Reactions Catalyzed by Bacterial Cytochromes P450

2003 ◽  
Vol 56 (8) ◽  
pp. 749 ◽  
Author(s):  
Max J. Cryle ◽  
Jeanette E. Stok ◽  
James J. De Voss
Keyword(s):  
Bond Cleavage ◽  
Cytochromes P450 ◽  
Large Family ◽  
Practical Application ◽  
Bacterial Enzymes ◽  
Aromatic Hydroxylation ◽  
Oxidizing Power ◽  
Oxidative Transformations ◽  
Multiple Oxidations

The cytochromes P450 are a large family of oxidative haemoproteins that are responsible for a wide variety of oxidative transformations in a variety of organisms. This review focuses upon the reactions catalyzed specifically by bacterial enzymes, which includes aliphatic hydroxylation, alkene epoxidation, aromatic hydroxylation, oxidative phenolic coupling, heteroatom oxidation and dealkylation, and multiple oxidations including C–C bond cleavage. The potential for the practical application of the oxidizing power of these enzymes is briefly discussed.

scholarly journals Characterization of O-demethylations and Aromatic Hydroxylations Mediated by Cytochromes P450 in the Metabolism of Flavonoid Aglycons

2019 ◽  
Vol 92 (1) ◽  
pp. 115-123 ◽  
Author(s):  
Goran Benković ◽  
Hrvoje Rimac ◽  
Željan Maleš ◽  
Siniša Tomić ◽  
Zoran Lončar ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Human Liver ◽  
Cytochromes P450 ◽  
Liver Microsomes ◽  
Cytochrome P450 Enzymes ◽  
Uv Detector ◽  
Aromatic Hydroxylation ◽  
Metabolism Of Xenobiotics ◽  
Kinetics Of

One of the most important groups of metabolic enzymes is cytochrome P450 superfamily. These enzymes are important in terms of the catalytic diversity and the large number of xenobiotics that are detoxified or activated by converting to reactive metabolites. Flavonoids are xenobiotics to which humans are exposed through diet. Data on their oxidative metabolism mediated by cytochromes P450 are limited. The aim of this study was to determine the enzymatic kinetics of O-demethylation and aromatic hydroxylation of flavonoid aglycons on recombinant cytochrome P450 enzymes and human liver microsomes systems. The study was performed on ten flavonoids, namely 3,7-dihydroxyflavone, 7-hydroxyflavone, acacetin, apigenin, flavone, galangin, kaempferol, naringenin, sakuranetin, and tangeretin using liquid chromatography coupled with mass spectrometry and UV detector. Most relevant enzyme involved in metabolism of flavonoid aglycons is CYP1A2, and its catalytic effectiveness ranges from 0.5 to 2.9 × 106 M–1 min–1. Having in mind high expression and involvement of CYP1A2 in metabolism of xenobiotics including drugs, and its intraindividual differences in expression and activity, potential of drug-flavonoid competitive interactions/inhibitions should be considered when consuming dietary supplement and foods rich in flavonoids.

The Clearance of Thrombin-antithrombin and Related Serpin-enzyme Complexes from the Circulation: Role of Various Hepatocyte Receptors

1999 ◽  
Vol 81 (03) ◽  
pp. 325-337 ◽  
Author(s):  
Michael Wells ◽  
William Sheffield ◽  
Morris Blajchman
Keyword(s):  
Bond Cleavage ◽  
Large Body ◽  
Large Family ◽  
Peptide Bond ◽  
Active Enzyme ◽  
Heparin Cofactor Ii ◽  
Peptide Bond Cleavage ◽  
Reactive Centre Loop ◽  
Ester Linkage ◽  
Suicide Inhibitors

IntroductionPeptide bond cleavage can herald the end of a protein’s active life, or its transformation from an inactive precursor to an active enzyme. If the newly activated protein is a proteinase, even a highly specific proteinase, then its activity must be regulated in order that unbridled cleavage and damage to the host organism do not ensue. Such regulation for many of the key serine proteinases of the coagulation, fibrinolytic, complement, and inflammatory pathways is provided by the inhibitory proteins of the serpin family.The serpins are a large family of over 100 proteins (1). Many are plasma proteins such as antithrombin (AT), α1-proteinase inhibitor (α-PI), α1-antichymotrypsin (α-AC), heparin cofactor II (HCII), plasminogen activator inhibitors (PAI) I and II, α2-antiplasmin (α2-AP) and proteinase nexin I (PN-1). While some serpins are readily recognizable as family members, solely by virtue of homology, others have been characterized in detail, particularly those that are suicide inhibitors of their cognate proteinases; enzymes that recognize and attack the reactive centre loop of the inhibitory serpins. The resulting serpin-enzyme complex (SEC) is comprised of the inhibitor, which is irreversibly inactivated by virtue of the cleavage of its reactive centre peptide bond, and the enzyme, which is reversibly inactivated by the formation of an acyl ester linkage between its active site serine and a serpin side chain. Thus, a stable, covalent, and stoichiometric complex resistant to denaturation is formed (2, 3).The reversible nature of the proteinase’s inactivation in the SEC means that while substantial regulation of the proteinase has been achieved, the organism has only prolonged the inevitable by forming the SEC. Because the SEC is only kinetically but not thermodynamically stable, given sufficient time it will break down, releasing cleaved serpin and active enzyme (4, 5). To prevent this, receptor-mediated mechanisms have evolved to effectively remove SECs from the circulation. Since the initial studies of Ohlsson, who investigated the clearance of α-PI-trypsin complexes in the circulation of dogs (6, 7), a large body of evidence has accumulated to indicate that SECs are cleared from the circulation more rapidly than their constituent serpins. This accelerated clearance seals the fate of the serpin-complexed proteinases, and prevents their release from SECs by sequestering the SECs inside cells, where they are catabolized. In this article, we review the available data with respect to the mechanisms involved in SEC removal from the circulation. Specifically, we address those proteins or molecules that have been reported to act as cellular receptors for SEC removal, and propose a model for SEC removal which includes several of the available candidate receptors. Where possible, we have focussed on the thrombin-antithrombin (TAT) complex, both because of our laboratory’s longstanding interest in antithrombin, and because of thrombin’s key role in haemostasis and thrombosis (8).

scholarly journals Catalytic Mechanisms of Fe(II)- and 2-Oxoglutarate-dependent Oxygenases

2015 ◽  
Vol 290 (34) ◽  
pp. 20702-20711 ◽  
Author(s):  
Salette Martinez ◽  
Robert P. Hausinger
Keyword(s):  
Family Members ◽  
Large Family ◽  
Ring Formation ◽  
Oxidative Transformations ◽  
Catalytic Mechanisms

Mononuclear non-heme Fe(II)- and 2-oxoglutarate (2OG)-dependent oxygenases comprise a large family of enzymes that utilize an Fe(IV)-oxo intermediate to initiate diverse oxidative transformations with important biological roles. Here, four of the major types of Fe(II)/2OG-dependent reactions are detailed: hydroxylation, halogenation, ring formation, and desaturation. In addition, an atypical epimerization reaction is described. Studies identifying several key intermediates in catalysis are concisely summarized, and the proposed mechanisms are explained. In addition, a variety of other transformations catalyzed by selected family members are briefly described to further highlight the chemical versatility of these enzymes.

Interactions of Peroxyquinols with Cytochromes P450 2B1, 3A1, and 3A5 - Influence of the Apoprotein on Heterolytic Versus Homolytic O-O Bond-Cleavage

1995 ◽  
Vol 317 (2) ◽  
pp. 471-478 ◽  
Author(s):  
M.A. Correia ◽  
K.Q. Yao ◽  
A.J. Allentoff ◽  
S.A. Wrighton ◽  
J.A. Thompson
Keyword(s):  
Bond Cleavage ◽  
Cytochromes P450

Selectivity in a barren landscape: the P450BioI–ACP complex

2010 ◽  
Vol 38 (4) ◽  
pp. 934-939 ◽  
Author(s):  
Max J. Cryle
Keyword(s):  
Fatty Acid ◽  
Protein Complex ◽  
Acyl Carrier Protein ◽  
Protein Complexes ◽  
Cytochromes P450 ◽  
Carrier Protein ◽  
Pimelic Acid ◽  
Fatty Acid Chain ◽  
Fatty Acid Hydroxylation ◽  
Oxidative Transformations

The cytochromes P450 (P450s) are a superfamily of oxidative haemoproteins that are capable of catalysing a vast range of oxidative transformations, including the oxidation of unactivated alkanes, often with high stereo- and regio-selectivity. Fatty acid hydroxylation by P450s is widespread across both bacteria and higher organisms, with the sites of oxidation and specificity of oxidation varying from system to system. Several key examples are discussed in the present article, with the focus on P450BioI (CYP107H1), a biosynthetic P450 found in the biotin operon of Bacillus subtilis. The biosynthetic function of P450BioI is the formation of pimelic acid, a biotin precursor, via a multiple-step oxidative cleavage of long-chain fatty acids. P450BioI is a member of an important subgroup of P450s that accept their substrates not free in solution, but rather presented by a separate carrier protein. Structural characterization of the P450BioI–ACP (acyl-carrier protein) complex has recently been performed, which has revealed the basis for the oxidation of the centre of the fatty acid chain. The P450BioI–ACP structure is the first such P450–carrier protein complex to be characterized structurally, with important implications for other biosynthetically intriguing P450–carrier protein complexes.

scholarly journals Complete σ* intramolecular aromatic hydroxylation mechanism through O2 activation by a Schiff base macrocyclic dicopper(I) complex

2013 ◽  
Vol 9 ◽  
pp. 585-593 ◽  
Author(s):  
Albert Poater ◽  
Miquel Solà
Keyword(s):  
Schiff Base ◽  
Proton Transfer ◽  
Dft Calculations ◽  
Reaction Pathway ◽  
Bond Cleavage ◽  
Bond Formation ◽  
Subsequent Reaction ◽  
O2 Activation ◽  
Aromatic Carbon ◽  
Aromatic Hydroxylation

In this work we analyze the whole molecular mechanism for intramolecular aromatic hydroxylation through O2 activation by a Schiff hexaazamacrocyclic dicopper(I) complex, [CuI 2(bsH2m)]2+. Assisted by DFT calculations, we unravel the reaction pathway for the overall intramolecular aromatic hydroxylation, i.e., from the initial O2 reaction with the dicopper(I) species to first form a CuICuII-superoxo species, the subsequent reaction with the second CuI center to form a μ-η2:η2-peroxo-CuII 2 intermediate, the concerted peroxide O–O bond cleavage and C–O bond formation, followed finally by a proton transfer to an alpha aromatic carbon that immediately yields the product [CuII 2(bsH2m-O)(μ-OH)]2+.

scholarly journals Screening of flavonoid aglycons’ metabolism mediated by the human liver cytochromes P450

2019 ◽  
Vol 69 (4) ◽  
pp. 541-562 ◽  
Author(s):  
Goran Benković ◽  
Mirza Bojić ◽  
Željan Maleš ◽  
Siniša Tomić
Keyword(s):  
Human Liver ◽  
High Performance ◽  
High Resolution Mass Spectrometry ◽  
Biological Effects ◽  
Cytochromes P450 ◽  
Liver Microsomes ◽  
Recombinant Enzymes ◽  
Aromatic Hydroxylation ◽  
Metabolic Reactions

Abstract Biological effects of flavonoids have been extensively studied in the last 80 years. As flavonoids represent a rather large group of compounds, data on metabolic biotransformations of these compounds is relatively limited to those well studied. The objective of this study was to screen the metabolism of 30 selected flavonoid aglycons mediated by the most relevant metabolic enzymes, human liver cytochromes P450. For this purpose, in vitro experiments with human liver microsomes and recombinant enzymes were conducted. To evaluate flavonoid’s metabolism and structure of the products, high-performance liquid chromatography coupled with high-resolution mass spectrometry was used. Out of 30 flavonoids, 15 were susceptible to oxidative metabolism mediated by cytochromes P450. Dominant reactions were aromatic hydroxylation and O-demethylation, or a combination of these reactions. The dominant enzyme responsible for the observed metabolic reactions is CYP1A2, whereas other human liver cytochromes P450, namely, CYP2C19, CYP2D6, CYP2E1 and CYP3A4, contribute to flavonoid metabolism to a lesser degree. These results, to some extent, contribute to the understanding of the metabolism of constituents found in antioxidant dietary supplements and their possible interactions with other xenobiotics, i.e., medicinal products.

scholarly journals A requirement for an active proton delivery network supports a compound I-mediated C–C bond cleavage in CYP51 catalysis

2020 ◽  
Vol 295 (29) ◽  
pp. 9998-10007 ◽  
Author(s):  
Tatiana Y. Hargrove ◽  
Zdzislaw Wawrzak ◽  
F. Peter Guengerich ◽  
Galina I. Lepesheva
Keyword(s):  
Bond Cleavage ◽  
Cytochromes P450 ◽  
Relay Network ◽  
Compound I ◽  
X Ray ◽  
Proton Relay ◽  
Multistep Reactions ◽  
Biochemical Analyses ◽  
Ferric Peroxo ◽  
Delivery Network

CYP51 enzymes (sterol 14α-demethylases) are cytochromes P450 that catalyze multistep reactions. The CYP51 reaction occurs in all biological kingdoms and is essential in sterol biosynthesis. It removes the 14α-methyl group from cyclized sterol precursors by first forming an alcohol, then an aldehyde, and finally eliminating formic acid with the introduction of a Δ14–15 double bond in the sterol core. The first two steps are typical hydroxylations, mediated by an electrophilic compound I mechanism. The third step, C–C bond cleavage, has been proposed to involve either compound I (i.e. FeO3+) or, alternatively, a proton transfer-independent nucleophilic ferric peroxo anion (compound 0, i.e. Fe3+O2–). Here, using comparative crystallographic and biochemical analyses of WT human CYP51 (CYP51A1) and its D231A/H314A mutant, whose proton delivery network is destroyed (as evidenced in a 1.98-Å X-ray structure in complex with lanosterol), we demonstrate that deformylation of the 14α-carboxaldehyde intermediate requires an active proton relay network to drive the catalysis. These results indicate a unified, compound I-based mechanism for all three steps of the CYP51 reaction, as previously established for CYP11A1 and CYP19A1. We anticipate that our approach can be applied to mechanistic studies of other P450s that catalyze multistep reactions, such as C–C bond cleavage.

scholarly journals Aromatic hydroxylation of salicylic acid and aspirin by human cytochromes P450

2015 ◽  
Vol 73 ◽  
pp. 49-56 ◽  
Author(s):  
Mirza Bojić ◽  
Carl A. Sedgeman ◽  
Leslie D. Nagy ◽  
F. Peter Guengerich
Keyword(s):  
Salicylic Acid ◽  
Cytochromes P450 ◽  
Aromatic Hydroxylation
Sign in / Sign up

Export Citation Format

Share Document