Related Experiment Video
Updated: Jun 8, 2026
09:33
Formation of Covalent DNA Adducts by Enzymatically Activated Carcinogens and Drugs In Vitro and Their Determination by 32P-postlabeling
Published on: March 20, 2018
Understanding uncoupling in the multiredox centre P450 3A4-BMR model system.
Danilo Degregorio1, Sheila J Sadeghi, Giovanna Di Nardo
1Department of Human and Animal Biology, University of Turin, Via Accademia Albertina 13, Turin, Italy.
Summary
Uncoupling in cytochrome P450 3A4 is an intrinsic property of the haem domain, not significantly affected by reductase linkage. Optimal coupling efficiency depends on NADPH concentration, pH, and ionic strength.
Area of Science:
- Biochemistry
- Enzyme kinetics
- Cytochrome P450 chemistry
Background:
- Understanding electron transfer uncoupling is crucial for cytochrome P450 (CYP) chemistry.
- Cytochrome P450 3A4 (hCYP3A4) plays a vital role in drug metabolism.
- Investigating the interplay between electron transfer and coupling efficiency is key to enzyme function.
Purpose of the Study:
- To investigate the relationship between electron transfer and coupling efficiency in substrate monoxygenation using a chimeric model.
- To determine the influence of regulatory factors on the coupling efficiency of hCYP3A4 and Bacillus megaterium reductase (BMR).
Main Methods:
- Utilized a chimeric system combining hCYP3A4 and the soluble BMR domain.
- Assessed the impact of FAD, FMN, NADPH concentrations, pH, and ionic strength on formaldehyde production and coupling efficiency.
Main Results:
- FAD and FMN, even at high concentrations, did not affect formaldehyde production or coupling efficiency.
- Optimal coupling efficiency was solely dependent on NADPH concentration.
- pH and ionic strength modulated coupling levels, suggesting an influence on BMR-haem domain interactions.
Conclusions:
- Uncoupling is an intrinsic characteristic of the haem domain in cytochrome P450 enzymes.
- Covalent linkage of the reductase to the haem domain has minimal impact on activity coupled to product formation.
More Related Videos
Related Concept Videos
01:17Drug Metabolism: Phase I Reactions
A phase I reaction is a biochemical process that introduces a functionally reactive polar group to a substance. This transformation predominantly occurs in the liver, facilitated by the cytochrome P450 system of hemoproteins situated in the lipophilic endoplasmic reticulum of cells. The metabolite generated through this process can have varying polarities. If it is sufficiently polar, it can be easily excreted in the urine due to its water compatibility. However, if the metabolite is nonpolar,...
01:43Electron Transport Chain: Complex III and IV
During the electron transport chain, electrons from NADH and FADH2 are first transferred to complexes I and II, respectively. These two complexes then transfer the electrons to ubiquinol, which carries them further to complex III. Complex III passes the electrons across the intermembrane space to Cyt c, which carries them further to complex IV. Complex IV donates electrons to oxygen and reduces it to water. As electrons pass through complexes I, III, and IV, the energy released aids the pumping...
01:23Redox Equilibria: Overview
A reduction-oxidation reaction is commonly called a redox reaction. In a redox reaction, electrons are transferred from one species to another rather than being shared between or among atoms. The reducing agent or reductant is the species that loses electrons and gets oxidized in the process. The species that gains electrons and gets reduced in the process is the oxidizing agent or oxidant. Redox reactions are represented as two separate equations called half-reactions, where one equation...
01:27Redox Reactions
Redox reactions are vital biochemical processes that underpin energy metabolism in cells. These reactions involve the transfer of electrons between molecules, occurring in tandem as oxidation and reduction. Oxidation refers to the loss of electrons, while reduction denotes their gain. This coupling ensures the seamless flow of electrons through metabolic pathways. For example, in bacterial metabolism, glucose undergoes oxidation to carbon dioxide, while oxygen is simultaneously reduced to...
01:24Redox Reactions
Oxidation-reduction or redox reactions involve the transfer of electrons from one molecule or atom to another. When an atom gains an electron, another atom must lose an electron, meaning oxidation and reduction must occur together. Since the redox occurs in pairs, the atom that gets oxidized is also called the reducing agent or reductant, and the atom that is reduced is also called the oxidizing agent or oxidant. A straightforward way to remember the definitions of oxidation and reduction is...
01:17Oxidation of Phenols to Quinones
In the presence of oxidizing agents, phenols are oxidized to quinones. Quinones can be easily reduced back to phenols using mild reducing agents. The electron-donating hydroxyl group enhances the reactivity of the aromatic ring, enabling oxidation of the ring even in the absence of an α hydrogen.
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox property is crucial in...
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox property is crucial in...