acriflavine showed a biphasic inhibition pattern with two different slopes (slope, > slope,). A similar biphasic inhibition pattern was observed in the Dixon plot. From the two slopes two apparent Ki-values were obtained. Between 0 and 1 pM acriflavine (low concentrations of acriflavine) the apparent inhibition constant was 0.6 pM, a t acriflavine concentrations greater than 1 pM (high concentrations of acriflavine) the apparent inhibition constant was 2.2 pM. The apparent K , values for acetylthiocholine were 52 pM and 99 respectively. The relative V were 0.37 IU and 0.26 IU respectively. At high concentrations of acriflavine the double-reciprocal plot of substrate concentration versus enzyme activity became hyperbolic and the Hill coefficient for acetylthiocholine was 0.6. However, in presence of 2 mM hexamethonium it increased to 0.9.2. Double inhibitor studies were carried out with acriflavine and atropine, d-( +)tubocurarine, hexamethonium, decamethonium, nicotine or tensilone. At a constant concentration of acriflavine, atropine, d.( +)tubocurarine, hexamethonium and to a lesser extent decamethonium decreased the inhibition by acriflavine. Nicotine and tensilone showed no such effect. Yonetani-Theorell plots with atropine, d-( +)tubocurarine, hexamethonium or decamethonium as constant inhibitors and acritlavine as variable inhibitor revealed a decrease in slopes, a t acriflavine concentrations above 1 p3f. At acriflavine concentrations below 1 pM slopes, did not significantly differ from each other for the pairs of inhibitors investigated. From the Yonetani-Theorell plots a-values for acriflavine (fixed inhibitor) and nicotine and tensilone (variable inhibitors) were determined. For slopes, the values ranged between 10 and 100 depending on substrate concentration, for slope, the values were 1-10 a t 0.1 mM substrate and reached infinity at 5 mM substrate.3. Addition of proflavine and acriflavine to acetylcholinesterase produced a bathochromic and hypochromic shift in the visible absorption spectrum. A maximum difference in the spectra was obtained at 465 nm for proflavine and at 472 nm for acriflavine. Spectral titration of acetylcholinesterase with proflavine revealed normal binding with proflavine concentrations up to 22 pM. At higher concentrations the change in absorbance was significantly greater than expected for a simple stoichiometry of one mole of dye bound per mole of active site. The Hill coefficients were 1.03 and 2.26 respectively. The binding of acriflavine followed a theoretical binding curve up to a concentration of 10 @. At higher concentrations the change in absorbance was again greater. For the acriflavine binding the Hill Coefficients were 1.05 and 1.75 respectively. Addition of a seco...

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The system of double inhibitions

Cited by 18 publications

References 10 publications

Kinetics of biodegradation of binary and ternary mixtures of PAHs

Kinetics of biodegradation of binary and ternary mixtures of PAHs

Verapamil Inhibits Proliferation of LNCaP Human Prostate Cancer Cells Influencing K⁺ Channel Gating

Interaction of Proflavine and Acriflavine with Acetylcholinesterase

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The system of double inhibitions

Cited by 18 publications

References 10 publications

Kinetics of biodegradation of binary and ternary mixtures of PAHs

Kinetics of biodegradation of binary and ternary mixtures of PAHs

Verapamil Inhibits Proliferation of LNCaP Human Prostate Cancer Cells Influencing K+ Channel Gating

Interaction of Proflavine and Acriflavine with Acetylcholinesterase

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Verapamil Inhibits Proliferation of LNCaP Human Prostate Cancer Cells Influencing K⁺ Channel Gating