Unusual properties of the cytochrome P450 superfamily

Decoding the Role of CYP450 Enzymes in Metabolism and Disease: A Comprehensive Review

Cytochrome P450 (CYP450) is a group of enzymes that play an essential role in Phase I metabolism, with 57 functional genes classified into 18 families in the human genome, of which the CYP1, CYP2, and CYP3 families are prominent. Beyond drug metabolism, CYP enzymes metabolize endogenous compounds such as lipids, proteins, and hormones to maintain physiological homeostasis. Thus, dysregulation of CYP450 enzymes can lead to different endocrine disorders. Moreover, CYP450 enzymes significantly contribute to fatty acid metabolism, cholesterol synthesis, and bile acid biosynthesis, impacting cellular physiology and disease pathogenesis. Their diverse functions emphasize their therapeutic potential in managing hypercholesterolemia and neurodegenerative diseases. Additionally, CYP450 enzymes are implicated in the onset and development of illnesses such as cancer, influencing chemotherapy outcomes. Assessment of CYP450 enzyme expression and activity aids in evaluating liver health state and differentiating between liver diseases, guiding therapeutic decisions, and optimizing drug efficacy. Understanding the roles of CYP450 enzymes and the clinical effect of their genetic polymorphisms is crucial for developing personalized therapeutic strategies and enhancing drug responses in diverse patient populations.

An Active and Versatile Electron Transport System for Cytochrome P450 Monooxygenases from the Alkane Degrading Organism Acinetobacter sp. OC4

Cytochrome P450 monooxygenases (CYPs) are valuable biocatalysts for the oxyfunctionalization of non-activated carbon-hydrogen bonds. Most CYPs rely on electron transport proteins as redox partners. In this study, the ferredoxin reductase (FdR) and ferredoxin (FD) for a cytochrome P450 monooxygenase from Acinetobacter sp. OC4 are investigated. Upon heterologous production of both proteins independently in Escherichia coli, spectral analysis showed their reduction capability towards reporter electron acceptors, e. g., cytochrome c. The individual proteins' specific activity towards cytochrome c reduction was 25 U mg-1. Furthermore, the possibility to enhance electron transfer by artificial fusion of the units was elucidated. FdR and FD were linked by helical linkers [EAAAK]n, flexible glycine linkers [GGGGS]n or rigid proline linkers [EPPPP]n of n=1-4 sequence repetitions. The system with a glycine linker (n=4) reached an appreciable specific activity of 19 U mg-1 towards cytochrome c. Moreover, their ability to drive different members of the CYP153A subfamily is demonstrated. By creating artificial self-sufficient P450s with FdR, FD, and a panel of four CYP153A representatives, effective hydroxylation of n-hexane in a whole-cell system was achieved. The results indicate this protein combination to constitute a functional and versatile surrogate electron transport system for this subfamily.

Murburn posttranslational modifications of proteins: Cellular redox processes and murzyme-mediated metabolo-proteomics

Murburn concept constitutes the thesis that diffusible reactive species or DRS are obligatorily involved in routine metabolic and physiological activities. Murzymes are defined as biomolecules/proteins that generate/modulate/sustain/utilize DRS. Murburn posttranslational modifications (PTMs) result because murburn/murzyme functionalism is integral to cellular existence. Cells must incorporate the inherently stochastic nature of operations mediated by DRS. Due to the earlier/inertial stigmatic perception that DRS are mere agents of chaos, several such outcomes were either understood as deterministic modulations sponsored by house-keeping enzymes or deemed as unregulated nonenzymatic events resulting out of "oxidative stress". In the current review, I dispel the myths around DRS-functions, and undertake systematic parsing and analyses of murburn modifications of proteins. Although it is impossible to demarcate all PTMs into the classical or murburn modalities, telltale signs of the latter are evident from the relative inaccessibility of the locus, non-specificities and mechanistic details. It is pointed out that while many murburn PTMs may be harmless, some others could have deleterious or beneficial physiological implications. Some details of reversible/irreversible modifications of amino acid residues and cofactors that may be subjected to phosphorylation, halogenation, glycosylation, alkylation/acetylation, hydroxylation/oxidation, etc. are listed, along with citations of select proteins where such modifications have been reported. The contexts of these modifications and their significance in (patho)physiology/aging and therapy are also presented. With more balanced explorations and statistically verified data, a definitive understanding of normal versus pathological contexts of murburn modifications would be obtainable in the future.

Review of Eukaryote Cellular Membrane Lipid Composition, with Special Attention to the Fatty Acids

Biological membranes, primarily composed of lipids, envelop each living cell. The intricate composition and organization of membrane lipids, including the variety of fatty acids they encompass, serve a dynamic role in sustaining cellular structural integrity and functionality. Typically, modifications in lipid composition coincide with consequential alterations in universally significant signaling pathways. Exploring the various fatty acids, which serve as the foundational building blocks of membrane lipids, provides crucial insights into the underlying mechanisms governing a myriad of cellular processes, such as membrane fluidity, protein trafficking, signal transduction, intercellular communication, and the etiology of certain metabolic disorders. Furthermore, comprehending how alterations in the lipid composition, especially concerning the fatty acid profile, either contribute to or prevent the onset of pathological conditions stands as a compelling area of research. Hence, this review aims to meticulously introduce the intricacies of membrane lipids and their constituent fatty acids in a healthy organism, thereby illuminating their remarkable diversity and profound influence on cellular function. Furthermore, this review aspires to highlight some potential therapeutic targets for various pathological conditions that may be ameliorated through dietary fatty acid supplements. The initial section of this review expounds on the eukaryotic biomembranes and their complex lipids. Subsequent sections provide insights into the synthesis, membrane incorporation, and distribution of fatty acids across various fractions of membrane lipids. The last section highlights the functional significance of membrane-associated fatty acids and their innate capacity to shape the various cellular physiological responses.

Dual factors required for cytochrome-P450-mediated hydrocarbon ring contraction in bacterial gibberellin phytohormone biosynthesis

Cytochromes P450 (CYPs) are heme-thiolate monooxygenases that prototypically catalyze the insertion of oxygen into unactivated C-H bonds but are capable of mediating more complex reactions. One of the most remarked-upon alternative reactions occurs during biosynthesis of the gibberellin A (GA) phytohormones, involving hydrocarbon ring contraction with coupled aldehyde extrusion of ent-kaurenoic acid to form the first gibberellin intermediate. While the unusual nature of this reaction has long been noted, its mechanistic basis has remained opaque. Building on identification of the relevant CYP114 from bacterial GA biosynthesis, detailed structure-function studies are reported here, including development of in vitro assays as well as crystallographic analyses both in the absence and presence of substrate. These structures provided insight into enzymatic catalysis of this unusual reaction, as exemplified by identification of a key role for the "missing" acid from an otherwise highly conserved acid-alcohol pair of residues. Notably, the results demonstrate that ring contraction requires dual factors, both the use of a dedicated ferredoxin and absence of the otherwise conserved acidic residue, with exclusion of either limiting turnover to just the initiating and more straightforward hydroxylation. The results provide detailed insight into the enzymatic structure-function relationships underlying this fascinating reaction and support the use of a semipinacol mechanism for the unusual ring contraction reaction.

The Role of Cytochrome P450 AbyV in the Final Stages of Abyssomicin C Biosynthesis

Abyssomicin C and its atropisomer are potent inhibitors of bacterial folate metabolism. They possess complex polycyclic structures, and their biosynthesis has been shown to involve several unusual enzymatic transformations. Using a combination of synthesis and in vitro assays we reveal that AbyV, a cytochrome P450 enzyme from the aby gene cluster, catalyses a key late-stage epoxidation required for the installation of the characteristic ether-bridged core of abyssomicin C. The X-ray crystal structure of AbyV has been determined, which in combination with molecular dynamics simulations provides a structural framework for our functional data. This work demonstrates the power of combining selective carbon-13 labelling with NMR spectroscopy as a sensitive tool to interrogate enzyme-catalysed reactions in vitro with no need for purification.

The Role of Cytochrome P450 AbyV in the Final Stages of Abyssomicin C Biosynthesis

Abyssomicin C and its atropisomer are potent inhibitors of bacterial folate metabolism. They possess complex polycyclic structures, and their biosynthesis has been shown to involve several unusual enzymatic transformations. Using a combination of synthesis and in vitro assays we reveal that AbyV, a cytochrome P450 enzyme from the aby gene cluster, catalyses a key late-stage epoxidation required for the installation of the characteristic ether-bridged core of abyssomicin C. The X-ray crystal structure of AbyV has been determined, which in combination with molecular dynamics simulations provides a structural framework for our functional data. This work demonstrates the power of combining selective carbon-13 labelling with NMR spectroscopy as a sensitive tool to interrogate enzyme-catalysed reactions in vitro with no need for purification.

Hijacking Chemical Reactions of P450 Enzymes for Altered Chemical Reactions and Asymmetric Synthesis

Cytochrome P450s are heme-containing enzymes capable of the oxidative transformation of a wide range of organic substrates. A protein scaffold that coordinates the heme iron, and the catalytic pocket residues, together, determine the reaction selectivity and regio- and stereo-selectivity of the P450 enzymes. Different substrates also affect the properties of P450s by binding to its catalytic pocket. Modulating the redox potential of the heme by substituting iron-coordinating residues changes the chemical reaction, the type of cofactor requirement, and the stereoselectivity of P450s. Around hundreds of P450s are experimentally characterized, therefore, a mechanistic understanding of the factors affecting their catalysis is increasingly vital in the age of synthetic biology and biotechnology. Engineering P450s can enable them to catalyze a variety of chemical reactions viz. oxygenation, peroxygenation, cyclopropanation, epoxidation, nitration, etc., to synthesize high-value chiral organic molecules with exceptionally high stereo- and regioselectivity and catalytic efficiency. This review will focus on recent studies of the mechanistic understandings of the modulation of heme redox potential in the engineered P450 variants, and the effect of small decoy molecules, dual function small molecules, and substrate mimetics on the type of chemical reaction and the catalytic cycle of the P450 enzymes.

Engineering medicinal plant-derived CYPs: a promising strategy for production of high-valued secondary metabolites

Cytochorme P450s (CYPs) play a critical role in the catalysis of secondary metabolite biosynthetic pathways. For their commercial use, various strategies for metabolic pathway engineering using CYP as a potential target have been explored. Plants produce a vast diversity of secondary metabolites which are being used to treat various ailments and diseases. Some of these metabolites are difficult to obtain in large quantities limiting their industrial use. Cytochrome P450 enzymes (CYPs) are important catalysts in the biosynthesis of highly valued secondary metabolites, and are found in all domains of life. With the development of high-throughput sequencing and high-resolution mass spectrometry, new biosynthetic pathways and associated CYPs are being identified. In this review, we present CYPs identified from medicinal plants as a potential game changer in the metabolic engineering of secondary metabolic pathways. We present the achievements made so far in enhancing the production of important bioactivities through pathway engineering, giving some popular examples. At last, current challenges and possible strategies to overcome the limitations associated with CYP engineering to enhance the biosynthesis of target secondary metabolites are also highlighted.

Unravelling the role of transient redox partner complexes in P450 electron transfer mechanics

The molecular evolution of cytochromes P450 and associated redox-driven oxidative catalysis remains a mystery in biology. It is widely believed that sterol 14α-demethylase (CYP51), an essential enzyme of sterol biosynthesis, is the ancestor of the whole P450 superfamily given its conservation across species in different biological kingdoms. Herein we have utilized X-ray crystallography, molecular dynamics simulations, phylogenetics and electron transfer measurements to interrogate the nature of P450-redox partner binding using the naturally occurring fusion protein, CYP51-ferredoxin found in the sterol-producing bacterium Methylococcus capsulatus. Our data advocates that the electron transfer mechanics in the M. capsulatus CYP51-ferredoxin fusion protein involves an ensemble of ferredoxin molecules in various orientations and the interactions are transient. Close proximity of ferredoxin, however, is required to complete the substrate-induced large-scale structural switch in the P450 domain that enables proton-coupled electron transfer and subsequent oxygen scission and catalysis. These results have fundamental implications regarding the early evolution of electron transfer proteins and for the redox reactions in the early steps of sterol biosynthesis. They also shed new light on redox protein mechanics and the subsequent diversification of the P450 electron transfer machinery in nature.

25-hydroxyvitamin D-1α-hydroxylase (CYP27B1) induces ectopic calcification

Vascular calcification is an important pathogenesis related to cardiovascular disease and high mortality rate in chronic kidney disease (CKD) patients. It has been well-known that hyper-phosphatemia induces osteochondrogenic transition of vascular smooth muscle cells (VSMCs) resulting ectopic calcification in aortic media, cardiac valve, and kidney. However, the detailed mechanism of the ectopic calcification has been not clarified yet. Here, we found that the co-localization of CYP27B1 with the calcified lesions of aorta and arteries in kidney of klotho mutant (kl/kl) mice, and then investigated the role of CYP27B1 in the mineralization of the VSMCs. Under high phosphate condition, overexpression of CYP27B1 induced calcification and osteocalcin mRNA expression in the VSMCs. Inversely, siRNA-CYP27B1 inhibited high phosphate-induced calcification of the VSMCs. We also found that the accumulated CYP27B1 protein was glycosylated in the kidney of kl/kl mice. Therefore, overexpression of CYP27B1-N310A and CYP27B1-T439A, which are a mutation for N-linked glycosylation site (N310A) and a mutation for O-linked glycosylation site (T439A) in CYP27B1, decreased calcium deposition and expression of RUNX2 induced by high phosphate medium in VSMCs compared with wild-type CYP27B1. These results suggest that extra-renal expression of glycosylated CYP27B1 would be required for ectopic calcification of VSMCs under hyperphosphatemia.

An Unprecedented Number of Cytochrome P450s Are Involved in Secondary Metabolism in Salinispora Species

Cytochrome P450 monooxygenases (CYPs/P450s) are heme thiolate proteins present in species across the biological kingdoms. By virtue of their broad substrate promiscuity and regio- and stereo-selectivity, these enzymes enhance or attribute diversity to secondary metabolites. Actinomycetes species are well-known producers of secondary metabolites, especially Salinispora species. Despite the importance of P450s, a comprehensive comparative analysis of P450s and their role in secondary metabolism in Salinispora species is not reported. We therefore analyzed P450s in 126 strains from three different species Salinispora arenicola, S. pacifica, and S. tropica. The study revealed the presence of 2643 P450s that can be grouped into 45 families and 103 subfamilies. CYP107 and CYP125 families are conserved, and CYP105 and CYP107 families are bloomed (a P450 family with many members) across Salinispora species. Analysis of P450s that are part of secondary metabolite biosynthetic gene clusters (smBGCs) revealed Salinispora species have an unprecedented number of P450s (1236 P450s-47%) part of smBGCs compared to other bacterial species belonging to the genera Streptomyces (23%) and Mycobacterium (11%), phyla Cyanobacteria (8%) and Firmicutes (18%) and the classes Alphaproteobacteria (2%) and Gammaproteobacteria (18%). A peculiar characteristic of up to six P450s in smBGCs was observed in Salinispora species. Future characterization Salinispora species P450s and their smBGCs have the potential for discovering novel secondary metabolites.

Involvement of CYP347W1 in neurotoxin 3-nitropropionic acid-based chemical defense in mustard leaf beetle Phaedon cochleariae

Chrysomelina beetlesstore 3-nitropropionic acid in form of a pretoxin, isoxazolin-5-one glucoside-conjugated ester, to protect themselves against predators. Here we identified a cytochrome P450 monooxygenase, CYP347W1, to be involved in the production of the 3-nitropropionic acid moiety of the isoxazolin-5-one glucoside ester. Knocking down CYP347W1 led to a significant depletion in the concentration of the isoxazolin-5-one glucoside ester and an increase in the concentration of the isoxazolin-5-one glucoside in the larval hemolymph. Enzyme assays with the heterologously expressed CYP347W1 showed free β-alanine was not the direct substrate. Homology modeling indicated that β-alanine-CoA ester can fit into CYP347W1's active site. Furthermore, we proved that Phaedon cochleariae eggs are not able to de novo synthesize 3-NPA, although both isoxazolin-5-one glucoside and its 3-NPA-conjugated ester are present in the eggs. These results provide direct evidence for the involvement of CYP347W1 in the biosynthesis of a P. cochleariae chemical defense compound.

Orphan cytochrome P450 20a1 CRISPR/Cas9 mutants and neurobehavioral phenotypes in zebrafish

Orphan cytochrome P450 (CYP) enzymes are those for which biological substrates and function(s) are unknown. Cytochrome P450 20A1 (CYP20A1) is the last human orphan P450 enzyme, and orthologs occur as single genes in every vertebrate genome sequenced to date. The occurrence of high levels of CYP20A1 transcripts in human substantia nigra and hippocampus and abundant maternal transcripts in zebrafish eggs strongly suggest roles both in the brain and during early embryonic development. Patients with chromosome 2 microdeletions including CYP20A1 show hyperactivity and bouts of anxiety, among other conditions. Here, we created zebrafish cyp20a1 mutants using CRISPR/Cas9, providing vertebrate models with which to study the role of CYP20A1 in behavior and other neurodevelopmental functions. The homozygous cyp20a1 null mutants exhibited significant behavioral differences from wild-type zebrafish, both in larval and adult animals. Larval cyp20a1-/- mutants exhibited a strong increase in light-simulated movement (i.e., light-dark assay), which was interpreted as hyperactivity. Further, the larvae exhibited mild hypoactivity during the adaptation period of the optomotor assays. Adult cyp20a1 null fish showed a pronounced delay in adapting to new environments, which is consistent with an anxiety paradigm. Taken together with our earlier morpholino cyp20a1 knockdown results, the results described herein suggest that the orphan CYP20A1 has a neurophysiological role.

Advances in production and structural derivatization of the promising molecule ursolic acid

Ursolic acid (UA) is a ursane-type pentacyclic triterpenoid compound, naturally produced in plants via specialized metabolism and exhibits vast range of remarkable physiological activities and pharmacological manifestations. Owing to significant safety and efficacy in different medical conditions, UA may serve as a backbone to produce its derivatives with novel therapeutic functions. This review aims to provide ideas for exploring more diverse structures to improve UA pharmacological activity and increasing its biological yield to meet the industrial requirements by systematically reviewing the current research progress of UA. We first provides an overview of the pharmacological activities, acquisition methods and structural modifications of UA. Among them, we focused on the synthetic modifications of UA to yield valuable derivatives with enhanced therapeutic potential. Furthermore, harnessing the essential advances for green synthesis of UA and its derivatives by advent of metabolic engineering and synthetic biology are of great concern. In this regard, all pivotal advances for enhancing the production of UA have been discussed. In combination with the advantages of UA biosynthesis and transformation strategy, large-scale microbial production of UA is a promising platform for further exploration.

Cytochrome P450 Enzymes as Key Drivers of Alkaloid Chemical Diversification in Plants

Plants produce more than 20,000 nitrogen-containing heterocyclic metabolites called alkaloids. These chemicals serve numerous eco-physiological functions in the plants as well as medicines and psychedelic drugs for human for thousands of years, with the anti-cancer agent vinblastine and the painkiller morphine as the best-known examples. Cytochrome P450 monooxygenases (P450s) play a key role in generating the structural variety that underlies this functional diversity of alkaloids. Most alkaloid molecules are heavily oxygenated thanks to P450 enzymes' activities. Moreover, the formation and re-arrangement of alkaloid scaffolds such as ring formation, expansion, and breakage that contribute to their structural diversity and bioactivity are mainly catalyzed by P450s. The fast-expanding genomics and transcriptomics databases of plants have accelerated the investigation of alkaloid metabolism and many players behind the complexity and uniqueness of alkaloid biosynthetic pathways. Here we discuss recent discoveries of P450s involved in the chemical diversification of alkaloids and how these inform our approaches in understanding plant evolution and producing plant-derived drugs.

RNA Sequencing Reveals Rice Genes Involved in Male Reproductive Development under Temperature Alteration

Rice (Oryza sativa L.) is one of the most important food crops, providing food for nearly half of the world population. Rice grain yields are affected by temperature changes. Temperature stresses, both low and high, affect male reproductive development, resulting in yield reduction. Thermosensitive genic male sterility (TGMS) rice is sterile at high temperature and fertile at low temperature conditions, facilitating hybrid production, and is a good model to study effects of temperatures on male development. Semithin sections of the anthers of a TGMS rice line under low (fertile) and high (sterile) temperature conditions showed differences starting from the dyad stage, suggesting that genes involved in male development play a role during postmeiotic microspore development. Using RNA sequencing (RNA-Seq), transcriptional profiling of TGMS rice panicles at the dyad stage revealed 232 genes showing differential expression (DEGs) in a sterile, compared to a fertile, condition. Using qRT-PCR to study expression of 20 selected DEGs using panicles of TGMS and wild type rice plants grown under low and high temperature conditions, revealed that six out of the 20 selected genes may be unique to TGMS, while the other 14 genes showed common responses to temperatures in both TGMS and wild-type rice plants. The results presented here would be useful for further investigation into molecular mechanisms controlling TGMS and rice responses to temperature alteration.

Moonlighting in drug metabolism

Drug metabolizing enzymes catalyze the biotransformation of many of drugs and chemicals. The drug metabolizing enzymes are distributed among several evolutionary families and catalyze a range of detoxication reactions, including oxidation/reduction, conjugative, and hydrolytic reactions that serve to detoxify potentially toxic compounds. This detoxication function requires that drug metabolizing enzymes exhibit substrate promiscuity. In addition to their catalytic functions, many drug metabolizing enzymes possess functions unrelated to or in addition to catalysis. Such proteins are termed 'moonlighting proteins' and are defined as proteins with multiple biochemical or biophysical functions that reside in a single protein. This review discusses the diverse moonlighting functions of drug metabolizing enzymes and the roles they play in physiological functions relating to reproduction, vision, cell signaling, cancer, and transport. Further research will likely reveal new examples of moonlighting functions of drug metabolizing enzymes.

Molecular determinant of substrate binding and specificity of cytochrome P450 2J2

Cytochrome P450 2J2 (CYP2J2) is responsible for the epoxidation of endogenous arachidonic acid, and is involved in the metabolism of exogenous drugs. To date, no crystal structure of CYP2J2 is available, and the proposed structural basis for the substrate recognition and specificity in CYP2J2 varies with the structural models developed using different computational protocols. In this study, we developed a new structural model of CYP2J2, and explored its sensitivity to substrate binding by molecular dynamics simulations of the interactions with chemically similar fluorescent probes. Our results showed that the induced-fit binding of these probes led to the preferred active poses ready for the catalysis by CYP2J2. Divergent conformational dynamics of CYP2J2 due to the binding of each probe were observed. However, a stable hydrophobic clamp composed of residues I127, F310, A311, V380, and I487 was identified to restrict any substrate access to the active site of CYP2J2. Molecular docking of a series of compounds including amiodarone, astemizole, danazol, ebastine, ketoconazole, terfenadine, terfenadone, and arachidonic acid to CYP2J2 confirmed the role of those residues in determining substrate binding and specificity of CYP2J2. In addition to the flexibility of CYP2J2, the present work also identified other factors such as electrostatic potential in the vicinity of the active site, and substrate strain energy and property that have implications for the interpretation of CYP2J2 metabolism.

Cytochromes P450 (P450s): A review of the class system with a focus on prokaryotic P450s

Cytochromes P450 (P450s) are a large superfamily of heme-containing monooxygenases. P450s are found in all Kingdoms of life and exhibit incredible diversity, both at sequence level and also on a biochemical basis. In the majority of cases, P450s can be assigned into one of ten classes based on their associated redox partners, domain architecture and cellular localization. Prokaryotic P450s now represent a large diverse collection of annotated/known enzymes, of which many have great potential biocatalytic potential. The self-sufficient P450 classes (Class VII/VIII) have been explored significantly over the past decade, with many annotated and biochemically characterized members. It is clear that the prokaryotic P450 world is expanding rapidly, as the number of published genomes and metagenome studies increases, and more P450 families are identified and annotated (CYP families).

An overview of the factors playing a role in cytochrome P450 monooxygenase and ferredoxin interactions

Cytochrome P450 monooxygenases (CYPs/P450s) are heme-thiolate proteins that are ubiquitously present in organisms, including non-living entities such as viruses. With the exception of self-sufficient P450s, all other P450 enzymes need electrons to perform their enzymatic activity and these electrons are supplied by P450 redox proteins. Different types of P450 redox proteins can be found in organisms and are classified into different classes. Bacterial P450s (class I) receive electrons from ferredoxins which are iron-sulfur cluster proteins. The presence of more than one copy and different types of ferredoxins within a bacterial species poses fundamental questions about the selectivity of P450s and ferredoxins in relation to each other. Apart from transferring electrons, ferredoxins have also been found to modulate P450 functions. Achieving an understanding of the interaction between ferredoxins and P450s is required to harness their biotechnological potential for designing a universal electron transfer protein. A brief overview of factors playing a role in ferredoxin and P450 interactions is presented in this review article.

Altered expression of cytochrome P450 enzymes involved in metabolism of androgens and vitamin D in the prostate as a risk factor for prostate cancer

Prostate cancer is the most common malignant disease among men. The signaling pathways, regulated by the androgen and vitamin D receptors, play a key role in prostate cancer. The intracellular level of androgens and vitamin D determines not only receptor functionality, but also the efficacy of cellular processes regulated by them (cell proliferation, apoptosis, differentiation etc.). It is known that several androgen-metabolizing P450s (CYP3A4/5/43 and CYP2B6) and P450 enzymes (CYP2R1, CYP27A1, CYP27B1, CYP24A1, CYP3A4, CYP2J2), which are necessary for vitamin D metabolism, are expressed in the prostate. It was shown that alterations in an expression pattern of the certain cytochrome P450s might lead to the development of castration-resistant cancer (CYP3A4, CYP2J2, CYP24A1), and to chemo-resistance (CYP3A4, CYP3A5, CYP2B6) and early mortality (CYP2B6, CYP27A1, CYP24A1). Moreover, steroidogenic CYPs (CYP17A1, CYP11A1) are not expressed in normal prostate tissue. Alterations in their expression levels in steroidogenic tissues are closely associated with carcinogenesis, and, most importantly, with the development of aggressive forms of prostate cancer. Hence, it is important, to study how expression of CYPs in the prostate might be regulated, to understand the mechanisms of disease development and to improve the effectiveness of therapy. Several CYPs (CYP3A43, CYP2B6, CYP27A1, CYP24A1) can be considered as prognostic and diagnostic markers of prostate cancer. To propose personalized treatment, individual differences in CYP expression should be taken into account.

Structural insight into the electron transfer pathway of a self-sufficient P450 monooxygenase

Cytochrome P450 monooxygenases are versatile heme-thiolate enzymes that catalyze a wide range of reactions. Self-sufficient cytochrome P450 enzymes contain the redox partners in a single polypeptide chain. Here, we present the crystal structure of full-length CYP116B46, a self-sufficient P450. The continuous polypeptide chain comprises three functional domains, which align well with the direction of electrons traveling from FMN to the heme through the [2Fe-2S] cluster. FMN and the [2Fe-2S] cluster are positioned closely, which facilitates efficient electron shuttling. The edge-to-edge straight-line distance between the [2Fe-2S] cluster and heme is approx. 25.3 Å. The role of several residues located between the [2Fe-2S] cluster and heme in the catalytic reaction is probed in mutagenesis experiments. These findings not only provide insights into the intramolecular electron transfer of self-sufficient P450s, but are also of interest for biotechnological applications of self-sufficient P450s.

Self-sufficient cytochrome P450 monooxygenases, which contain all redox partners in a single polypeptide chain, are of interest for biotechnological applications. Here, the authors present the crystal structure of full-length Thermobispora bispora CYP116B46 and discuss the potential electron transfer pathway.

Three-Dimensional Visualization of APEX2-Tagged Erg11 in Saccharomyces cerevisiae Using Focused Ion Beam Scanning Electron Microscopy

The determination of the exact location of a protein in the cell is essential to the understanding of biological processes. Here, we report for the first time the visualization of a protein of interest in Saccharomyces cerevisiae using focused ion beam scanning electron microscopy (FIB-SEM). As a proof of concept, the integral endoplasmic reticulum (ER) membrane protein Erg11 has been C-terminally tagged with APEX2, which is an engineered peroxidase that catalyzes an electron-dense deposition of 3,3'-diaminobenzidine (DAB), as such marking the location of the fused protein of interest in electron microscopic images. As DAB is unable to cross the yeast cell wall to react with APEX2, cell walls have been partly removed by the formation of spheroplasts. This has resulted in a clear electron-dense ER signal for the Erg11 protein using FIB-SEM. With this study, we have validated the use of the APEX2 tag for visualization of yeast proteins in electron microscopy. Furthermore, we have introduced a methodology that enables precise and three-dimensional (3D) localization studies in yeast, with nanometer resolution and without the need for antibody staining. Because of these properties, the described technique can offer valuable information on the molecular functions of studied proteins.IMPORTANCE With this study, we have validated the use of the APEX2 tag to define the localization of proteins in the model yeast S. cerevisiae As such, FIB-SEM can identify the exact 3D location of a protein of interest in the cell with nanometer-scale resolution. Such detailed imaging could provide essential information on the elucidation of various biological processes. APEX2, which adds electron density to a fused protein of interest upon addition of the substrate DAB, originally was used in mammalian studies. With this study, we expand its use to protein localization studies in one of the most important models in molecular biology.

Physiological regulation of reactive oxygen species in organisms based on their physicochemical properties

Oxidative stress is recognized as free radical dyshomeostasis, which has damaging effects on proteins, lipids and DNA. However, during cell differentiation and proliferation and other normal physiological processes, free radicals play a pivotal role in message transmission and are considered important messengers. Organisms maintain free radical homeostasis through a sophisticated regulatory system in which these "2-faced" molecules play appropriate roles under physiological and pathological conditions. Reactive oxygen species (ROS), including a large number of free radicals, act as redox signalling molecules in essential cellular signalling pathways, including cell differentiation and proliferation. However, excessive ROS levels can induce oxidative stress, which is an important risk factor for diabetes, cancer and cardiovascular disease. An overall comprehensive understanding of ROS is beneficial for understanding the pathogenesis of certain diseases and finding new therapeutic treatments. This review primarily focuses on ROS cellular localization, sources, chemistry and molecular targets to determine how to distinguish between the roles of ROS as messengers and in oxidative stress.

The Biosynthesis of Enzymatically Oxidized Lipids

Enzymatically oxidized lipids are a specific group of biomolecules that function as key signaling mediators and hormones, regulating various cellular and physiological processes from metabolism and cell death to inflammation and the immune response. They are broadly categorized as either polyunsaturated fatty acid (PUFA) containing (free acid oxygenated PUFA "oxylipins", endocannabinoids, oxidized phospholipids) or cholesterol derivatives (oxysterols, steroid hormones, and bile acids). Their biosynthesis is accomplished by families of enzymes that include lipoxygenases (LOX), cyclooxygenases (COX), cytochrome P450s (CYP), and aldo-keto reductases (AKR). In contrast, non-enzymatically oxidized lipids are produced by uncontrolled oxidation and are broadly considered to be harmful. Here, we provide an overview of the biochemistry and enzymology of LOXs, COXs, CYPs, and AKRs in humans. Next, we present biosynthetic pathways for oxylipins, oxidized phospholipids, oxysterols, bile acids and steroid hormones. Last, we address gaps in knowledge and suggest directions for future work.

Cytochrome P450: genotype to phenotype

The cytochromes P450 comprise a family of enzymes that are responsible for around three-quarters of all drug metabolism reactions that occur in human populations. Many isoforms of cytochrome P450 exist but most reactions are undertaken by CYP2C9, CYP2C19, CYP2D6 and CYP3A4. This brief review focusses on the first three isozymes which exhibit polymorphism of phenotype.If there is a wide variation in drug metabolising capacity within the population, this may precipitate clinical consequences and influence the drug treatment of patients. Such problems range from a lack of efficacy to unanticipated toxicity. In order to minimise untoward events and "personalise" a patient's treatment, efforts have been made to discover an individual's drug metabolism status. This requires knowledge of the subject's phenotype at the time of clinical treatment. Since such testing is difficult, time-consuming and costly, the simpler approach of genotyping has been advocated.However, the correlation between genotype and phenotype is not good, with values of up to 50% misprediction being reported. Genotype-assisted forecasts cannot therefore be used with confidence to replace actual phenotype measurements. Obfuscating factors discussed include gene splicing, single nucleotide polymorphisms, epigenetics and microRNA, transcription regulation and multiple gene copies.

Differential Expression of Cytochrome P450 CYP6 Genes in the Brown Marmorated Stink Bug, Halyomorpha halys (Hemiptera: Pentatomidae)

Cytochrome (CYP) P450s are a superfamily of enzymes that detoxify xenobiotics and regulate numerous physiological processes in insects. The genomes of phytophagous insects usually contain large numbers of P450s, especially within the CYP3 clan. Within this clan, CYP6 subfamily members help detoxify plant host secondary metabolites. In this study, we analyzed three CYP6 genes in the highly polyphagous invasive pest, Halyomorpha halys (Stål), commonly known as brown marmorated stink bug. We characterized and validated the expression of HhCYP6BQ27, HhCYP6BK13, and HhCYP6BK24 among sexes, tissues (gut, fat body, and Malpighian tubules) and hosts (apple, corn, soybean). Sequence characterization by amino acid alignments confirmed the presence of conserved motifs typical of the P450 superfamily. No significant differences existed in gene expression among sexes or when fed different hosts, suggesting that these transcripts might have broad substrate specificities. However, significant differences in gene expression were observed among the tissues studied and were gene-dependent. Collectively, the results show that H. halys differentially expressed CYP6 genes among tissues, which may be related to important and specific physiological functions. This study has increased our understanding of H. halys biology that can be useful for functional studies and can potentially be exploited in developing sustainable pest management strategies.

Plasma membrane localization of CYP4Z1 and CYP19A1 and the detection of anti-CYP19A1 autoantibodies in humans

It is thought that autoantibody (aAb) production can be caused by (aberrant) protein targeting to the plasma surface of cells. We recently demonstrated the presence of the human cytochrome P450 enzyme CYP4Z1 on the plasma membrane of MCF-7 breast cancer cells and the detection of high titers of anti-CYP4Z1 aAbs in breast cancer patients, but not in healthy controls. In the present study we show that cells of the normal breast cell line MCF-10A do not display CYP4Z1 on their surface. By contrast, we detected CYP19A1 (aromatase) on the plasma membrane of both cell lines. Interestingly, the presence of CYPs on the cell surface did not correlate with their relative expression levels in these cell lines. Indirect ELISA experiments demonstrated the presence of anti-CYP19A1 aAbs in female breast cancer patient sera as well as in male and female controls, respectively; aAb titers in all three groups varied considerably and overall, the results obtained for each group were not significantly different from those of either of the other two groups. Based on these data we propose the hypothesis that CYP translocation to the plasma membrane, but not the intracellular expression level, is the crucial precondition for the generation of anti-CYP aAbs.

A Novel Multiplex PCR-RFLP Method for Simultaneous Genotyping of CYP3A4*4 A>G, CYP3A4*18B G>A and CYP3A4*22 C>T

BACKGROUND

Cytochrome P450 3A enzymes exhibit a variety of physiological roles and have been reported to be the most predominant enzymes involved in drugs metabolism. Single nucleotide polymorphisms (SNPs) in the genes that code for these enzymes may result in functional changes that affect enzyme activity. CYP3A4 is an important enzyme in the metabolism of many important drugs used in the treatment of breast cancer.

METHODS

A total of 94 post-menopausal breast cancer patients were recruited for the study and their DNA was isolated for polymerase chain reaction (PCR). The primers were designed using Primer3 software with primer specificities checked via the Basic Local Alignment Tool (BLAST) database. The primer specificity, functionality and annealing temperature were first investigated using uniplex PCR protocols, followed by a single multiplex polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. The digested amplification fragments were analysed by gel electrophoresis and subsequently validated by sequencing.

RESULTS

A multiplex PCR-RFLP method was successfully developed for simultaneous detection of CYP3A4*4, CYP3A4*18B and CYP3A4*22 in a population of post-menopausal breast cancer patients.

CONCLUSION

The technique is simple, cost-effective, time-saving and can be routinely applied in the identification of SNPs and determination of allelic and genotypic frequencies of CYP3A4*4, CYP3A4*18B and CYP3A4*22.

Comparative analyses and structural insights of the novel cytochrome P450 fusion protein family CYP5619 in Oomycetes

Phylogenetic and structural analysis of P450 proteins fused to peroxidase/dioxygenase has not been reported yet. We present phylogenetic and in silico structural analysis of the novel P450 fusion family CYP5619 from the deadliest fish pathogenic oomycete, Saprolegnia diclina. Data-mining and annotation of CYP5619 members revealed their unique presence in oomycetes. CYP5619 members have the highest number of conserved amino acids among eukaryotic P450s. The highest number of conserved amino acids (78%) occurred in the peroxidase/dioxygenase domain compared to the P450 domain (22%). In silico structural analysis using a high-quality CYP5619A1 model revealed that CYP5619A1 has characteristic P450 structural motifs including EXXR and CXG. However, the heme-binding domain (CXG) in CYP5619 members was found to be highly degenerated. The in silico substrate binding pattern revealed that CYP5619A1 have a high affinity to medium chain fatty acids. Interestingly, the controlling agent of S. diclina malachite green was predicted to have the highest binding affinity, along with linoleic acid. However, unlike fatty acids, none of the active site amino acids formed hydrogen bonds with malachite green. The study’s results will pave the way for assessing CYP5619A1’s role in S. diclina physiology, including the nature of malachite green binding.

Strategies for the construction of insect P450 fusion enzymes

Cytochrome P450 monooxygenases (P450s) are ubiquitous enzymes with a broad substrate spectrum. Insect P450s are known to catalyze reactions such as the detoxification of insecticides and the synthesis of hydrocarbons, which makes them useful for many industrial processes. Unfortunately, it is difficult to utilize P450s effectively because they must be paired with cytochrome P450 reductases (CPRs) to facilitate electron transfer from reduced nicotinamide adenine dinucleotide phosphate (NADPH). Furthermore, eukaryotic P450s and CPRs are membrane-anchored proteins, which means they are insoluble and therefore difficult to purify when expressed in their native state. Both challenges can be addressed by creating fusion proteins that combine the P450 and CPR functions while eliminating membrane anchors, allowing the production and purification of soluble multifunctional polypeptides suitable for industrial applications. Here we discuss several strategies for the construction of fusion enzymes combining insect P450 with CPRs.

The Hinge Segment of Human NADPH-Cytochrome P450 Reductase in Conformational Switching: The Critical Role of Ionic Strength

NADPH-cytochrome P450 reductase (CPR) is a redox partner of microsomal cytochromes P450 and is a prototype of the diflavin reductase family. CPR contains 3 distinct functional domains: a FMN-binding domain (acceptor reduction), a linker (hinge), and a connecting/FAD domain (NADPH oxidation). It has been demonstrated that the mechanism of CPR exhibits an important step in which it switches from a compact, closed conformation (locked state) to an ensemble of open conformations (unlocked state), the latter enabling electron transfer to redox partners. The conformational equilibrium between the locked and unlocked states has been shown to be highly dependent on ionic strength, reinforcing the hypothesis of the presence of critical salt interactions at the interface between the FMN and connecting FAD domains. Here we show that specific residues of the hinge segment are important in the control of the conformational equilibrium of CPR. We constructed six single mutants and two double mutants of the human CPR, targeting residues G240, S243, I245 and R246 of the hinge segment, with the aim of modifying the flexibility or the potential ionic interactions of the hinge segment. We measured the reduction of cytochrome c at various salt concentrations of these 8 mutants, either in the soluble or membrane-bound form of human CPR. All mutants were found capable of reducing cytochrome c yet with different efficiency and their maximal rates of cytochrome c reduction were shifted to lower salt concentration. In particular, residue R246 seems to play a key role in a salt bridge network present at the interface of the hinge and the connecting domain. Interestingly, the effects of mutations, although similar, demonstrated specific differences when present in the soluble or membrane-bound context. Our results demonstrate that the electrostatic and flexibility properties of the hinge segment are critical for electron transfer from CPR to its redox partners.

Molecular cloning and 3D model of first cytochrome P450 from CYP3A subfamily in saltwater crocodile (Crocodylus porosus)

Cytochrome P450s (CYPs) play critical role in oxidative metabolism of numerous xenobiotics and endogenous compounds. The first CYP3A subfamily member in saltwater crocodile has been cloned and modelled for three-dimensional (3D) structure. The full-length cDNA was obtained employing reverse transcription polymerase chain reaction (RT-PCR) strategy and rapid amplification of cDNA ends (RACE). The cDNA sequence of 1659 nucleotides includes 132 nucleotides from 5' untranslated region (UTR), an open reading frame of 1527 nucleotides encoding 509 amino acids designated as CYP3A163. The alignment of CYP3A163 sequence with CYP3A subfamily across the lineages exhibit the loss of 1 residue in birds and 7 residues in mammals in comparison to reptiles suggesting the adaptation processes during evolution. The amino acid identity of CYP3A163 with Alligator mississippiensis CYP3A77 and Homo sapiens CYP3A4 is 91% and 62% respectively. The 3D structure of CYP3A163 modelled using human CYP3A4 structure as a template with Phyre² software, represents high similarity with its functionally important motifs and catalytic domain. Both sequence and structure of CYP3A163 display the common and conserved features of CYP3A subfamily. Overall, this study provides primary molecular and structural data of CYP3A163 required to investigate the xenobiotic metabolism in saltwater crocodiles.

Characterization of Prostate Cancer in a Functional Eunuch

BACKGROUND

Eunuchs rarely, if ever, develop prostate cancer (CaP). This article reports on a 62-year-old functional eunuch from prepubertal mumps orchitis who developed clinically localized CaP.

METHODS

Serum and CaP and benign prostate tissue androgen levels were measured using a validated liquid chromatography-tandem mass spectrometry assay. The assay measures testosterone; dihydrotestosterone (DHT); the adrenal androgens, androstenedione and dehydroepiandrosterone; and the androgen metabolites, androsterone and androstanedione. Gene and protein expression levels of androgen metabolism enzymes, and androgen receptor and androgen-regulated genes were measured using quantitative reverse-transcription polymerase chain reaction and immunohistochemistry, respectively.

RESULTS

Intracrine androgen metabolism produced tissue DHT when serum and tissue testosterone levels were castrate and undetectable, respectively. Androgen receptor, androgen-regulated, and androgen metabolism enzyme genes were expressed but at lower levels in CaP than benign tissues.

CONCLUSIONS

DHT was synthesized using the primary backdoor androgen metabolism pathway and not using androstenedione or dehydroepiandrosterone via the frontdoor or secondary backdoor pathways.

Genome content, metabolic pathways and biotechnological potential of the psychrophilic Arctic bacterium Psychrobacter sp. DAB_AL43B, a source and a host of novel Psychrobacter-specific vectors

Psychrobacter sp. DAB_AL43B, isolated from ornithogenic soil collected on the Arctic island of Spitsbergen, is a newly sequenced psychrophilic strain susceptible to conjugation and electrotransformation. Its genome consists of a circular chromosome (3.3 Mb) and four plasmids (4.4-6.4kb). In silico genome mining and microarray-based phenotypic analysis were performed to describe the metabolic potential of this strain and identify possible biotechnological applications. Metabolic reconstruction indicated that DAB_AL43B prefers low-molecular-weight carboxylates and amino acids as carbon and energy sources. Genetic determinants of heavy-metal resistance, anthracene degradation and possible aerobic denitrification were also identified. Comparative analyses revealed a relatively close relationship between DAB_AL43B and other sequenced Psychrobacter species. In addition, the plasmids of this strain were used as the basis for the construction of Escherichia coli-Psychrobacter spp. shuttle vectors. Taken together, the results of this work suggest that DAB_AL43B is a promising candidate as a new model strain for studies on Psychrobacter spp.

Cytochromes P450 for natural product biosynthesis in Streptomyces: sequence, structure, and function

Covering: up to January 2017Cytochrome P450 enzymes (P450s) are some of the most exquisite and versatile biocatalysts found in nature. In addition to their well-known roles in steroid biosynthesis and drug metabolism in humans, P450s are key players in natural product biosynthetic pathways. Natural products, the most chemically and structurally diverse small molecules known, require an extensive collection of P450s to accept and functionalize their unique scaffolds. In this review, we survey the current catalytic landscape of P450s within the Streptomyces genus, one of the most prolific producers of natural products, and comprehensively summarize the functionally characterized P450s from Streptomyces. A sequence similarity network of >8500 P450s revealed insights into the sequence-function relationships of these oxygen-dependent metalloenzymes. Although only ∼2.4% and <0.4% of streptomycete P450s have been functionally and structurally characterized, respectively, the study of streptomycete P450s involved in the biosynthesis of natural products has revealed their diverse roles in nature, expanded their catalytic repertoire, created structural and mechanistic paradigms, and exposed their potential for biomedical and biotechnological applications. Continued study of these remarkable enzymes will undoubtedly expose their true complement of chemical and biological capabilities.

Engineering of versatile redox partner fusions that support monooxygenase activity of functionally diverse cytochrome P450s

Most bacterial cytochrome P450 monooxygenases (P450s or CYPs) require two redox partner proteins for activity. To reduce complexity of the redox chain, the Bacillus subtilis flavodoxin YkuN (Y) was fused to the Escherichia coli flavodoxin reductase Fpr (R), and activity was tuned by placing flexible (GGGGS)_n or rigid ([E/L]PPPP)_n linkers (n = 1–5) in between. P-linker constructs typically outperformed their G-linker counterparts, with superior performance of YR-P5, which carries linker ([E/L]PPPP)₅. Molecular dynamics simulations demonstrated that ([E/L]PPPP)_n linkers are intrinsically rigid, whereas (GGGGS)_n linkers are highly flexible and biochemical experiments suggest a higher degree of separation between the fusion partners in case of long rigid P-linkers. The catalytic properties of the individual redox partners were best preserved in the YR-P5 construct. In comparison to the separate redox partners, YR-P5 exhibited attenuated rates of NADPH oxidation and heme iron (III) reduction, while coupling efficiency was improved (28% vs. 49% coupling with B. subtilis CYP109B1, and 44% vs. 50% with Thermobifida fusca CYP154E1). In addition, YR-P5 supported monooxygenase activity of the CYP106A2 from Bacillus megaterium and bovine CYP21A2. The versatile YR-P5 may serve as a non-physiological electron transfer system for exploitation of the catalytic potential of other P450s.

In vitro characterization of CYP102G4 from Streptomyces cattleya: A self-sufficient P450 naturally producing indigo

Self-sufficient CYP102As possess outstanding hydroxylating activity to fatty acids such as myristic acid. Other CYP102 subfamily members share substrate specificity of CYP102As, but, occasionally, unusual characteristics of its own subfamily have been found. In this study, only one self-sufficient cytochrome P450 from Streptomyces cattleya was renamed from CYP102A_scat to CYP102G4, purified and characterized. UV-Vis spectrometry pattern, FAD/FMN analysis, and protein sequence comparison among CYP102s have shown that CYP102 from Streptomyces cattleya belongs to CYP102G subfamily. It showed hydroxylation activity toward fatty acids generating ω-1, ω-2, and ω-3-hydroxyfatty acids, which is similar to the general substrate specificity of CYP102 family. Unexpectedly, however, expression of CYP102G4 showed indigo production in LB medium batch flask culture, and high catalytic activity (k_cat/K_m) for indole was measured as 6.14±0.10min^-1mM^-1. Besides indole, CYP102G4 was able to hydroxylate aromatic compounds such as flavone, benzophenone, and chloroindoles. Homology model has shown such ability to accept aromatic compounds is due to its bigger active site cavity. Unlike other CYP102s, CYP102G4 did not have biased cofactor dependency, which was possibly determined by difference in NAD(P)H binding residues (Ala984, Val990, and Tyr1064) compared to CYP102A1 (Arg966, Lys972 and Trp1046). Overall, a self-sufficient CYP within CYP102G subfamily was characterized using purified enzymes, which appears to possess unique properties such as an only prokaryotic CYP naturally producing indigo.

Assessing the identity and expression level of the cytochrome P450 20A1 (CYP20A1) gene in the BPA-, BDE-47, and WAF-exposed copepods Tigriopus japonicus and Paracyclopina nana

CYP20A1 is a member of the cytochrome P450 (CYP) superfamily, identified as an orphan P450 without any assigned biological function; hence, its continued status as an "orphan" gene. In order to address this shortcoming in our understanding of this superfamily, we sought to characterize the CYP20A1 gene in the copepods Tigriopus japonicus (Tj-CYP20A1) and Paracyclopina nana (Pn-CYP20A1) at their mRNA transcriptional level. We assessed the response of this gene's expression in various developmental stages and in response to treatment with bisphenol A (BPA), 2, 2', 4, 4'-tetrabromodiphenyl ether (BDE-47), and water accommodated fractions (WAFs) of crude oil. As shown in the vertebrate CYP20A1, both Tj-CYP20A1 and Pn-CYP20A1 contained characteristic conserved motifs and domain regions (I helix, K helix and heme-binding motifs) with unusual amino acid sequences apparent in their gene structure. Also molecular characterization of the putative responsive elements in the promoter regions was performed. We observed transcriptional up-regulation of these genes during post-embryonic developmental stages including sex-specific up-regulation in adults. In addition, concentration- and time-dependent mRNA transcripts in response to xenobiotics (BPA, BDE-47, and WAFs) were seen. This study focuses on the molecular elucidation of CYP20A1 genes and their interactions with xenobiotics in the copepods T. japonicus and P. nana that provides important insight into the biological importance of CYP20A1 in invertebrates.

Identification and analysis of a processed cytochrome P450 pseudogene of the disease vector Aedes aegypti

OBJECTIVE

To clone cytochrome P450 from Aedes aegypti (Ae. aegypti) and determine the characteristics using bioinformatics tools.

METHODS

Cytochrome P450 of Ae. aegypti was amplified using polymerase chain reaction, cloned and sequenced. Evolutionary relationship of the sequence was inferred and bioinformatics tools were used to predict subcellular localisation, signal peptide, transmembrane helix, phosphorylation, O-glycosylation, secondary and tertiary structures of the deduced protein.

RESULTS

Polymerase chain reaction rather amplified a cytochrome P450 pseudogene which was named CYP4H44P (GenBank accession number KF779932). The pseudogene has 1537 nucleotides and an open reading frame of 335 amino acids containing cytochrome P450 motifs except the WxxxR motif. It is highly homologous to CYP4H28 and CYP4H28v2. Phylogenetic analysis and evolutionary divergence showed strong clustering with CYP4H28 alleles and least divergence from the alleles respectively. The deduced protein was predicted to be found in the cytoplasm and likely to be phosphorylated but devoid of signal peptide, transmembrane helix and O-glycosylated sites. The secondary and tertiary structures were also generated.

CONCLUSIONS

A cytochrome P450 pseudogene, CYP4H44P was cloned from Ae. aegypti. The pseudogene is homologous with CYP4H28 alleles and seems to have recently diverged from this group. Isolating this pseudogene is an important step for evaluating its biological role in the mosquito and for the evolutionary analysis of Ae. aegypti CYPs.

Methane-Oxidizing Enzymes: An Upstream Problem in Biological Gas-to-Liquids Conversion

Biological conversion of natural gas to liquids (Bio-GTL) represents an immense economic opportunity. In nature, aerobic methanotrophic bacteria and anaerobic archaea are able to selectively oxidize methane using methane monooxygenase (MMO) and methyl coenzyme M reductase (MCR) enzymes. Although significant progress has been made toward genetically manipulating these organisms for biotechnological applications, the enzymes themselves are slow, complex, and not recombinantly tractable in traditional industrial hosts. With turnover numbers of 0.16-13 s(-1), these enzymes pose a considerable upstream problem in the biological production of fuels or chemicals from methane. Methane oxidation enzymes will need to be engineered to be faster to enable high volumetric productivities; however, efforts to do so and to engineer simpler enzymes have been minimally successful. Moreover, known methane-oxidizing enzymes have different expression levels, carbon and energy efficiencies, require auxiliary systems for biosynthesis and function, and vary considerably in terms of complexity and reductant requirements. The pros and cons of using each methane-oxidizing enzyme for Bio-GTL are considered in detail. The future for these enzymes is bright, but a renewed focus on studying them will be critical to the successful development of biological processes that utilize methane as a feedstock.

In Situ Proteolysis for Crystallization of Membrane Bound Cytochrome P450 17A1 and 17A2 Proteins from Zebrafish

Fish and human cytochrome P450 (P450) 17A1 catalyze both steroid 17α-hydroxylation and 17α,20-lyase reactions. Fish P450 17A2 catalyzes only 17α-hydroxylation. Both enzymes are microsomal-type P450s, integral membrane proteins that bind to the membrane through their N-terminal hydrophobic segment, the signal anchor sequence. The presence of this N-terminal region renders expression of full-length proteins challenging or impossible. For some proteins, variable truncation of the signal anchor sequence precludes expression or results in poor expression levels. To crystallize P450 17A1 and 17A2 in order to gain insight into their different activities, we used an alternative N-terminal sequence to boost expression together with in situ proteolysis. Key features of our approach to identify crystallizable P450 fragments were the use of an N-terminal leader sequence, a screen composed of 12 proteases to establish optimal cleavage, variations of protease concentration in combination with an SDS-PAGE assay, and analysis of the resulting fragments using Edman sequencing. Described in this unit are protocols for vector preparation, expression, purification, and in situ proteolytic crystallization of two membrane-bound P450 proteins.