Biocatalysis and substrate chemodiversity: Adaptation of aerobic living organisms to their chemical environment

Functional Study on Cytochrome P450 in Response to L(-)-Carvone Stress in Bursaphelenchus xylophilus

Bursaphelenchus xylophilus (PWN) causes pine wilt disease (PWD), which is one of the most devastating pine diseases worldwide. Cytochrome P450 (CYP) catalyzes the biosynthetic metabolism of terpenoids and plays an important role in the modification of secondary metabolites in all living organisms. We investigated the molecular characteristics and biological functions of Bx-cyp29A3 in B. xylophilus. The bioinformatics analysis results indicated that Bx-cyp29A3 has a transmembrane domain and could dock with L(-)-carvone. The gene expression pattern indicated that Bx-cyp29A3 was expressed in 0.2, 0.4, 0.6, 0.8, and 1.0 mg/mL L(-)-carvone solutions. The Bx-cyp29A3 expression increased in a dose-dependent manner and peaked at 24 h of exposure when the L(-)-carvone solution concentration was 0.8 mg/mL. However, the gene expression peaked at 0.6 mg/mL after 36 h. Furthermore, RNA interference (RNAi) indicated that Bx-cyp29A3 played an essential role in the response to L(-)-carvone. The mortality rates of the Bx-cyp29A3 knockdown groups were higher than those of the control groups in the 0.4, 0.6, 0.8, and 1.0 mg/mL carvone solutions after 24 h of exposure or 36 h of exposure. In summary, bioinformatics provided the structural characteristics and conserved sequence properties of Bx-cyp29A3 and its encoded protein, which provided a target gene for the study of the P450 family of B. xylophilus. Gene silencing experiments clarified the function of Bx-cyp29A3 in the immune defense of B. xylophilus. This study provides a basis for the screening of new molecular targets for the prevention and management of B. xylophilus.

Rhodamine B oxidation promoted by P450-bioinspired Jacobsen catalysts/cellulose systems

P450-bioinspired Jacobsen/Cell(NEt2) catalysts have been applied in RhB dye oxidation, which is used illegally in food industries of some countries.

Immobilized Lignin Peroxidase-Like Metalloporphyrins as Reusable Catalysts in Oxidative Bleaching of Industrial Dyes

Synthetic and bioinspired metalloporphyrins are a class of redox-active catalysts able to emulate several enzymes such as cytochromes P450, ligninolytic peroxidases, and peroxygenases. Their ability to perform oxidation and degradation of recalcitrant compounds, including aliphatic hydrocarbons, phenolic and non-phenolic aromatic compounds, sulfides, and nitroso-compounds, has been deeply investigated. Such a broad substrate specificity has suggested their use also in the bleaching of textile plant wastewaters. In fact, industrial dyes belong to very different chemical classes, being their effective and inexpensive oxidation an important challenge from both economic and environmental perspective. Accordingly, we review here the most widespread synthetic metalloporphyrins, and the most promising formulations for large-scale applications. In particular, we focus on the most convenient approaches for immobilization to conceive economical affordable processes. Then, the molecular routes of catalysis and the reported substrate specificity on the treatment of the most diffused textile dyes are encompassed, including the use of redox mediators and the comparison with the most common biological and enzymatic alternative, in order to depict an updated picture of a very promising field for large-scale applications.

Immobilization of metalloporphyrin on a silica shell with bimetallic oxide core for ethylbenzene oxidation

In this study, metalloporphyrin has been immobilized on a core–shell structured SiO₂@CeO₂ doped with transition metals such as Fe, Cu, Co and Mn.

[Metabolism of xenobiotics: beneficial and adverse effects]

The systems developed by living organisms for the metabolism of xenobiotics play a key role in the adaptation of living species to their chemical environment. Recent data about mammalian cytochrome P450 structures have led to a better understanding of the molecular basis for the adaptability of these enzymes to xenobiotics exhibiting highly variable structures. The action of these enzymes on xenobiotics leads to other beneficial effects such as the bioactivation of some drugs, but also to adverse effects with the formation of aggressive metabolites for the cell that are responsible for the appearance of many toxicities.

Brief historical overview and recent progress on cytochromes P450: adaptation of aerobic organisms to their chemical environment and new mechanisms of prodrug bioactivation

The present brief overview of the history of the development of our knowledge on cytochromes P450 (P450s) illustrates the spectacular progress that have been made on P450 mechanisms and structures especially during these last 20 years. Recently published structures of mammalian P450-substrate complexes have shown the great diversity of size, shape, and binding modes that are offered by the conformationally flexible substrate binding sites of xenobiotic-metabolizing P450s. They have also shown that these binding sites can adapt themselves to the great structural diversity of xenobiotics, to facilitate their oxidation and elimination. Our present detailed knowledge of the mechanisms and chemistry of P450s allows us to understand, at the molecular level, the origin of the various consequences of P450-dependent metabolism of drugs in pharmacology and toxicology. This is here illustrated by recent data on the detailed mechanism of bioactivation of the anti-thrombotic prodrugs ticlopidine, clopidogrel, and prasugrel.

Conformational plasticity and structure/function relationships in cytochromes P450

The cytochrome P450s are a superfamily of enzymes that are found in all kingdoms of living organisms, and typically catalyze the oxidative addition of atomic oxygen to an unactivated C-C or C-H bond. Over 8000 nonredundant sequences of putative and confirmed P450 enzymes have been identified, but three-dimensional structures have been determined for only a small fraction of these. While all P450 enzymes for which structures have been determined share a common global fold, the flexibility and modularity of structure around the active site account for the ability of P450 enzymes to accommodate a vast number of structurally dissimilar substrates and support a wide range of selective oxidations. In this review, known P450 structures are compared, and some structural criteria for prediction of substrate selectivity and reaction type are suggested. The importance of dynamic processes such as redox-dependent and effector-induced conformational changes in determining catalytic competence and regio- and stereoselectivity is discussed, and noncrystallographic methods for characterizing P450 structures and dynamics, in particular, mass spectrometry and nuclear magnetic resonance spectroscopy are reviewed.

Porphyrin-kaolinite as efficient catalyst for oxidation reactions

The preparation, characterization, and application in oxidation reactions of new biomimetic catalysts are reported. Brazilian Sao Simao kaolinite clay has been functionalized with [meso-tetrakis(pentafluorophenyl)porphinato]iron(III), Fe(TPFPP). To obtain the functionalized clay, the natural clay was purified by dispersion-sedimentation, expanded by insertion of dimethyl sulfoxide (DMSO), and functionalized with amino groups by substitution of DMSO with ethanolamine. These previous steps allowed clay functionalization with Fe(TPFPP), leading to a layered material with a basal spacing of 10.73 A. Clay functionalization with the porphyrin was confirmed by formation of the secondary amine, as demonstrated by FTIR bands at 3500-3700 cm(-1). UV-vis spectroscopy revealed a red shift in the Soret band of the iron porphyrin in the functionalized material as compared to the parent iron porphyrin catalyst in solution, indicating Fe(III)P --> Fe(II)P reduction. The catalytic performance of the functionalized clay was evaluated in the epoxidation of cyclooctene, with complete selectivity for the epoxide (100% epoxide yield), and ketonization of cyclohexane, cyclohexanone being the major product. The novel catalyst was also evaluated in the Baeyer-Villiger (BV) oxidation of cyclohexanone, with 85% conversion of cyclohexanone in epsilon-caprolactone, with total selectivity to epsilon-caprolactone.

Cooperative properties of cytochromes P450

Cytochromes P450 form a large and important class of heme monooxygenases with a broad spectrum of substrates and corresponding functions, from steroid hormone biosynthesis to the metabolism of xenobiotics. Despite decades of study, the molecular mechanisms responsible for the complex non-Michaelis behavior observed with many members of this superfamily during metabolism, often termed 'cooperativity', remain to be fully elucidated. Although there is evidence that oligomerization may play an important role in defining the observed cooperativity, some monomeric cytochromes P450, particularly those involved in xenobiotic metabolism, also display this behavior due to their ability to simultaneously bind several substrate molecules. As a result, formation of distinct enzyme-substrate complexes with different stoichiometry and functional properties can give rise to homotropic and heterotropic cooperative behavior. This review aims to summarize the current understanding of cooperativity in cytochromes P450, with a focus on the nature of cooperative effects in monomeric enzymes.

Metalloporphyrin-based oxidation systems: from biomimetic reactions to application in organic synthesis

The oxidation of organic substrates catalyzed by metalloporphyrins constitutes a major class of biomimetic oxidation reactions used in modern synthetic chemistry. Ruthenium porphyrins are among the most extensively studied metalloporphyrin oxidation catalysts. This article provides a brief outline of the metalloporphyrin-based oxidation systems and is focused on the oxidation reactions catalyzed by ruthenium porphyrins performed in the author's laboratory. A series of ruthenium porphyrin catalysts, including those immobilized onto insoluble supports and covalently attached to soluble supports, promote the oxidation of a wide variety of organic substrates such as styrenes, cycloalkenes, alpha,beta-unsaturated ketones, steroids, benzylic hydrocarbons and arenes with 2,6-dichloropyridine-N-oxide or air in up to >99% yields, with high regio-, chemo- and/or stereoselectivity, and with product turnovers of up to 3.0x10(4), demonstrating the potential application of ruthenium porphyrin-based oxidation systems in organic syntheses.