In vitro and in vivo anti-tumor effect of Trichobakin fused with urokinase-type plasminogen activator ATF-TBK.

BACKGROUND: Trichobakin (TBK), a member of type I ribosome-inactivating proteins (RIPs), was first successfully cloned from Trichosanthes sp Bac Kan 8-98 in Vietnam. Previous study has shown that TBK acts as a potential protein synthesis inhibitor; however, the inhibition efficiency and specificity of TBK on cancer cells remain to be fully elucidated. METHODS AND RESULTS: In this work, we employed TBK and TBK conjugated with a part of the amino-terminal fragment (ATF) of the urokinase-type plasminogen activator (uPA), which contains the Ω-loop that primarily interacts with urokinase-type plasminogen activator receptor, and can be a powerful carrier in the drug delivery to cancer cells. Four different human tumor cell lines and BALB/c mice bearing Lewis lung carcinoma cells (LLC) were used to evaluate the role of TBK and ATF-TBK in the inhibition of tumor growth. Here we showed that the obtained ligand fused RIP (ATF-TBK) reduced the growth of four human cancer cell lines in vitro in the uPA receptor level-dependent manner, including the breast adenocarcinoma MDA-MB 231 cells and MCF7 cells, the prostate carcinoma LNCaP cells and the hepatocellular carcinoma HepG2 cells. Furthermore, the conjugate showed anti-tumor activity and prolonged the survival time of tumor-bearing mice. The ATF-TBK also did not cause the death of mice with doses up to 48 mg/kg, and they were not significantly distinct on parameters of hematology and serum biochemistry between the control and experiment groups. CONCLUSIONS: In conclusion, ATF-TBK reduced the growth of four different human tumor cell lines and inhibited lung tumor growth in a mouse model with little side effects. Hence, the ATF-TBK may be a target to consider as an anti-cancer agent for clinical trials.

Diversity of Structural, Dynamic, and Environmental Effects Explain a Distinctive Functional Role of Transmembrane Domains in the Insulin Receptor Subfamily.

Human InsR, IGF1R, and IRR receptor tyrosine kinases (RTK) of the insulin receptor subfamily play an important role in signaling pathways for a wide range of physiological processes and are directly associated with many pathologies, including neurodegenerative diseases. The disulfide-linked dimeric structure of these receptors is unique among RTKs. Sharing high sequence and structure homology, the receptors differ dramatically in their localization, expression, and functions. In this work, using high-resolution NMR spectroscopy supported by atomistic computer modeling, conformational variability of the transmembrane domains and their interactions with surrounding lipids were found to differ significantly between representatives of the subfamily. Therefore, we suggest that the heterogeneous and highly dynamic membrane environment should be taken into account in the observed diversity of the structural/dynamic organization and mechanisms of activation of InsR, IGF1R, and IRR receptors. This membrane-mediated control of receptor signaling offers an attractive prospect for the development of new targeted therapies for diseases associated with dysfunction of insulin subfamily receptors.

Unusual Cytochrome c552 from Thioalkalivibrio paradoxus: Solution NMR Structure and Interaction with Thiocyanate Dehydrogenase.

The search of a putative physiological electron acceptor for thiocyanate dehydrogenase (TcDH) newly discovered in the thiocyanate-oxidizing bacteria Thioalkalivibrio paradoxus revealed an unusually large, single-heme cytochrome c (CytC552), which was co-purified with TcDH from the periplasm. Recombinant CytC552, produced in Escherichia coli as a mature protein without a signal peptide, has spectral properties similar to the endogenous protein and serves as an in vitro electron acceptor in the TcDH-catalyzed reaction. The CytC552 structure determined by NMR spectroscopy reveals significant differences compared to those of the typical class I bacterial cytochromes c: a high solvent accessible surface area for the heme group and so-called "intrinsically disordered" nature of the histidine-rich N- and C-terminal regions. Comparison of the signal splitting in the heteronuclear NMR spectra of oxidized, reduced, and TcDH-bound CytC552 reveals the heme axial methionine fluxionality. The TcDH binding site on the CytC552 surface was mapped using NMR chemical shift perturbations. Putative TcDH-CytC552 complexes were reconstructed by the information-driven docking approach and used for the analysis of effective electron transfer pathways. The best pathway includes the electron hopping through His528 and Tyr164 of TcDH, and His83 of CytC552 to the heme group in accordance with pH-dependence of TcDH activity with CytC552.

Radiothermometric Study of the Effect of Amino Acid Mutation on the Characteristics of the Enzymatic System.

The radiothermometry (RTM) study of a cytochrome-containing system (CYP102 A1) has been conducted in order to demonstrate the applicability of RTM for monitoring changes in the functional activity of an enzyme in case of its point mutation. The study has been performed with the example of the wild-type cytochrome (WT) and its mutant type A264K. CYP102 A1 is a nanoscale protein-enzymatic system of about 10 nm in size. RTM uses a radio detector and can record the corresponding brightness temperature (Tbr) of the nanoscale enzyme solution within the 3.4-4.2 GHz frequency range during enzyme functioning. It was found that the enzymatic reaction during the lauric acid hydroxylation at the wild-type CYP102 A1 (WT) concentration of ~10-9 M is accompanied by Tbr fluctuations of ~0.5-1 °C. At the same time, no Tbr fluctuations are observed for the mutated forms of the enzyme CYP102 A1 (A264K), where one amino acid was replaced. We know that the activity of CYP102 A1 (WT) is ~4 orders of magnitude higher than that of CYP102 A1 (A264K). We therefore concluded that the disappearance of the fluctuation of Tbr CYP102 A1 (A264K) is associated with a decrease in the activity of the enzyme. This effect can be used to develop new methods for testing the activity of the enzyme that do not require additional labels and expensive equipment, in comparison with calorimetry and spectral methods. The RTM is beginning to find application in the diagnosis of oncological diseases and for the analysis of biochemical processes.

Synthesis, physico-chemical properties and effect of adenosine thiamine triphosphate on vitamin B1 metabolism in the liver of alloxan diabetic rats.

BACKGROUND: Adenosine thiamine triphosphate (AThTP) is a nucleotide discovered in bacteria and some other living organisms more than a decade ago. No biochemical function for AThTP has been established yet, however, experimental data available indicate its possible involvement in metabolic regulation or cell signaling. Metabolism of AThTP in mammals, as well as the feasibility of its pharmacological application, is essentially unstudied. METHODS: Preparative low-pressure chromatography was employed to purify chemically synthesized AThTP with its further analysis by mass spectrometry, HPLC, UV and fluorescence spectroscopy. Enzyme activity assays along with HPLC were used to examine the effects of AThTP and thiamine on vitamin B1 metabolism in the liver of alloxan-induced diabetic rats. RESULTS: An improved procedure for AThTP synthesis and purification is elaborated. Solution stability, optical spectral properties and the molar absorption coefficient for AThTP were determined. The levels of thiamine compounds were found to be increased in the liver of diabetic rats. Neither AThTP nor thiamine treatment affected hepatic vitamin B1 metabolism. Fasting blood glucose concentration was also unchangeable after AThTP or thiamine administration. GENERAL SIGNIFICANCE: Contrast to the widespread view about thiamine deficiency in diabetes, our results clearly shows an adaptive increase in the level of B1 vitamers in the liver of alloxan diabetic rats with no further rising after AThTP or thiamine treatment at a moderate dose. Neither AThTP nor thiamine is effective in glycaemic control. These findings are to be considered in future studies dealing with thiamine or its analogues application to correct metabolic disturbances in diabetes.

Human Lanosterol 14-Alpha Demethylase (CYP51A1) Is a Putative Target for Natural Flavonoid Luteolin 7,3'-Disulfate.

Widespread pathologies such as atherosclerosis, metabolic syndrome and cancer are associated with dysregulation of sterol biosynthesis and metabolism. Cholesterol modulates the signaling pathways of neoplastic transformation and tumor progression. Lanosterol 14-alpha demethylase (cytochrome P450(51), CYP51A1) catalyzes one of the key steps in cholesterol biosynthesis. The fairly low somatic mutation frequency of CYP51A1, its druggability, as well as the possibility of interfering with cholesterol metabolism in cancer cells collectively suggest the clinical importance of CYP51A1. Here, we show that the natural flavonoid, luteolin 7,3'-disulfate, inhibits CYP51A1 activity. We also screened baicalein and luteolin, known to have antitumor activities and low toxicity, for their ability to interact with CYP51A1. The Kd values were estimated using both a surface plasmon resonance optical biosensor and spectral titration assays. Unexpectedly, in the enzymatic activity assays, only the water-soluble form of luteolin-luteolin 7,3'-disulfate-showed the ability to potently inhibit CYP51A1. Based on molecular docking, luteolin 7,3'-disulfate binding suggests blocking of the substrate access channel. However, an alternative site on the proximal surface where the redox partner binds cannot be excluded. Overall, flavonoids have the potential to inhibit the activity of human CYP51A1 and should be further explored for their cholesterol-lowering and anti-cancer activity.

A new insight into subinteractomes of functional antagonists: Thromboxane (CYP5A1) and prostacyclin (CYP8A1) synthases.

The current article aims to summarize all possible spectrum of protein-protein interactions for thromboxane A synthase (CYP5A1) and prostacyclin synthase (CYP8A1). These enzymes metabolize the same substrate (prostaglandin H2 ) and can participate in cardiovascular, inflammatory, immune processes, and apoptosis modulation, as well as significantly influence the risk of cancers. Binary protein-protein and multiprotein complexes are of great importance in enzyme-regulating and signal-transduction pathways. However, protein partners of CYP5A1 and CYP8A1 are not yet fully identified, although both synthases are considered as prospective drug targets. At least 36 novel protein partners of CYP5A1 and CYP8A1 were revealed from different tissue types using an approach based on affinity isolation and mass spectrometry. Enrichment analysis showed that these proteins have different molecular functions: folding (refolding), unfolded protein and chaperon binding, protein transport (export/import), posttranslational modification, protein domain-specific binding, antioxidant activity, and glutathione homeostasis. A significant part of them, belonging to molecular chaperones, were common partners for CYP5A1 and CYP8A1, while other proteins were unique with the tissue-dependent distribution. New aspects of CYP5A1 and CYP8A1 interactomics and hetero-complex formation with different protein partners, including cytochrome P450s are discussed.

Novel alkylaminoethyl derivatives of androstane 3-oximes as anticancer candidates: synthesis and evaluation of cytotoxic effects.

Steroid anticancer drugs are the focus of numerous scientific research efforts. Due to their high cytotoxic effects against tumor cells, some natural or synthetic steroid compounds seem to be promising for the treatment of different classes of cancer. In the present study, fourteen novel O-alkylated oxyimino androst-4-ene derivatives were synthesized from isomerically pure 3E-oximes, using different alkylaminoethyl chlorides. Their in vitro cytotoxic activity was evaluated against eight human cancer cell lines, as well as against normal fetal lung (MRC-5) and human foreskin (BJ) fibroblasts, to test the efficiency and selectivity of the compounds. Most derivatives displayed strong activity against malignant melanoma (G-361), lung adenocarcinoma (A549) and colon adenocarcinoma (HT-29) cell lines. Angiogenesis was assessed in vitro using migration scratch and tube formation assays on HUVEC cells, where partial inhibition of endothelial cell migration was observed for the 17α-(pyridin-2-yl)methyl 2-(morpholin-4-yl)ethyl derivative. Among the compounds that most impaired the growth of lung cancer A549 cells, the (17E)-(pyridin-2-yl)methylidene derivative bearing a 2-(pyrrolidin-1-yl)ethyl substituent induced significant apoptosis in these cells. In combination with low cytotoxicity toward normal MRC-5 cells, this molecule stands out as a good candidate for further anticancer studies. In addition, in vitro investigations against cytochrome P450 enzymes revealed that certain compounds can bind selectively in the active sites of human steroid hydroxylases CYP7, CYP17A1, CYP19A1 or CYP21A2, which could be important for the development of novel activity modulators of these enzymes and identification of possible side effects.

Modified bile acids and androstanes-Novel promising inhibitors of human cytochrome P450 17A1.

Cytochromes P450 are key enzymes for steroid hormone biosynthesis in human body. They are considered as targets for the screening of novel high efficient drugs. The results of screening of bile acids and androstane derivatives toward human recombinant steroid 17α-hydroxylase/17,20-lyase (CYP17A1) are presented in this paper. A group of steroids, binding with micromolar or submicromolar affinity (in a range from 9 µM - less than 0.1 µM), was identified. Results presented here showed that these steroidal compounds are able to decrease rate of hydroxylation of essential CYP17A1 substrate - progesterone, while some compounds completely inhibited enzyme activity. Structure-activity relationship (SAR) analysis based on in vitro and in silico studies showed that high affinity of the enzyme to bile acids derivatives is correlated with side chain hydrophobicity and presence of hydroxyl or keto group at C3 position. From the other side, bile acid-derived compounds with more polar side chain or substituents at C7 and C12 positions possess higher Kd values. Among androstane-derived steroids couple of Δ5-steroids with hydroxyl group at C3 position, as well as 16,17-secosteroids, were found to be high affinity ligands of this enzyme. The data obtained could be useful for the design of novel highly efficient inhibitors of CYP17A1, since the bile acids-derived compounds are for first time recognized as effective CYP17A1 inhibitors.

In vitro interactions of abiraterone, erythromycin, and CYP3A4: implications for drug-drug interactions.

Potential drug-drug interactions of the antitumor drug abiraterone and the macrolide antibiotic erythromycin were studied at the stage of cytochrome P450 3A4 (CYP3A4) biotransformation. Using differential spectroscopy, we have shown that abiraterone is a type II ligand of CYP3A4. The dependence of CYP3A4 spectral changes on the concentration of abiraterone is sigmoidal, which indicates cooperative interactions of CYP3A4 with abiraterone; these interactions were confirmed by molecular docking. The dissociation constant (Kd ) and Hill coefficient (h) values for the CYP3A4-abiraterone complex were calculated as 3.8 ± 0.1 µM and 2.3 ± 0.2, respectively. An electrochemical enzymatic system based on CYP3A4 immobilized on a screen-printed electrode was used to show that abiraterone acts as a competitive inhibitor toward erythromycin N-demethylase activity of CYP3A4 (apparent Ki  = 8.1 ± 1.2 µM), while erythromycin and its products of enzymatic metabolism do not affect abiraterone N-oxidation by CYP3A4. In conclusion, the inhibition properties of abiraterone toward CYP3A4-dependent N-demethylation of erythromycin and the biologically inert behavior of erythromycin toward abiraterone hydroxylation were demonstrated.

Estimation of the inhibiting impact of abiraterone D4A metabolite on human steroid 21-monooxygenase (CYP21A2).

Abiraterone D4A metabolite, the product of 3ß-hydroxysteroid dehydrogenase activity toward abiraterone, may serve as a potential antitumor agent for the treatment of prostate cancer. The main adverse effect of abiraterone is the disruption of corticosteroid biosynthesis, and the more pharmacologically active abiraterone D4A metabolite may have the same issues. We therefore estimated the inhibiting impact of the abiraterone D4A metabolite on one of the key corticosteroidogenic enzymes - human steroid 21-monooxygenase (CYP21A2). Molecular docking of D4A into the active site of CYP21A2 has been predicted to be similar to abiraterone binding with the enzyme. Abiraterone D4A metabolite, similar to abiraterone, induces type II spectral changes of CYP21A2. The spectral dissociation constant for the abiraterone D4A metabolite-CYP21A2 complex was calculated as 3.4 ±â€¯0.5 µM. Abiraterone D4A metabolite demonstrates competitive/mixed type CYP21A2 inhibition with an inhibitory constant of 1.8 ±â€¯0.8 µM, as obtained by Dixon plot. These results make it possible to predict the adverse effects of the new perspective candidate compound for antitumor therapy.

Backbone and side-chain chemical shift assignments for the ribosome-inactivating protein trichobakin (TBK).

Trichobakin (TBK) is a type-I ribosome-inactivating protein (RIP-I), acting as an extremely potent inhibitor of protein synthesis in the cell-free translation system of rabbit reticulocyte lysate (IC50: 3.5 pM). In this respect, TBK surpasses the well-studied highly homologous RIP-I trichosanthin (IC50: 20-27 pM), therefore creation of recombinant toxins based on it is of great interest. TBK needs to penetrate into cytosol through the cell membrane and specifically bind to α-sarcin/ricin loop of 28S ribosome RNA to perform the function of specific RNA depurination. At the moment, there is no detailed structural-dynamic information in solution about diverse states RIP-I can adopt at different stages on the way to protein synthesis inhibition. In this work, we report a near-complete assignment of 1H, 13C, and 15N TBK (27.3 kDa) resonances and analysis of the secondary structure based on the experimental chemical shifts data. This work will serve as a basis for further investigations of the structure, dynamics and interactions of the TBK with its molecular partners using NMR techniques.

Oligonucleotide Preparation Approach for Assembly of DNA Synthons.

An effective oligonucleotide preparation approach for the thermodynamically balanced, inside-out (TBIO) PCR-based assembly of long synthetic DNA molecules (synthons) is described in the current work. We replaced the necessity to purify individual oligonucleotides with just one purification procedure per approximately 500 base pairs (bp) of duplex DNA. So for an enhanced green fluorescent protein (EGFP) gene of 717 bp, we synthesized 24 oligonucleotides with a length of 50 bases and performed just two solid-phase extraction (SPE) purification procedures. It was found that the capacity of ZipTip microextractors, usually used for sample desalting in proteomics, perfectly corresponds to the gene synthesis scale (40-60 pmol). The robustness of the approach was validated with a 65-mer oligonucleotide design of the same gene. The modification of the oligonucleotide concentration gradient from the original TBIO scheme substantially increased the purity of the PCR product. We proposed a mechanism for the formation of supramolecular structures, which often occur during TBIO assembly. By using the proposed workflow, any laboratory with a standard facility for molecular biology manipulation, a 16-channel oligonucleotide synthesizer, and a conventional thermocycler has the ability to prepare one gene with a length of about 700 bp per day.

Affinity Isolation and Mass Spectrometry Identification of Prostacyclin Synthase (PTGIS) Subinteractome.

Prostacyclin synthase (PTGIS; EC 5.3.99.4) catalyzes isomerization of prostaglandin H2 to prostacyclin, a potent vasodilator and inhibitor of platelet aggregation. At present, limited data exist on functional coupling and possible ways of regulating PTGIS due to insufficient information about protein-protein interactions in which this crucial enzyme is involved. The aim of this study is to isolate protein partners for PTGIS from rat tissue lysates. Using CNBr-activated Sepharose 4B with covalently immobilized PTGIS as an affinity sorbent, we confidently identified 58 unique proteins by mass spectrometry (LC-MS/MS). The participation of these proteins in lysate complex formation was characterized by SEC lysate profiling. Several potential members of the PTGIS subinteractome have been validated by surface plasmon resonance (SPR) analysis. SPR revealed that PTGIS interacted with full-length cytochrome P450 2J2 and glutathione S-transferase (GST). In addition, PTGIS was shown to bind synthetic peptides corresponding to sequences of for GSTA1, GSTM1, aldo-keto reductase (AKR1A1), glutaredoxin 3 (GLRX3) and histidine triad nucleotide binding protein 2 (HINT2). Prostacyclin synthase could potentially be involved in functional interactions with identified novel protein partners participating in iron and heme metabolism, oxidative stress, xenobiotic and drugs metabolism, glutathione and prostaglandin metabolism. The possible biological role of the recognized interaction is discussed in the context of PTGIS functioning.

A large-scale comparative analysis of affinity, thermodynamics and functional characteristics of interactions of twelve cytochrome P450 isoforms and their redox partners.

The aim of the present work was to establish the thermodynamic and functional differences in the protein-protein interactions between the components of the P450-dependent mitochondrial (mit) and microsomal (mic) monooxygenase systems using 12 different isoforms of cytochromes P450 and two redox partners, NADPH-dependent cytochrome P450 reductase (CPR) and adrenodoxin (Adx). Comparative analysis of the affinity, thermodynamics, enzymatic activity and the ability for one-electron reduction has been carried out. The study of protein-protein interactions to determine the equilibrium dissociation constants (Kd) was performed using surface plasmon resonance (SPR) biosensor Biacore 3000. We demonstrated that CPR and Adx interacted with both, micCYPs and mitCYPs, with different affinities (Kd values ranged from 0.01 to 2 µM). All complexes of microsomal (micCYP) and mitochondrial (mitCYP) cytochrome P450 with redox partners can be divided into three groups depending on the prevalent role of either enthalpy or entropy contribution. About 90% of CYP/redox partner complexes were entropy-driven, while the contribution of enthalpy and entropy differed significantly in case of mitCYP/Adx complexes. The CYP11A1/Adx complex was enthalpy-driven, while CYP11B1/Adx and CYP11B2/Adx complexes were entropy-driven. Thermodynamic discrimination of mitCYPs/Adx complexes is likely associated with the different functional impact of CYP11A1 and CYP11B. The exception was the enthalpy-entropy-driven (mixed type) CYP21A2/Adx complex. CPR and Adx were able to transfer the first electron to micCYPs while mitCYPs demonstrated high specificity to Adx. Productive catalysis for mitCYPs observed only in the presence of Adx/AdR pair, while in case of steroidogenic micCYPs (CYP17A1, CYP19A1, and CYP21A2) it was found either in the presence of a CPR or an Adx/AdR pair. From the evolutionary point of view, the type 1 electron transport system (mitCYPs, Adx and NADPH-dependent adrenodoxin reductase (AdR)) increased the specialization of protein-protein interactions (PPI) significantly, which was accompanied by an increase in the specificity of electron transfer. In contrast, the evolution of the type 2 electron transport system (micCYPs and CPR) led to an increase in versatility of PPI as demonstrated for steroidogenic microsomal cytochrome P450s. Our data enhance the current understanding of molecular recognition and summarize qualitative and thermodynamic characteristics of protein-protein interactions in the P450-dependent mitochondrial and microsomal monooxygenase systems.

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

We used rapid one-step derivatization of 6ß-hydroxylated hydrocortisone by sulfuric acid for fluorimetric determination of CYP3A4-dependent hydroxylase reaction in the electrochemical system. We have shown that CYP3A4 substrate - hydrocortisone - and its 6ß-hydroxylated product have different emission wavelengths at an excitation λex = 365 nm after treatment with sulfuric acid:ethanol (3:1) mixture (λem = 525 ±â€¯2 nm and λem = 427 ±â€¯2 nm, respectively). The detection limit for 6ß-hydroxycortisol was estimated to be 0.32 µM (corresponding to 0.095 nmol in 300 µL sample) (S/N = 3). Using the fluorimetric method of 6ß-hydroxycortisol detection following the electrolysis of hydrocortisone with CYP3A4 immobilized on a screen-printed graphite electrode modified by didodecyldimethylammonium bromide we have calculated the steady-state kinetic parameters of CYP3A4 for hydrocortisone: the maximal rate of the reaction (Vmax) as 89 ±â€¯5 pmol of product per min per pmol of electroactive enzyme and the Michaelis constant (KM) as 10 ±â€¯2 µM. In our system, ketoconazole inhibited hydroxylase activity of CYP3A4 towards hydrocortisone with the IC50 value of 70 ±â€¯5 nM. The approach proposed for determination of the CYP3A4 electrocatalytic activity can be used for throughput screening of different modulators of this cytochrome P450 isozyme during drug development.

Interaction of 17α-hydroxylase, 17(20)-lyase (CYP17A1) inhibitors - abiraterone and galeterone - with human sterol 14α-demethylase (CYP51A1).

Abiraterone and galeterone induce type I differential spectral changes in human sterol 14α-demethylase (cytochrome P450 51A1, CYP51A1) with the sigmoidal shape of the binding curve. After approximation of the data by Hill model, the half-saturation concentrations (K0.5) were estimated as 22 ±â€¯1 µM and 16 ±â€¯1 µM and the Hill coefficients as 2.4 ±â€¯0.2 and 1.97 ±â€¯0.23 for abiraterone and galeterone, respectively. We analyzed the catalytic activity of CYP51A1 towards abiraterone and galeterone using an electrochemical system based on recombinant CYP51A1 immobilized on the screen-printed graphite electrode (SPE) modified by didodecyldimethylammonium bromide (DDAB) film. The study revealed the amperometric response of CYP51A1 upon addition of abiraterone, which may indicate the substrate properties of abiraterone towards CYP51A1. Galeterone caused negligible amperometric response of CYP51A1. Mass-spectrometric analysis of the products of CYP51A1-dependent electrocatalytic reaction at a controlled potential towards abiraterone and galeterone revealed products with m/z of 366.3 and 405.2, respectively, indicating monohydroxylation of abiraterone and galeterone. We have observed the sigmoidal character of the dependence of the catalytic current on abiraterone concentration. Analysis of molecular docking data demonstrated the ability of abiraterone and galeterone to bind to the active site of CYP51A1, but abiraterone occupies the position closer to the heme.

Different inhibitory effects of azole-containing drugs and pesticides on CYP2C9 polymorphic forms: An in vitro study.

CYP2C9 plays a major role in drug metabolism. It is highly polymorphic and among the variants, CYP2C9*2 and CYP2C9*3 have been known to encode the protein with moderately to markedly reduced catalytic activity. Azole antifungals are among the most frequently used drugs in human pharmacotherapy and represent a widely used class of pesticides to which humans are inevitably exposed. Due to the similarities in CYP organization throughout species, azoles can interact not only with the target fungal CYP51 substrate-binding site but can also modulate the catalytic activity of human cytochrome P450s, including CYP2C9, causing severe adverse effects. In the present study the potency of azole-containing drugs and pesticides to inhibit recombinant wild-type CYP2C9*1 and the allelic variants CYP2C9*2 and CYP2C9*3 was evaluated. Significant differences were found in their affinity to CYP2C9*1, CYP2C9*2, and CYP2C9*3 as well as in the catalytic activity of CYP2C9 allelic variants. Moreover, addition of cytochrome b5 resulted in a decrease of CYP2C9*3 activity to diclofenac in a concentration-dependent manner. Increasing the knowledge of how azoles influence polymorphic variants of CYP2C9 could help individualize drug treatment, leading to optimization of the selection of drugs and doses for individuals based on genetic information.

Isatin-induced increase in the affinity of human ferrochelatase and adrenodoxin reductase interaction.

Isatin (indol-2,3-dione) is an endogenous non-peptide regulator exhibiting a wide range of biological and pharmacological activities, which are poorly characterized in terms of their molecular mechanisms. Identification of many isatin-binding proteins in the mammalian brain and liver suggests that isatin may influence their functions. We have hypothesized that besides direct action on particular protein targets, isatin can act as a regulator of protein-protein interactions (PPIs). In this surface plasmon resonance-based biosensor study we have found that physiologically relevant concentrations of isatin (25-100 µM) increase affinity of interactions between human recombinant ferrochelatase (FECH) and NADPH-dependent adrenodoxin reductase (ADR). In the presence of increasing concentrations of isatin the Kd values demonstrated a significant (up to 6-fold) decrease. It is especially important that the interaction of isatin with each individual protein (FECH, ADR) was basically negligible and therefore could not contribute to the observed effect. This effect was specific only for the FECH/ADR complex formation and was not observed for other protein complexes studied: FECH/cytochrome b5(CYB5A) and FECH/SMAD4.