Assessment of electrocatalytic hydroxylase activity of cytochrome P450 3A4 (CYP3A4) by means of derivatization of 6β-hydroxycortisol by sulfuric acid for fluorimetric assay

Engineering Electron Transfer Pathway of Cytochrome P450s

Cytochrome P450s (P450s), a superfamily of heme-containing enzymes, existed in animals, plants, and microorganisms. P450s can catalyze various regional and stereoselective oxidation reactions, which are widely used in natural product biosynthesis, drug metabolism, and biotechnology. In a typical catalytic cycle, P450s use redox proteins or domains to mediate electron transfer from NAD(P)H to heme iron. Therefore, the main factors determining the catalytic efficiency of P450s include not only the P450s themselves but also their redox-partners and electron transfer pathways. In this review, the electron transfer pathway engineering strategies of the P450s catalytic system are reviewed from four aspects: cofactor regeneration, selection of redox-partners, P450s and redox-partner engineering, and electrochemically or photochemically driven electron transfer.

Biotransformation of phenytoin in the electrochemically-driven CYP2C19 system

The possibility of the detection of atypical kinetic profiles of drug biotransformation using electrochemical systems based on immobilized cytochromes P450 with phenytoin hydroxylation by cytochrome P450 2C19 (CYP2C19) as an example was evaluated for the first time. For this purpose, we developed an electrochemical system, where one of the electrodes was modified by didodecyldimethylammonium bromide (DDAB) and was used as an electron donor for reduction of heme iron ion of the immobilized CYP2C19 and initiation of the catalytic reaction, while the second electrode was not modified and served for an electrochemical quantitation of 4-hydroxyphenytoin, which is a metabolite of antiepileptic drug phenytoin, by its oxidation peak. It was revealed that the dependence of the rate of 4-hydroxyphenytoin formation on phenytoin concentration is described by the equation for two enzymes or two binding sites indicating the existing of high- and low-affinity forms of the enzyme. The atypical kinetics and the kinetic parameters of CYP2C19-mediated phenytoin hydroxylation in the electrochemical system correlate to the same characteristics obtained by other authors in an alternative enzymatic system. Our results demonstrate the possibility of electrochemical systems based on cytochromes P450 to be applied for the detection of atypical kinetic profiles of drug metabolism.

Predicting drug-drug interactions by electrochemically driven cytochrome P450 3A4 reactions

OBJECTIVES

Human cytochrome P450 3A4 is the most abundant hepatic and intestinal Phase I enzyme that metabolizes approximately 60% marketed drugs. Simultaneous administration of several drugs may result in appearance of drug-drug interaction. Due to the great interest in the combination therapy, the exploration of the role of drug as "perpetrator" or "victim" is important task in pharmacology. In this work the model systems based on electrochemically driven cytochrome P450 3A4 for the analysis of drug combinations was used. We have shown that the analysis of electrochemical parameters of cytochrome P450 3A4 and especially, potential of the start of catalysis, Eonset, possess predictive properties in the determination of the leading ("perpetrator") properties of drug. Based on these experimental data, we concluded, that the more positive potential of the start of catalysis, Eonset, the more pronounced the role of drug as leading medication.

METHODS

Electrochemically driven cytochrome P450 3A4 was used as probe and measuring tool for the estimation of the role of interacting drugs.

RESULTS

It is shown that the electrochemical non-invasive model systems for monitoring the catalytic activity of cytochrome P450 3A4 can be used as prognostic devise in assessment of drug/drug interacting medications.

CONCLUSIONS

Cytochrome P450 3A4 activity was studied in electrochemically driven system. Method was implemented to monitor drug/drug interactions. Based on the obtained experimental data, we can conclude that electrochemical parameter such as potential of onset of catalysis, Eonset, has predictive efficiency in assessment of drug/drug interacting medications in the case of the co-administration.

[Modeling of drug-drug interactions between omeprazole and erythromycin with cytochrome P450 3A4 in vitro assay]

In the present study the electrochemical system based on recombinant cytochrome P450 3A4 (CYP3A4) was used for the investigation of potential drug-drug interaction between medicinal preparations employed for Helicobacter pylori eradication therapy. Drug interactions were demonstrated in association of omeprazole as a proton pump inhibitor (PPI) and macrolide antibiotic erythromycin during cytochrome P450 3A4-mediated metabolism. It was shown that in the presence of omeprazole the rate of N-demethylase activity of CYP3A4 to erythromycin measured by means of product (formaldehyde) formation decreased. Mass-spectrometry analysis of omeprazole sulfone as a CYP3A4-mediated metabolite demonstrated the absence of erythromycin influence on CYP3A4-dependent omeprazole metabolism. This phenomenon may be explained by lower spectral dissociation constant of CYP3A4-omeprazole complex (Kd = 18±2 μM) than that of CYP3A4-erythromycin complex (Kd = 52 μM). Using the electrochemical model of electrochemically-driven drug metabolism it is possible to register CYP3A4-mediated catalytic conversion of certain drugs. In vitro experiments of potential CYP3A4-mediated drug-drug interactions are in accordance with in silico modeling with program PASS and PoSMNA descriptors in the case of omeprazole/erythromycin combinations.