Site-Directed Mutagenesis of Cytochrome P450scc. II. Effect of Replacement of the Arg425 and Arg426 Residues on the Structural and Functional Properties of the Cytochrome P450scc

Cytochrome P450-dependent monooxygenases, in spite of their wide distribution, can be simply divided into a few groups differing in the location of the electron transfer chain and their composition. The two main groups of cytochrome P450-dependent monooxygenases are the mitochondrial and microsomal enzymes. While in two-component microsomal cytochrome P450-dependent monooxygenases electrons are supplied to cytochrome P450 by a flavoprotein (NADPH-cytochrome P450 reductase), in three-component mitochondrial monooxygenases the electrons are supplied to cytochrome P450 by a low molecular weight protein (ferredoxin). The interaction of cytochrome P450 with NADPH-cytochrome P450 reductase and ferredoxin is the subject of intensive studies. Using chemical modification, chemical cross-linking, and sitedirected mutagenesis, we identified surface exposed positively charged residues of cytochrome P450scc which might be important for interaction with adrenodoxin. Theoretical analysis of the distribution of surface electrostatic potential in cytochrome P450 indicates that in contrast to microsomal monooxygenases, cytochromes P450 of mitochondrial type, and cholesterol side-chain cleavage cytochrome P450 (P450scc) in part, carry on the proximal surface an evidently positively charged site that is formed by residues Arg425 and Arg426. In the present work, to estimate the functional role of Arg425 and Arg426 of cytochrome P450scc, we used site-directed mutagenesis to replace these residues with glutamine. The results indicate that residues Arg425 and Arg426 are involved in the formation of a heme-binding center and electrostatic interaction of cytochrome P450scc with its physiological electron-transfer partner, adrenodoxin.     

Site-Directed Mutagenesis of Cytochrome b5 for Studies of Its Interaction with Cytochrome P450

We have shown earlier that microsomal cytochrome b ₅ can form a specific complex with mitochondrial cytochrome P450 (cytochrome P450scc). The formation of the complex between these two heme proteins was proved spectrophotometrically, by affinity chromatography on immobilized cytochrome b ₅, and by measuring the cholesterol side-chain cleavage activity of cytochrome P450scc in a reconstituted system in the presence of cytochrome b ₅. To further study the mechanism of interaction of these heme proteins and evaluate the role of negatively charged amino acid residues Glu42, Glu48, and Asp65 of cytochrome b ₅, which are located at the site responsible for interaction with electron transfer partners, we used sitedirected mutagenesis to replace residues Glu42 and Glu48 with lysine and residue Asp65 with alanine. The resulting mutant forms of cytochrome b ₅ were expressed in E. coli, and full-length and truncated forms (shortened from the C-terminal sequence due to cleavage of 40 amino acid residues) of these cytochrome b ₅ mutants were purified. Addition of the truncated forms of cytochrome b ₅ (which do not contain the hydrophobic C-terminal sequence responsible for interaction with the membrane) to the reconstituted system containing cytochrome P450scc caused practically no stimulation of catalytic activity, indicating an important role of the hydrophobic fragment of cytochrome b ₅ in its interaction with cytochrome P450scc. However, full-length cytochrome b ₅ and the full-length Glu48Lys and Asp65Ala mutant forms of cytochrome b ₅ stimulated the cholesterol side-chain cleavage reaction catalyzed by cytochrome P450scc by 100%, suggesting that residues Glu48 and Asp65 of cytochrome b ₅ are not directly involved in its interaction with cytochrome P450scc. The replacement of Glu42 for lysine, however, made the Glu42Lys mutant form of cytochrome b ₅ about 40% less effective in stimulation of the cholesterol side-chain cleavage activity of cytochrome P450scc, indicating that residue Glu42 of cytochrome b ₅ is involved in electrostatic interactions with cytochrome P450scc. Residues Glu42 and Glu48 of cytochrome b ₅ appear to participate in electrostatic interaction with microsomal type cytochrome P450.     

Role of Positively Charged Residues Lys267, Lys270, and Arg411 of Cytochrome P450scc (Cyp11A1) in Interaction with Adrenodoxin

Cytochrome P450scc and adrenodoxin are redox proteins of the electron transfer chain of the inner mitochondrial membrane steroid hydroxylases. In the present work site-directed mutagenesis of the charged residues of cytochrome P450scc and adrenodoxin, which might be involved in interaction, was used to study the nature of electrostatic contacts between the hemeprotein and the ferredoxin. The target residues for mutagenesis were selected based on the theoretical model of cytochrome P450scc-adrenodoxin complex and previously reported chemical modification studies of cytochrome P450scc. In the present work, to clarify the molecular mechanism of hemeprotein interaction with ferredoxin, we constructed cytochrome P450scc Lys267, Lys270, and Arg411 mutants and Glu47 mutant of adrenodoxin and analyzed their possible role in electrostatic interaction and the role of these residues in the functional activity of the proteins. Charge neutralization at positions Lys267 or Lys270 of cytochrome P450scc causes no significant effect on the physicochemical and functional properties of cytochrome P450scc. However, cytochrome P450scc mutant Arg411Gln was found to exhibit decreased binding affinity to adrenodoxin and lower activity in the cholesterol side chain cleavage reaction. Studies of the functional properties of Glu47Gln and Glu47Arg adrenodoxin mutants indicate that a negatively charged residue in the loop covering the Fe2S2 cluster, being important for maintenance of the correct architecture of these structural elements of ferredoxin, is not directly involved in electrostatic interaction with cytochrome P450scc. Moreover, our results indicate the presence of at least two different binding (contact) sites on the proximal surface of cytochrome P450scc with different electrostatic input to interaction with adrenodoxin. In the binary complex, the positively charged sites of the proximal surface of cytochrome P450scc well correspond to the two negatively charged sites of adrenodoxin: the "interaction" domain site and the "core" domain site.     

Role of C-terminal sequence of cytochrome P450scc in folding and functional activity

To elucidate the role of Arg472 and C-terminal sequence of the mature form of cytochrome P450scc, a mitochondrial cytochrome P450, in the present work we have performed sequential removal of the C-terminal amino acid residues of the hemeprotein and evaluated their functional role in folding and catalysis. The removal of 2, 4, 7, or 9 amino acid residues (cytochrome P450scc mutants Delta2, Delta4, Delta7, and Delta9) does not significantly affect the physicochemical properties of the truncated forms of cytochrome P450scc, but results in significant increase in the expression level of the hemeprotein in Escherichia coli (Delta4 cytochrome P450scc mutant). However, removal of 10 C-terminal amino acid residues (Delta10 cytochrome P450scc) of mature form of cytochrome P450scc (replacement of codon for Arg472 for stop-codon) is followed by loss of the ability for correct folding in E. coli. Based on these data, it is concluded that the C-terminal amino acid residues of cytochrome P450scc (DeltaArg472-Ala481) play an important role in correct recombinant protein folding and heme binding by cytochrome P450scc during its expression in E. coli, while folding of mitochondrial cytochrome P450scc during its heterologous expression in bacterial cells is more similar to the folding of prokaryotic soluble cytochrome P450's than to microsomal cytochrome P450's.     

The effect of glycerol on cytochrome P450scc (CYP11A1) spin state,activity, and hydration

We examined the effects of glycerol, a stabilizing agent commonly used in cytochrome P450scc purification and analysis, on the spin state, catalytic activity, and molecular volume of the cytochrome. Glycerol induced a sigmoidal low-spin response. The binding of hydroxycholesterol reaction intermediates, but not cholesterol, increased the concentration of glycerol required for the spin transition to be 50% complete (K(1/2)). Glycerol weakened adrenodoxin binding to P450scc but had no effect on CO or 20alpha,22R-dihydroxycholesterol binding. Cytochrome P450scc activity was inhibited by glycerol with the K(1/2) for inhibition being substrate-dependent. The osmotic stress exerted by glycerol on P450scc resulted in decreases in P450scc molecular volume for both the transition to low spin state and the inhibition of activity. From this we determined that two dissociative water molecules are involved in the inhibition of activity with cholesterol as substrate and five or six dissociative waters are involved in the low-spin transition. The dehydration of P450scc by osmotic stress provides an explanation for the effects of glycerol on P450scc spin transition and activity.     

细胞色素P450还原酶与CYP17的共表达及其功能分析*

17α-羟基黄体酮(17α-OH-PROG)是甾体激素类药物的关键中间体,其生物合成主要由细胞色素单加氧酶(CYP17)催化生成。在此过程中,细胞色素 P450还原酶(cytochrome P450 reductase,CPR)作为细胞色素P450 酶电子传递链的重要组成部分,直接影响CYP17的催化效率。为研究不同来源CPR与17α-羟化酶的适配性,首先以人源17α-羟化酶作为研究对象,构建了表达质粒pPIC3.5k-hCYP17,获得了重组毕赤酵母菌株。其次筛选获得3种不同来源CPR,构建了表达质粒 pPICZX-CPR,获得17α-羟化酶与CPR共表达菌株,并在毕赤酵母中进行转化实验,对转化产物进行薄层色谱(TLC)和高效液相色谱(HPLC)分析。结果显示,重组菌株具有17α-羟化酶活性,能够催化黄体酮生成目标产物17α-OH-PROG 以及副产物16α-羟基黄体酮(16α-OH-PROG)。不同来源的CPR与17α-羟化酶共表达与仅表达17α-羟化酶的产率相比均有所提高,其中hCPR-CYP17共表达菌株表现出最高的转化水平,17α-OH-PROG产率提高42%。上述结果表明:17α-羟化酶基因与CPR共表达能够提高其黄体酮17α-羟基化水平。为甾体黄体酮17α-羟基化的生物催化研究提供思路,对甾体药物的工业生产具有重要意义。     

Comparative study of topogenesis of cytochrome P450scc (CYP11A1) and its hybrids with adrenodoxin expressed in <Emphasis Type="Italic">Escherichia coli</Emphasis> cells

Hybrid proteins consisting of the mature form of cytochrome P450scc (mP) and adrenodoxin (Ad), attached to either the NH2- or COOH-terminus (Ad-mP and mP-Ad, respectively), were expressed in E. coli. Spectral and catalytic properties of P450scc were studied using the membrane fraction of E. coli cells. It has been shown that the Ad amino acid sequence attached to the termini of the P450scc-domain neither affects the insertion of a hybrid protein into the cytoplasmic membrane nor influences its heme binding ability. The results suggest that Ad attached to the NH2-terminus does not markedly affect the folding of the P450scc-domain, but cholesterol hydroxylase/lyase activity of the Ad-mP hybrid was found to be much lower than that of the native P450scc enzyme. The modification of the COOH-terminus does not alter the specific P450scc activity, but results in a dramatic increase in the amount of hybrid protein with incorrectly folded P450scc domain.     

Engineering of proteolytically stable NADPH-cytochrome P450 reductase

NADPH-cytochrome P450 reductase (CPR) is a membrane-bound flavoprotein that interacts with the membrane via its N-terminal hydrophobic sequence (residues 1-56). CPR is the main electron transfer component of hydroxylation reactions catalyzed by microsomal cytochrome P450s. The membrane-bound hydrophobic domain of NADPH-cytochrome P450 reductase is easily removed during limited proteolysis and is the subject of spontaneous digestion of membrane-binding fragment at the site Lys56-Ile57 by intracellular trypsin-like proteases that makes the flavoprotein very unstable during purification or expression in E. coli. The removal of the N-terminal hydrophobic sequence of NADPH-cytochrome P450 reductase results in loss of the ability of the flavoprotein to interact and transfer electrons to cytochrome P450. In the present work, by replacement of the lysine residue (Lys56) with Gln using site directed mutagenesis, we prepared the full-length flavoprotein mutant Lys56Gln stable to spontaneous proteolysis but possessing spectral and catalytic properties of the wild type flavoprotein. Limited proteolysis with trypsin and protease from Staphylococcus aureus of highly purified and membrane-bound Lys56Gln mutant of the flavoprotein as well as wild type NADPH-cytochrome P450 reductase allowed localization of some amino acids of the linker fragment of NADPH-cytochrome P450 reductase relative to the membrane. During prolong incubation or with increased trypsin ratio, the mutant form showed an alternative limited proteolysis pattern, indicating the partial accessibility of another site. Nevertheless, the membrane-bound mutant form is stable to trypsinolysis. Truncated forms of the flavoprotein (residues 46-676 of the mutant or 57-676 of wild type NADPH-cytochrome P450 reductase) are unable to transfer electrons to cytochrome P450c17 or P4503A4, confirming the importance of the N-terminal sequence for catalysis. Based on the results obtained in the present work, we suggest a scheme of structural topology of the N-terminal hydrophobic sequence of NADPH-cytochrome P450 reductase in the membrane.     

Cocktail探针药物法评价傣药"雅解沙把" 对大鼠肝药酶P450亚型 CYP1A2、CYP2C19、CYP2E1、CYP3A4 活性的影响

目的:采用cocktail探针药物法研究傣药"雅解沙把"对肝细胞色素P450亚型CYP1A2、CYP2C19、CYP2E1、CYP3A4的影响。方法:将SD大鼠随机分为空白对照组、苯巴比妥钠组(10.8 mg/kg)、"雅解沙把"低剂量组(0.27 g生药/kg)和"雅解沙把"高剂量组(2.43 g生药/kg),按上述剂量灌胃给药,空白对照组灌胃蒸馏水。连续灌胃7天后处死动物,取肝脏制备肝微粒体,以甲硝唑为内标,建立HPLC方法检测Cocktail探针药物奥美拉唑、氯唑沙宗、咖啡因、氨苯砜的代谢情况。结果:与空白对照组比较,"雅解沙把"低剂量组和高剂量组氯唑沙宗的代谢明显升高,氯唑沙宗的含量显著降低(P0.01),"雅解沙把"高剂量组奥美拉唑和氨苯砜的代谢明显升高,奥美拉唑和氨苯砜的含量明显降低(P0.05)。"雅解沙把"低剂量组和高剂量组虽咖啡因代谢较与空白对照组有上升的趋势,但差异无统计学意义(P0.05)。结论:傣药"雅解沙把"能促进肝药酶CYP3A4、CYP2C19、CYP2E1的活性,加速药物代谢,这可能是其解药物毒的作用机制之一。     

Lipid composition and macromolecular crowding effects on CYP2J2‐mediated drug metabolism in nanodiscs

Lipid composition and macromolecular crowding are key external effectors of protein activity and stability whose role varies between different proteins. Therefore, it is imperative to study their effects on individual protein function. CYP2J2 is a membrane‐bound cytochrome P450 in the heart involved in the metabolism of fatty acids and xenobiotics. In order to facilitate this metabolism, cytochrome P450 reductase (CPR), transfers electrons to CYP2J2 from NADPH. Herein, we use nanodiscs to show that lipid composition of the membrane bilayer affects substrate metabolism of the CYP2J2‐CPR nanodisc (ND) system. Differential effects on both NADPH oxidation and substrate metabolism by CYP2J2‐CPR are dependent on the lipid composition. For instance, sphingomyelin containing nanodiscs produced more secondary substrate metabolites than discs of other lipid compositions, implying a possible conformational change leading to processive metabolism. Furthermore, we demonstrate that macromolecular crowding plays a role in the lipid‐solubilized CYP2J2‐CPR system by increasing the K_m and decreasing the V_max, and effect that is size‐dependent. Crowding also affects the CYP2J2‐CPR‐ND system by decreasing both the K_m and V_max for Dextran‐based macromolecular crowding agents, implying an increase in substrate affinity but a lack of metabolism. Finally, protein denaturation studies show that crowding agents destabilize CYP2J2, while the multidomain protein CPR is stabilized. Overall, these studies are the first report on the role of the surrounding lipid environment and macromolecular crowding in modulating enzymatic function of CYP2J2‐CPR membrane protein system.     

CYP78A1 Preferentially Expressed in Developing Inflorescences of Zea mays Encoded a Cytochrome P450-Dependent Lauric Acid 12-Monooxygenase

Cytochrome P450 (P450 or CYP) monooxygenases play an important role in the oxidation of a number of lipophilic substrates including secondary metabolites in higher plants. Larkin reported that CYP78A1 was preferentially expressed in developing inflorescences of Zea mays (Larkin, Plant Mol. Biol. 25: 343-353, 1994). However, the enzymatic function of CYP78A1 hasn’t been clarified yet. To characterized the enzymatic activity of CYP78A1, in this study, CYP78A1 cDNA and tobacco or yeast NADPH-cytochrome P450 oxidoreductase (P450 reductase) was expressed in the yeast Saccharomyces cerevisiae AH22 cells under the control of alcohol dehydrogenase promoter I and terminator. The reduced CO-difference spectrum of a microsomal fraction prepared from the transformed yeast cells expressing CYP78A1 and yeast P450 reductase showed a peak at 449 nm. Based on the spectrum, the content of a P450 molecule was estimated to be 45 pmol P450 equivalent/mg of protein in the microsomal fraction. The recombinant yeast microsomes containing CYP78A1 and yeast P450 reductase were found to catalyze 12-monooxygenation of lauric acid. Based on these results, CYP78A1 preferentially expressed in developing inflorescences of Zea mays appeared to have participated in the monooxygenation of fatty acids.     

Polymorphisms of the Cytochrome P450 (CYP1A1, CYP2E1) and Microsomal Epoxide Hydrolase (mEPHX) Genes in Cystic Fibrosis and Chronic Respiratory Disease

Frequencies of CYP1A1, CYP2E1, and mEPHX polymorphic variants were analyzed in cystic fibrosis, chronic obstructive lung disease, bronchiectatic disease, chronic nonobstructive bronchitis, and recurring bronchitis. Mutations in CYP1A1 and mEPHX were shown to modify the severity of respiratory disorders in cystic fibrosis, the combination of CYP1A1 genotype Val/Val with the very slow mEPHX phenotype being most unfavorable (odds ratio OR = 12.30). Heterozygosity at both CYP1A1 and CYP2E1 was associated with chronic obstructive lung disease and recurring bronchitis (OR = 4.08 and 11.72, respectively). The very slow phenotype of mEPHX was predisposing to chronic respiratory disorders regardless of the CYP1A1 or CYP2E1 alleles (OR = 4.06). Basing on the above correlations, a combination of the very slow mEPHX phenotype with elevated cytochrome P450 (CYP1A1 and CYP2E1) activities was assumed to expedite severe respiratory disorders.     

棉铃虫P450基因CYP9A12酵母表达产物对拟除虫菊酯的代谢作用

细胞色素P450氧化酶解毒代谢作用增强是棉铃虫Helicoverpa armigera对拟除虫菊酯类杀虫剂产生抗性的主要原因,棉铃虫细胞色素P450氧化酶基因CYP9A12的组成型过量表达与拟除虫菊酯抗性相关。为了进一步明确棉铃虫细胞色素P450氧化酶基因CYP9A12与拟除虫菊酯类杀虫剂抗性的关系,采用酿酒酵母Saccharomyces cerevisiae表达系统异源表达了CYP9A12基因,检测了该基因的酵母表达产物对溴氰菊酯、氟氯氰菊酯、甲氰菊酯和联苯菊酯4种药剂的离体代谢作用。结果表明：含有CYP9A12外源基因的重组酵母细胞裂解液对溴氰菊酯、氟氯氰菊酯和联苯菊酯的代谢率分别为8.58,5.85和3.94 pmol/min·mg protein,而没有检测到对甲氰菊酯的代谢。本研究表明了CYP9A12具有代谢多种拟除虫菊酯的能力,也为CYP9A12参与拟除虫菊酯的解毒代谢提供了直接证据。     

细胞色素P450 2D6缺陷型等位基因的家系分析

利用等位基因特民扩增法(ASA)为基础的基因分型法,对细胞色素P4502D6 (CYP2D6)缺陷型等位基因携带者的9个家庭共38个进行了基因分型,并与用右旋美沙芬为 探针的表型分型法进行对比,发现两种方法的结果是一致的,CYP2D6酶缺陷型等位基因呈常染色体隐性遗传。 Abstract:A genotyping method based on the principle of allele-specific amplification and a phenotyping procedure with dextromethorphan as a probe were employed in familial study of nine families with 38 members for the cytochrome P450 2D6(CYP2D6)deficient alleles——CYP2D6A,CYP2D6B,CYP2D6D and CYP2D6T.The results showed that the CYP2D6 deficient alleles were inherited as an autosomal recessive trait.     

Crystal structure of a ferredoxin reductase for the CYP199A2 system from Rhodopseudomonas palustris

Cytochrome P450‐199A2 from Rhodopseudomonas palustris oxidizes para‐substituted benzoic acids and may play a role in lignin and aromatic acid degradation pathways in the bacterium. CYP199A2 has an associated [2Fe‐2S] ferredoxin, palustrisredoxin (Pux) but not a ferredoxin reductase. A genome search identified the palustrisredoxin reductase (PuR) gene. PuR was produced in Escherichia coli and shown to be a flavin‐dependent protein that supports efficient electron transfer from NADH to Pux, thus reconstituting CYP199A2 monooxygenase activity (k_cat = 37.9 s^–1 with 4‐methoxybenzoic acid). The reduction of Pux by PuR shows K_m = 4.2 μM and k_cat = 262 s^–1 in 50 mM Tris, pH 7.4. K_m is increased to 154 μM in the presence of 200 mM KCl, indicating the importance of ionic interactions in PuR/Pux binding. The crystal structure of PuR has been determined at 2.2 Å resolution and found to be closely related to that of other oxygenase‐coupled NADH‐dependent ferredoxin reductases. Residues on the surface that had been proposed to be involved in ferredoxin reductase‐ferredoxin binding are conserved in PuR. However, Lys328 in PuR lies over the FAD isoalloxazine ring and, together with His11 and Gln41, render the electrostatic potential of the surface more positive and may account for the greater involvement of electrostatic interactions in ferredoxin binding by PuR. Consistent with these observations the K328G mutation weakened Pux binding and virtually eliminated the dependence of PuR/Pux binding on salt concentration, thus confirming that the FAD si side surface in the vicinity of Lys328 is the ferredoxin binding site. Proteins 2009. © 2009 Wiley‐Liss, Inc.     

小鼠 CYP2R1的异源表达及其对癌细胞增殖的差异作用

细胞色素P450 (cytochrome P450, CYP450)是一类血红素氧化酶。细胞色素P450家族2亚家族R成员1（cytochrome P450 family 2 subfamily R member 1, CYP2R1）是一种主要在肝组织中表达的维生素D羟化酶。目前,对于小鼠CYP2R1蛋白质的结构、物化特性和病理机制的理了解仍十分有限。本研究结合基因克隆和生物信息学分析,获得小鼠CYP2R1基因CDS序列及其生物学特征。随后,利用pcDNA3.1-CYP2R1真核表达载体,通过细胞划痕、MTT分析、real-time qPCR方法检测异源表达CYP2R1对肺癌细胞A549、胃癌细胞7901、肝癌细胞HepG2以及正常细胞HEK293T细胞的迁移、增殖和细胞周期基因表达的影响,探明其对癌细胞增殖的作用。结果显示,由C57BL/6小鼠肝组织的CYP2R1基因,序列长度1 506 bp,其中,CD_S 468 bp。其编码的155个氨基酸,与其他11个物种间的同源性均较高,其三级结构与人CYP2R1略有不同。构建的pcDNA3.1-CYP2R1真核表达载体,可在体外培养细胞中提高CYP2R1基因mRNA表达105倍以上,蛋白质水平提高约30倍。值得注意的是,异源表达CYP2R1在癌细胞增殖中的作用具有差异性,其中,CYP2R1通过显著降低细胞周期蛋白基因CyclinD1(P<0.05)和Caspase3(P<0.01),而抑制7901细胞的增殖。该研究结果为进一步探索CYP2R1的生物学作用,特别是在分析其对癌细胞增殖方面提供了基础研究数据,并为进一步明确CYP2R1在癌症相关治疗中的重要意义奠定了理论基础。     

Association of polymorphisms of the CYP1A1 and CYP1A2 cytochrome P450 genes with chronic obstructive pulmonary disease in Bashkortostan

The frequencies of polymorphisms of CYP1A1 (2455A/G, 3801T/C) and CYP1A2 (?2464T/delT, ?163C/A) were determined in healthy residents of Bashkortostan (Russians, Tatars, and Bashkirs) and tested for association with chronic obstructive pulmonary disease (COPD). Interethnic differences in the frequency distribution of the CYP1A1 and CYP1A2 polymorphisms were significant. In Tatars and Russians, the CYP1A1 and CYP1A2 haplotype frequencies were similar (χ² = 0.973, df = 3, P = 1.00 and χ² = 1.546, df = 3, P = 0.92, respectively). In Bashkirs, the CYP1A1 haplotype frequencies significantly differed from those in Russians and Tatars (χ² = 12.328, df = 3, P = 0.008 and χ² = 9.218, df = 3, P = 0.034, respectively) owing to a high frequency of CYP1A1*2B (10.17%). Similarly, Bashkirs differed from Russians and Tatars in the CYP1A2 haplotype frequencies (χ² = 18.779, df = 3, P = 0.0001 and χ² = 14.326, df = 3, P = 0.003, respectively). The frequency of the CYP1A2*1D haplotype in Bashkirs was 11.02% in contrast to 2.36% in Tatars and 1.61% in Russians. Allele *D of the CYP1A2 ?2467delT polymorphism was associated with COPD in Tatars (OR = 1.83, 95%CI 1.24–2.71, χ² = 9.48, P = 0.003). CYP1A2*1D was associated with an increased risk of COPD (8.65% vs. 2.36% in controls, χ² = 9.733, P = 0.0027, P _cor = 0.008, OR = 3.908, 95%CI 1.56–10.19). Haplotype CYP1A2*1A was significantly less frequent in patients with COPD (21.05% vs. 30.74%, χ² = 6.319, P = 0.0127, P _cor = 0.038, OR = 0.6012, 95%CI 0.402–0.898). The CYP1A1 polymorphisms were not associated with COPD in residents of Bashkortostan.     

Heterologous expression of fungal cytochromes P450 (CYP5136A1 and CYP5136A3) from the white-rot basidiomycete Phanerochaete chrysosporium: Functionalization with cytochrome b5 in Escherichia coli

Cytochromes P450 from the white-rot basidiomycete Phanerochaete chrysosporium, CYP5136A1 and CYP5136A3, are capable of catalyzing oxygenation reactions of a wide variety of exogenous compounds, implying their significant roles in the metabolism of xenobiotics by the fungus. It is therefore interesting to explore their biochemistry to better understand fungal biology and to enable the use of fungal enzymes in the biotechnology sector. In the present study, we developed heterologous expression systems for CYP5136A1 and CYP5136A3 using the T7 RNA polymerase/promoter system in Escherichia coli. Expression levels of recombinant P450s were dramatically improved by modifications and optimization of their N-terminal amino acid sequences. A CYP5136A1 reaction system was reconstructed in E. coli whole cells by coexpression of CYP5136A1 and a redox partner, NADPH-dependent P450 reductase (CPR). The catalytic activity of CYP5136A1 was significantly increased when cytochrome b₅ (Cyt-b₅) was further coexpressed with CPR, indicating that Cyt-b₅ supports electron transfer reactions from NAD(P)H to CYP5136A1. Notably, P450 reaction occurred in E. coli cells that harbored CYP5136A1 and Cyt-b₅ but not CPR, implying that the reducing equivalents required for the P450 catalytic cycle were transferred via a CPR-independent pathway. Such an “alternative” electron transfer system in CYP5136A1 reaction was also demonstrated using purified enzymes in vitro. The fungal P450 reaction system may be associated with sophisticated electron transfer pathways.