Editorial

3 pages, 180 KiB

Open AccessEditorial

Editorial: Special Issue on “Flavin Monooxygenases”

by Gianfranco Gilardi and Sheila J. Sadeghi

Catalysts 2021, 11(1), 69; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11010069 - 06 Jan 2021

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Flavin-containing monooxygenase are a large family of enzymes involved in an array of different reactions by activating molecular oxygen and transferring one atom of oxygen to their substrates [...] Full article

(This article belongs to the Special Issue Flavin Monooxygenases)

Research

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12 pages, 7005 KiB

Open AccessArticle

Immobilized Cell Physiology Imaging and Stabilization of Enzyme Cascade Reaction Using Recombinant Cells Escherichia coli Entrapped in Polyelectrolyte Complex Beads by Jet Break-Up Encapsulator

by Marek Bučko, Peter Gemeiner, Tomáš Krajčovič, Marietta Hakarová, Dušan Chorvát, Alžbeta Marček Chorvátová, Igor Lacík, Florian Rudroff and Marko D. Mihovilovič

Catalysts 2020, 10(11), 1288; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10111288 - 05 Nov 2020

Cited by 2 | Viewed by 1974

Abstract

A novel, high performance, and scalable immobilization protocol using a laminar jet break-up technique was developed for the production of polyelectrolyte complex beads with entrapped viable Escherichia coli cells expressing an enzyme cascade of alcohol dehydrogenase, enoate reductase, and cyclohexanone monooxygenase. A significant [...] Read more.

A novel, high performance, and scalable immobilization protocol using a laminar jet break-up technique was developed for the production of polyelectrolyte complex beads with entrapped viable Escherichia coli cells expressing an enzyme cascade of alcohol dehydrogenase, enoate reductase, and cyclohexanone monooxygenase. A significant improvement of operational stability was achieved by cell immobilization, which was manifested as an almost two-fold higher summative product yield of 63% after five cascade reaction cycles as compared to the yield using free cells of 36% after the maximum achievable number of three cycles. Correspondingly, increased metabolic activity was observed by multimodal optical imaging in entrapped cells, which was in contrast to a complete suppression of cell metabolism in free cells after five reaction cycles. Additionally, a high density of cells entrapped in beads had a negligible effect on bead permeability for low molecular weight substrates and products of cascade reaction. Full article

(This article belongs to the Special Issue Flavin Monooxygenases)

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15 pages, 3521 KiB

Open AccessArticle

Insights into the Mechanism of Ethionamide Resistance in Mycobacterium tuberculosis through an in silico Structural Evaluation of EthA and Mutants Identified in Clinical Isolates

by Vinicius Carius de Souza, Deborah Antunes, Lucianna H.S. Santos, Priscila Vanessa Zabala Capriles Goliatt, Ernesto Raul Caffarena, Ana Carolina Ramos Guimarães and Teca Calcagno Galvão

Catalysts 2020, 10(5), 543; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10050543 - 14 May 2020

Cited by 3 | Viewed by 2735

Abstract

Mutation in the ethionamide (ETH) activating enzyme, EthA, is the main factor determining resistance to this drug, used to treat TB patients infected with MDR and XDR Mycobacterium tuberculosis isolates. Many mutations in EthA of ETH resistant (ETH-R) isolates have been described but [...] Read more.

Mutation in the ethionamide (ETH) activating enzyme, EthA, is the main factor determining resistance to this drug, used to treat TB patients infected with MDR and XDR Mycobacterium tuberculosis isolates. Many mutations in EthA of ETH resistant (ETH-R) isolates have been described but their roles in resistance remain uncharacterized, partly because structural studies on the enzyme are lacking. Thus, we took a two-tier approach to evaluate two mutations (Y50C and T453I) found in ETH-R clinical isolates. First, we used a combination of comparative modeling, molecular docking, and molecular dynamics to build an EthA model in complex with ETH that has hallmark features of structurally characterized homologs. Second, we used free energy computational calculations for the reliable prediction of relative free energies between the wild type and mutant enzymes. The ΔΔG values for Y50C and T453I mutant enzymes in complex with FADH₂-NADP-ETH were 3.34 (+/−0.55) and 8.11 (+/−0.51) kcal/mol, respectively, compared to the wild type complex. The positive ΔΔG values indicate that the wild type complex is more stable than the mutants, with the T453I complex being the least stable. These are the first results shedding light on the molecular basis of ETH resistance, namely reduced complex stability of mutant EthA. Full article

(This article belongs to the Special Issue Flavin Monooxygenases)

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13 pages, 2408 KiB

Open AccessArticle

Natural Variation in the ‘Control Loop’ of BVMO_AFL210 and Its Influence on Regioselectivity and Sulfoxidation

by Carmien Tolmie, Rodolpho do Aido-Machado, Felix Martin Ferroni, Martha Sophia Smit and Diederik Johannes Opperman

Catalysts 2020, 10(3), 339; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10030339 - 19 Mar 2020

Cited by 3 | Viewed by 3237

Abstract

Baeyer-Villiger monooxygenases (BVMOs) are flavin-dependent enzymes that primarily convert ketones to esters, but can also catalyze heteroatom oxidation. Several structural studies have highlighted the importance of the ‘control loop’ in BVMOs, which adopts different conformations during catalysis. Central to the ‘control loop’ is [...] Read more.

Baeyer-Villiger monooxygenases (BVMOs) are flavin-dependent enzymes that primarily convert ketones to esters, but can also catalyze heteroatom oxidation. Several structural studies have highlighted the importance of the ‘control loop’ in BVMOs, which adopts different conformations during catalysis. Central to the ‘control loop’ is a conserved tryptophan that has been implicated in NADP(H) binding. BVMO_AFL210 from Aspergillus flavus, however, contains a threonine in the equivalent position. Here, we report the structure of BVMO_AFL210 in complex with NADP⁺ in both the ‘open’ and ‘closed’ conformations. In neither conformation does Thr513 contact the NADP⁺. Although mutagenesis of Thr513 did not significantly alter the substrate scope, changes in peroxyflavin stability and reaction rates were observed. Mutation of this position also brought about changes in the regio- and enantioselectivity of the enzyme. Moreover, lower rates of overoxidation during sulfoxidation of thioanisole were also observed. Full article

(This article belongs to the Special Issue Flavin Monooxygenases)

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20 pages, 3614 KiB

Open AccessArticle

Unique Features of a New Baeyer–Villiger Monooxygenase from a Halophilic Archaeon

by Mattia Niero, Irene Righetto, Elisa Beneventi, Patrizia Polverino de Laureto, Marco Wilhelmus Fraaije, Francesco Filippini and Elisabetta Bergantino

Catalysts 2020, 10(1), 128; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10010128 - 16 Jan 2020

Cited by 7 | Viewed by 3739

Abstract

Type I Baeyer–Villiger monooxygenases (BVMOs) are flavin-dependent monooxygenases that catalyze the oxidation of ketones to esters or lactones, a reaction otherwise performed in chemical processes by employing hazardous and toxic peracids. Even though various BVMOs are extensively studied for their promising role in [...] Read more.

Type I Baeyer–Villiger monooxygenases (BVMOs) are flavin-dependent monooxygenases that catalyze the oxidation of ketones to esters or lactones, a reaction otherwise performed in chemical processes by employing hazardous and toxic peracids. Even though various BVMOs are extensively studied for their promising role in industrial biotechnology, there is still a demand for enzymes that are able to retain activity at high saline concentrations. To this aim, and based on comparative in silico analyses, we cloned HtBVMO from the extremely halophilic archaeon Haloterrigena turkmenica DSM 5511. When expressed in standard mesophilic cell factories, proteins adapted to hypersaline environments often behave similarly to intrinsically disordered polypeptides. Nevertheless, we managed to express HtBVMO in Escherichia coli and could purify it as active enzyme. The enzyme was characterized in terms of its salt-dependent activity and resistance to some water–organic-solvent mixtures. Although HtBVMO does not seem suitable for industrial applications, it provides a peculiar example of an alkalophilic and halophilic BVMO characterized by an extremely negative charge. Insights into the behavior and structural properties of such salt-requiring may contribute to more efficient strategies for engineering the tuned stability and solubility of existing BVMOs. Full article

(This article belongs to the Special Issue Flavin Monooxygenases)

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Review

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21 pages, 2048 KiB

Open AccessReview

The “Green” FMOs: Diversity, Functionality and Application of Plant Flavoproteins

by Sara Thodberg and Elizabeth H. Jakobsen Neilson

Catalysts 2020, 10(3), 329; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10030329 - 14 Mar 2020

Cited by 25 | Viewed by 5783

Abstract

Flavin-dependent monooxygenases (FMOs) are ancient enzymes present in all kingdoms of life. FMOs typically catalyze the incorporation of an oxygen atom from molecular oxygen into small molecules. To date, the majority of functional characterization studies have been performed on mammalian, fungal and bacterial [...] Read more.

Flavin-dependent monooxygenases (FMOs) are ancient enzymes present in all kingdoms of life. FMOs typically catalyze the incorporation of an oxygen atom from molecular oxygen into small molecules. To date, the majority of functional characterization studies have been performed on mammalian, fungal and bacterial FMOs, showing that they play fundamental roles in drug and xenobiotic metabolism. By contrast, our understanding of FMOs across the plant kingdom is very limited, despite plants possessing far greater FMO diversity compared to both bacteria and other multicellular organisms. Here, we review the progress of plant FMO research, with a focus on FMO diversity and functionality. Significantly, of the FMOs characterized to date, they all perform oxygenation reactions that are crucial steps within hormone metabolism, pathogen resistance, signaling and chemical defense. This demonstrates the fundamental role FMOs have within plant metabolism, and presents significant opportunities for future research pursuits and downstream applications. Full article

(This article belongs to the Special Issue Flavin Monooxygenases)

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19 pages, 2869 KiB

Open AccessReview

Enzymatically Produced Trimethylamine N-Oxide: Conserving It or Eliminating It

by Gianluca Catucci, Giulia Querio, Sheila J. Sadeghi, Gianfranco Gilardi and Renzo Levi

Catalysts 2019, 9(12), 1028; https://0-doi-org.brum.beds.ac.uk/10.3390/catal9121028 - 04 Dec 2019

Cited by 9 | Viewed by 4183

Abstract

Trimethylamine N-Oxide (TMAO) is the product of the monooxygenation reaction catalyzed by a drug-metabolizing enzyme, human flavin-containing monooxygenase 3 (hFMO3), and its animal orthologues. For several years, researchers have looked at TMAO and hFMO3 as two distinct molecules playing specific but separate roles, [...] Read more.

Trimethylamine N-Oxide (TMAO) is the product of the monooxygenation reaction catalyzed by a drug-metabolizing enzyme, human flavin-containing monooxygenase 3 (hFMO3), and its animal orthologues. For several years, researchers have looked at TMAO and hFMO3 as two distinct molecules playing specific but separate roles, the former to defend saltwater animals from osmotic or hydrostatic stress and the latter to process xenobiotics in men. The presence of high levels of plasmatic TMAO in elasmobranchs and other animals was demonstrated a long time ago, whereas the actual physiological role of hFMO3 is still unknown because the enzyme has been mainly characterized for its ability to oxidize drugs. Recently TMAO was found to be related to several human health conditions such as atherosclerosis, cardiovascular, and renal diseases. This correlation poses a striking question of how other vertebrates (and invertebrates) can survive in the presence of very high TMAO concentrations (micromolar in humans, millimolar in marine mammals and several hundred millimolar in elasmobranchs). Therefore, it is important to address how TMAO, its precursors, and FMO catalytic activity are interconnected. Full article

(This article belongs to the Special Issue Flavin Monooxygenases)

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19 pages, 1004 KiB

Open AccessReview

Endogenous Roles of Mammalian Flavin-Containing Monooxygenases

by Ian R. Phillips and Elizabeth A. Shephard

Catalysts 2019, 9(12), 1001; https://0-doi-org.brum.beds.ac.uk/10.3390/catal9121001 - 28 Nov 2019

Cited by 8 | Viewed by 3645

Abstract

Flavin-containing monooxygenases (FMOs) catalyze the oxygenation of numerous foreign chemicals. This review considers the roles of FMOs in the metabolism of endogenous substrates and in physiological processes, and focuses on FMOs of human and mouse. Tyramine, phenethylamine, trimethylamine, cysteamine, methionine, lipoic acid and [...] Read more.

Flavin-containing monooxygenases (FMOs) catalyze the oxygenation of numerous foreign chemicals. This review considers the roles of FMOs in the metabolism of endogenous substrates and in physiological processes, and focuses on FMOs of human and mouse. Tyramine, phenethylamine, trimethylamine, cysteamine, methionine, lipoic acid and lipoamide have been identified as endogenous or dietary-derived substrates of FMOs in vitro. However, with the exception of trimethylamine, the role of FMOs in the metabolism of these compounds in vivo is unclear. The use, as experimental models, of knockout-mouse lines deficient in various Fmo genes has revealed previously unsuspected roles for FMOs in endogenous metabolic processes. FMO1 has been identified as a novel regulator of energy balance that acts to promote metabolic efficiency, and also as being involved in the biosynthesis of taurine, by catalyzing the S-oxygenation of hypotaurine. FMO5 has been identified as a regulator of metabolic ageing and glucose homeostasis that apparently acts by sensing or responding to gut bacteria. Thus, FMOs do not function only as xenobiotic-metabolizing enzymes and there is a risk that exposure to drugs and environmental chemicals that are substrates or inducers of FMOs would perturb the endogenous functions of these enzymes. Full article

(This article belongs to the Special Issue Flavin Monooxygenases)

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