CYP450 Assay Systems

Description

The P450-Glo™ CYP450 Assays provide a homogeneous, luminescent method for measuring cytochrome P450 activity. The assays are designed to measure the activities of P450s from recombinant and native sources and for testing the effects of analytes such as drugs and new chemical entities on P450 activities. These luminescent assays exhibit exquisite sensitivity, low background signals and broad dynamic range.

P450-Glo™ Assays employ luminogenic P450 substrates that are derivatives of beetle luciferin, a substrate for luciferase enzymes. The derivatives are not substrates for luciferase but are converted by P450s to luciferin, which in turn reacts with luciferase to produce light that is directly proportional to the activity of the P450.

The P450-Glo™ Assays generate a “glow-type” luminescent signal, produced using derivatized luciferins as P450 substrates and a recombinant stabilized luciferase (Ultra-Glo™ Luciferase) coupled with a proprietary buffer system. The half-life of the luminescent output is greater than two hours, eliminating the need for luminometers with injectors and allowing batch plate processing. The formulation also minimizes the incidence of false positives due to inhibition of luciferase by analytes when screening for cytochrome P450 inhibitors.

Drug-induced changes in expression of CYP450 genes are a key cause of drug-drug interactions. The ability to measure enzymatic activity of the specific human isoforms that are induced is critical for developing safer drugs. Currently, the most important inducible human isoforms are CYP1A2, CYP2B6 and CYP3A4. With the introduction of the new P450-Glo™ CYP2B6 Assay we now have assays to measure the activities of all three of these important inducible isoforms. The luciferin-based substrates are readily taken up by cells and rapidly converted into luciferin inside the cell, which reduces the incubation time required (typically 30–60 minutes). The low background and high signal-to-noise ratios produced mean less starting material is required.

Dimethyl sulfoxide (DMSO), a common solvent used to solubilize chemical compounds, can significantly inhibit the activity of the 3A4 isoform of cytochrome P450, even at low concentrations (<0.1%).The P450-Glo™ CYP3A4 System (Luciferin-PPXE) DMSO-Tolerant Assay is specifically designed to tolerate DMSO in the 3A4 reaction. The assay exhibits little to no change in the signal-to-background ratio in the presence of 0.2% DMSO compared to a no-DMSO control.

View Table 1 for cytochrome P450 enzymes, recommended substrates and assay formats.

Features – Benefits

• Obtain Reliable Results: The broad dynamic range, low background and better sensitivity result in less ambiguous data.
• Avoid Fluorescence Interference: Luminescent output eliminates interference from fluorescent test compounds.
• Save Time: Homogeneous assay with simple “add-and-read” format.
• Avoid False Hits: Special formulation results in low false-hit rate.
• Save Money: Scalable to 384-well format, reducing cost per well.
• Automate This Assay: Validated automated methods available at: www.promega.com/automethods/
• Choose Your Configuration: Learn more about our custom options for this product at: www.promega.com/custom/

Applications

• Measure recombinant CYP450 activities in membrane fractions from heterologous expression systems, such as Sf9 cells and E. coli.
• Measure native CYP450 activities in microsomal fractions from tissues.
• Screen drugs and new chemical entities for their capacity to modulate CYP450 activities in native or recombinant fractions.