An Intuitive Look at the Relationship of Ki and IC50: A More General Use for the Dixon Plot

Burlingham, Benjamin T.; Widlanski, Theodore S.

doi:10.1021/ed080p214

Cited by 224 publications

(164 citation statements)

References 7 publications

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“…Initial velocities were determined at each of the substrate concentrations tested. Inhibition data for a range of concentrations of each competitive inhibitor at a constant concentration of the nucleotide phosphate donor were plotted as a Dixon plot ([I] vs 1/V) to give the IC 50 value at that [S] as the opposite value of the x intercept (29). K m values were calculated either in the absence or in the presence of increasing concentrations of inhibitor from Lineweaver-Burk double-reciprocal plots of the data.…”

Section: Methodsmentioning

confidence: 99%

Inhibition of Protein Kinase CK2 by Condensed Polyphenolic Derivatives. An in Vitro and in Vivo Study

et al. 2004

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ATP site-directed inhibitors that can target individual kinases are powerful tools for use in signal transduction research, all the more so in the case of a pleiotropic, constitutively active protein kinase such as CK2, which is not turned on in response to specific stimuli. By screening a library of more than 200 derivatives of natural polyphenolic compounds, we have identified 16 molecules which inhibit CK2 with IC 50 values of e1 µM. They belong to the classes of anthraquinones (six compounds), xanthenones (two compounds), fluorenones (one compound), and coumarins (seven compounds), and their inhibitory potency correlates with the presence of nitro, amino, or halogen substituents at specific positions. Three of the most potent inhibitors, MNX (1,8-dihydroxy-4-nitroxanthen-9-one), NBC (8-hydroxy-4-methyl-9-nitrobenzo[g]chromen-2-one), and DBC (3,8-dibromo-7-hydroxy-4-methylchromen-2-one), whose IC 50 values range between 0.13 and 0.36 µM, are quite specific toward CK2 within a panel of 33 protein kinases tested. Treatment of Jurkat cells with these compounds promotes inhibition of endogenous CK2 and induction of apoptosis. A correlation is observed between their efficacy as CK2 inhibitors (as judged from IC 50 values) and their capacity to induce cell death (DC 50 values). Mutations of the unique CK2R residues Val66 and/or Ile174 to alanine have a detrimental effect on inhibition by these compounds with 16-67-fold increases in IC 50 values. The combined usage of these reagents can be exploited to gain information about cellular functions mediated by CK2.

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Section: Methodsmentioning

confidence: 99%

Inhibition of Protein Kinase CK2 by Condensed Polyphenolic Derivatives. An in Vitro and in Vivo Study

et al. 2004

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“…This downstream factor indicates signaling that is induced by Gprotein-coupled receptors, in which cAMP levels increase upon activation of the receptors or decrease upon inhibition of the receptors (Tate, 2012). For all of the assays, classic enzyme kinetics are the basis for calculating pharmacological determinants (i.e., IC 50 , EC 50 , and K i values; Burlingham & Widlanski, 2003;Cheng & Prusoff, 1973).…”

Section: Methods For Studying Transporter and Receptor Pharmacology Imentioning

confidence: 99%

“…With these considerations comparison of IC 50 values within one laboratory is unproblematic. For direct comparison of pharmacological constants between different laboratories K i values should be assessed, since IC 50 but not K i values depend significantly on assay conditions (Burlingham & Widlanski, 2003). The determination of K i values is more complex because it requires knowledge or assessment of the mode of inhibition (e.g., competitive, noncompetitive, or mixed; Burlingham & Widlanski, 2003).…”

Section: Methods For Studying Transporter and Receptor Pharmacology Imentioning

confidence: 99%

“…For direct comparison of pharmacological constants between different laboratories K i values should be assessed, since IC 50 but not K i values depend significantly on assay conditions (Burlingham & Widlanski, 2003). The determination of K i values is more complex because it requires knowledge or assessment of the mode of inhibition (e.g., competitive, noncompetitive, or mixed; Burlingham & Widlanski, 2003). Although K i values would be the best constants to determine, the rapid and extensive characterization of the effects of a large set of cathinone NPS on multiple targets usually does not allow the labor-intensive determination of K i values.…”

Section: Methods For Studying Transporter and Receptor Pharmacology Imentioning

confidence: 99%

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Interactions of Cathinone NPS with Human Transporters and Receptors in Transfected Cells

Simmler

Liechti

2016

Current Topics in Behavioral Neurosciences

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Pharmacological assays carried out in transfected cells have been very useful for describing the mechanism of action of cathinone new psychoactive substances (NPS). These in vitro characterizations provide fast and reliable information on psychoactive substances soon after they emerge for recreational use. Well-investigated comparator compounds, such as methamphetamine, 3,4-methylenedioxymethamphetamine, cocaine, and lysergic acid diethylamide, should always be included in the characterization to enhance the translation of the in vitro data into clinically useful information. We classified cathinone NPS according to their pharmacology at monoamine transporters and receptors. Cathinone NPS are monoamine uptake inhibitors and most induce transportermediated monoamine efflux with weak to no activity at pre-or postsynaptic receptors. Cathinones with a nitrogen-containing pyrrolidine ring emerged as NPS that are extremely potent transporter inhibitors but not monoamine releasers. Cathinones exhibit clinically relevant differences in relative potencies at serotonin vs. dopamine transporters. Additionally, cathinone NPS have more dopaminergic vs. serotonergic properties compared with their non-β-keto amphetamine analogs, suggesting more stimulant and reinforcing properties. In conclusion, in vitro pharmacological assays in heterologous expression systems help to predict the psychoactive and toxicological effects of NPS.

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“…3) were analyzed by Dixon 26,39 and Lineweaver-Burk 26 plots to evaluate the possible mechanisms of enzyme inhibition.…”

Section: Determination Of Cyp Activitiesmentioning

confidence: 99%

Interaction of selected platinum(II) complexes containing roscovitine-based CDK inhibitors as ligands with human liver microsomal cytochrome P450

Mašek¹,

Štarha²,

Harvanová³

et al. 2015

Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub

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Background. We studied the interaction of oxaliplatin derivatives involving cytotoxic adenine-based cyclin-dependent kinase inhibitors, with human liver microsomal cytochrome P450. Methods and Results. The activities of 9 human liver microsomal CYP forms (CYPs 1A2, 7-ethoxyresorufin O-deethylation; 2A6, coumarin 7-hydroxylation; 2B6, 7-ethoxy-4-(trifluoromethyl) coumarin O-deethylation; 2C8, luciferin-6´ methyl ether demethylation; 2C9, diclofenac 4´-hydroxylation, 6´-deoxyluciferin hydroxylation; 2C19, (S)-mephenytoin 4´-hydroxylation; 2D6, bufuralol 1´-hydroxylation, 2E1, chlorzoxazone 6-hydroxylation; 3A4, testosterone 6β-hydroxylation, luciferin-6´ benzyl ether debenzylation) were tested using HPLC, fluorescence and luminescence product detection. At 100 μM platinum(II) oxalato complex concentration, CYP inhibition was in general 25%-50%, except for the CYP3A4 form which showed roughly twice the inhibition (72%-95%). At low complex concentration (10 μM), the difference in inhibition of CYP3A4 and other forms was even more pronounced. Dixon and LineweaverBurk plots indicated a partially noncompetitive mechanism of CYP3A4 inhibition. Conclusions. The tested complexes significantly inhibit human liver microsomal CYP3A4 activity even at clinically relevant concentrations. This could be a serious drawback for the use of these compounds in clinical practice.

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An Intuitive Look at the Relationship of Ki and IC50: A More General Use for the Dixon Plot

Cited by 224 publications

References 7 publications

Inhibition of Protein Kinase CK2 by Condensed Polyphenolic Derivatives. An in Vitro and in Vivo Study

Inhibition of Protein Kinase CK2 by Condensed Polyphenolic Derivatives. An in Vitro and in Vivo Study

Interactions of Cathinone NPS with Human Transporters and Receptors in Transfected Cells

Interaction of selected platinum(II) complexes containing roscovitine-based CDK inhibitors as ligands with human liver microsomal cytochrome P450

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