N-terminal truncated cytochrome P450 2B4: catalytic activities and reduction with alternative electron sources

Expanding the catalytic landscape of metalloenzymes with lytic polysaccharide monooxygenases

Lytic polysaccharide monooxygenases (LPMOs) have an essential role in global carbon cycle, industrial biomass processing and microbial pathogenicity by catalysing the oxidative cleavage of recalcitrant polysaccharides. Despite initially being considered monooxygenases, experimental and theoretical studies show that LPMOs are essentially peroxygenases, using a single copper ion and H2O2 for C-H bond oxygenation. Here, we examine LPMO catalysis, emphasizing key studies that have shaped our comprehension of their function, and address side and competing reactions that have partially obscured our understanding. Then, we compare this novel copper-peroxygenase reaction with reactions catalysed by haem iron enzymes, highlighting the different chemistries at play. We conclude by addressing some open questions surrounding LPMO catalysis, including the importance of peroxygenase and monooxygenase reactions in biological contexts, how LPMOs modulate copper site reactivity and potential protective mechanisms against oxidative damage.

[Methods for determining of cytochrome P450 isozymes functional activity]

The review is dedicated to modern methods and technologies for determining of cytochrome P450 isozymes functional activity, such as absorbance and fluorescent spectroscopy, electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), Raman, Mossbauer, and X-ray spectroscopy, surface plasmon resonance (SPR), atomic force microscopy (AFM). Methods of molecular genetic analysis were reviewed from personalized medicine point of view. The use of chromate-mass-spectrometric methods for cytochrome P450-dependent catalytic reactions' products was discussed. The review covers modern electrochemical systems based on cytochrome P450 isozymes for their catalytic activity analysis, their use in practice and further development perspectives for experimental pharmacology, biotechnology and translational medicine.

Use of bioconjugation with cytochrome P450 enzymes

Bioconjugation, defined as chemical modification of biomolecules, is widely employed in biological and biophysical studies. It can expand functional diversity and enable applications ranging from biocatalysis, biosensing and even therapy. This review summarizes how chemical modifications of cytochrome P450 enzymes (P450s or CYPs) have contributed to improving our understanding of these enzymes. Genetic modifications of P450s have also proven very useful but are not covered in this review. Bioconjugation has served to gain structural information and investigate the mechanism of P450s via photoaffinity labeling, mechanism-based inhibition (MBI) and fluorescence studies. P450 surface acetylation and protein cross-linking have contributed to the investigation of protein complexes formation involving P450 and its redox partner or other P450 enzymes. Finally, covalent immobilization on polymer surfaces or electrodes has benefited the areas of biocatalysis and biosensor design. This article is part of a Special Issue entitled: Cytochrome P450 biodiversity and biotechnology, edited by Erika Plettner, Gianfranco Gilardi, Luet Wong, Vlada Urlacher, Jared Goldstone.

[Electrochemical methods for biomedical investigations]

In the review, authors discussed recently published experimental data concerning highly sensitive electrochemical methods and technologies for biomedical investigations in the postgenomic era. Developments in electrochemical biosensors systems for the analysis of various bio objects are also considered: cytochrome P450s, cardiac markers, bacterial cells, the analysis of proteins based on electro oxidized amino acids as a tool for analysis of conformational events. The electroanalysis of catalytic activity of cytochromes P450 allowed developing system for screening of potential substrates, inhibitors or modulators of catalytic functions of this class of hemoproteins. The highly sensitive quartz crystal microbalance (QCM) immunosensor has been developed for analysis of bio affinity interactions of antibodies with troponin I in plasma. The QCM technique allowed real-time monitoring of the kinetic differences in specific interactions and nonspecific sorption, with out multiple labeling procedures and separation steps. The affinity binding process was characterized by the association (ka) and the dissociation (kd) kinetic constants and the equilibrium association (K) constant, calculated using experimental data. Based on the electroactivity of bacterial cells, the electrochemical system for determination of sensitivity of the microbial cells to antibiotics cefepime, ampicillin, amikacin, and erythromycin was proposed. It was shown that the minimally detectable cell number corresponds to 106 CFU per electrode. The electrochemical method allows estimating the degree of E.coli JM109 cells resistance to antibiotics within 2-5 h. Electrosynthesis of polymeric analogs of antibodies for myoglobin (molecularly imprinted polymer, MIP) on the surface of graphite screen-printed electrodes as sensor elements with o- phenylenediamine as the functional monomer was developed. Molecularly imprinted polymers demonstrate selective complementary binding of a template protein molecule (myoglobin) by the "key-lock" principle.

Directed evolution reveals requisite sequence elements in the functional expression of P450 2F1 in Escherichia coli

Cytochrome P450 2F1 (P450 2F1) is expressed exclusively in the human respiratory tract and is implicated in 3-methylindole (3MI)-induced pneumotoxicity via dehydrogenation of 3MI to a reactive electrophilic intermediate, 3-methyleneindolenine (3-MEI). Studies of P450 2F1 to date have been limited by the failure to express this enzyme in Escherichia coli. By contrast, P450 2F3, a caprine homologue that shares 84% sequence identity with P450 2F1 (86 amino acid differences), has been expressed in E. coli at yields greater than 250 nmol/L culture. We hypothesized that a limited number of sequence differences between P450s 2F1 and 2F3 could limit P450 2F1 expression in E. coli and that problematic P450 2F1 sequence elements could be identified by directed evolution. A library of P450 2F1/2F3 mutants was created by DNA family shuffling and screened for expression in E. coli. Three generations of DNA shuffling revealed a mutant (named JH_2F_F3_1_007) with 96.5% nucleotide sequence identity to P450 2F1 and which expressed 119 ± 40 pmol (n = 3, mean ± SD) hemoprotein in 1 mL microaerobic cultures. Across all three generations, two regions were observed where P450 2F3-derived sequence was consistently substituted for P450 2F1 sequence in expressing mutants, encoding nine amino acid differences between P450s 2F1 and 2F3: nucleotides 191-278 (amino acids 65-92) and 794-924 (amino acids 265-305). Chimeras constructed to specifically test the importance of these two regions confirmed that P450 2F3 sequence is essential in both regions for expression in E. coli but that other non-P450 2F1 sequence elements outside of these regions also improved the expression of mutant JH_2F_F3_1_007. Mutant JH_2F_F3_1_007 catalyzed the dehydrogenation of 3MI to 3-MEI as indicated by the observation of glutathione adducts after incubation in the presence of glutathione. The JH_2F_F3_1_007 protein differs from P450 2F1 at only 20 amino acids and should facilitate further studies of the structure-activity relationships of P450s of the 2F subfamily.

[The influence of vitamin B group on monooxygenase activity of cytochrome P450 3A4: pharmacokinetics and electro analysis of catalytic properties]

It was shown that vitamin B group permit to shorten the longitude of diclofenak therapy and to reduce the daytime dose of this drug. All three schemes of diclofenac treatment - only diclofenac, diclofenac plus 2 tablets of Gitagamp (mixture of vitamin B group), and diclofenac plus 4 tablets of Gitagamp--gave maximum value of diclofenal in blood through 1 hour after treatment. In the case of diclofenak treatment without vitamins Cmax corresponds to 1137.2 +/- 82.4 ng/ml, with 2 tablets of Gitagamp--Cmax 1326.7 +/- 122.5 ng/ml, and with 4 tablets--Cmax 2200.4 +/- 111.3 ng/ml. Positive influence of vitamin B group on the decrease of pain syndrome was shown. Pharmacodynamics and pharmacokinetics data were confirmed in electrochemical experiments with cytochrome P450 3A4. For enzyme immobilization screen printed graphite electrodes modified with gold nanoparticles and synthetic membrane-like compound didodecyldimethylammonium bromide (DDAB/Au) were used. Electrochemical analysis reviled the influence of vitamin B group on metabolism of non steroid anti inflammation drug diclofenac catalyzed by cytochrome P450 3A4. Riboflavin was the most effective inhibitor of diclofenac hydroxylation by cytochrome P450 3A4 as was compared at 300 M concentration of vitamin B group (B1, B2, B6). These data confirmed the opportunity of pharmacokinetic parameters regulation and the level of pharmacodynamic effects by the influence of vitamin B group on the catalytic activity of cytochrome P450 3A4.

Cytochrome P450 biosensors—a review

Cytochrome P450 (CYP) is a large family of enzymes containing heme as the active site. Since their discovery and the elucidation of their structure, they have attracted the interest of scientist for many years, particularly due to their catalytic abilities. Since the late 1970s attempts have concentrated on the construction and development of electrochemical sensors. Although sensors based on mediated electron transfer have also been constructed, the direct electron transfer approach has attracted most of the interest. This has enabled the investigation of the electrochemical properties of the various isoforms of CYP. Furthermore, CYP utilized to construct biosensors for the determination of substrates important in environmental monitoring, pharmaceutical industry and clinical practice.

Electrochemical reduction of cytochrome P450 as an approach to the construction of biosensors and bioreactors

In the present review an attempt was made to present an up-to-date amount of the data on electrochemical reduction of the hemoprotein cytochrome P450. The concept and potentialities of enzyme electrodes--transducers--as the main element for construction of electrochemical biosensors were discussed. Different types of electrodes for bioelectrochemistry were analysed. New nanotechnological approaches to cytochrome P450 immobilisation were reported. It was shown that nanobiotechnology in electrochemistry has potential application in manufacturing biosensors and bioreactors for clinical medicine and pharmacology.

Fluorescent assay for riboflavin binding to cytochrome P450 2B4

The interactions between the hemoprotein cytochrome P450 2B4 (CYP 2B4) and riboflavin - a low molecular weight component of the flavoprotein NADPH-dependent cytochrome P450 reductase - were investigated by fluorescence spectroscopy. Riboflavin fluorescence quenching by cytochrome P450 2B4 was used to probe the ligand-enzyme binding (lambda(ex)=385 nm, lambda(em)=520 nm). Fluorescence titration experiments showed formation of a complex between cytochrome P450 2B4 and riboflavin with an apparent dissociation constant value, K(d)=8.8+/-1 microM. The fluorescence intensity of riboflavin was decreased with increasing the cytochrome P450 2B4 concentration, indicating the transfer of resonance excitation energy from riboflavin (energy donor) to the cytochrome P450 2B4 heme (energy acceptor). The data obtained are suggestive of the existence of riboflavin binding site(s) on the hemeprotein molecule.

Functional modulation of a peroxygenase cytochrome P450: novel insight into the mechanisms of peroxygenase and peroxidase enzymes

Cytochrome P450(BSbeta) is a peroxygenase that catalyzes the alpha- or beta-hydroxylation of myristic acid by utilizing H(2)O(2). The wild-type enzyme not only hydroxylated myristic acid, but oxidized 3,5,3',5'-tetramethylbenzidine (TMB), a peroxidase substrate, in a myristic acid-dependent reaction. Study of inhibition of hydroxylation of myristic acid by TMB indicates these two substrates compete for the same highly reactive intermediate during the course of their respective reactions. When deuterated myristic acid was used as a substrate to decrease hydroxylation activity, the rate of TMB oxidation increased. This increased rate of TMB oxidation was greatly enhanced when the R242K mutant enzyme bound with deuterated myristic acid was used. These results suggest that there are critical structural elements at the distal active site which determine whether this enzyme acts as a peroxygenase or a peroxidase.

Photochemical properties of a riboflavins/cytochrome P450 2B4 complex

The present study demonstrates the possible use of a non-covalent complex of riboflavins with cytochrome P450 2B4 (artificial flavocytochrome P450 2B4) for photo-induced intermolecular electron transfer between the isoalloxazine cycle of flavins and the ferric heme group of cytochrome P450 2B4. Riboflavin was used as a light-induced electron donor for the transfer of electrons to cytochrome P450. The quantitative measurement of the photocurrent, generated by photoreduction of non-covalent flavocytochrome P450 2B4, was carried out. In the presence of typical substrates for cytochrome P450 2B4 the decrease of cathodic photocurrent occurred, generated not only by riboflavin itself but also by a riboflavin/cytochrome P450 complex. It was demonstrated that flavocytochromes might serve as molecular amplifiers of a photocurrent, generated upon flavins' reduction. Introduction of flavin residues into the cytochrome P450 molecule transformed this haemoprotein into a photoreceptor and a photodiode and, in addition, into a photosensitive and photo-activated enzyme.